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Department of Civil Engineering
October, 2005
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111111111111111111111111111 1111~I--#100953#
A Thesis Submitted by
Selim Ahamed
In partial fulfillment of the requirement for the degree of
MASTER OF SCIENCE IN CIVIL ENGINEERING
BANGLADESH UNIVERSITY OF ENGINEERING AND TECHNOLOGY
Soil Characteristics and Liquefaction Potential
of Selected Reclaimed Areas of Dhaka City
The thesis titled Soil Characteristics and Liquefaction Potential of Selected
Reclaimed Areas of Dhaka City, submitted by Selim Ahamed, Roll No. 040304201P,
Session April 2003 has been accepted as satisfactory in partial fulfillment of the
requirement for the degree of Master of Science in Civil Engineering on October
2005.
BOARD OF EXAMINEERS
,.'.'.,
Member
Member(External)
Member(Ex-Officio)
Member
Chairman(Supervisor)
~Dr. Md. Mazharul HoqueProfessor and HeadDepartment of Civil EngineeringBUET, Dhaka-lOOO
~~/Md.~dul IslamChie EngineerRAJUK, Dhaka
.~Dr. Mohammad Shariful IslamAssistant ProfessorDepartment of Civil EngineeringBUET, Dhaka-lOOO
/Li i\kdr, Syed Fakhrul AmeenProfessorDepartment of Civil EngineeringBUET, Dhaka-lOOO
D~---ProfessorDepartment of Civil Engineering.BUET, Dhaka-lOOO
DECLARATION
It is hereby declared that except for the contents where specific references have been
made to the work of others, the studies contained in this thesis are the result of
investigation carried out by the author under the supervision of Dr. Mohammad
Shariful Islam, Assistant Professor, Department of Civil Engineering, Bangladesh
University of Engineering and Technology.
No part of this thesis has been submitted to any other university or other educational
establishments for a degree, diploma or other qualifications (except for publication).
(Signature of the Author)
11
ACKNOWLEDGEMENT
Thanks to the Omnipotent Allah for his graciousness, kindness and blessings forallowing me to do this work without which nothing happens in this world.
The author wishes to express his deepest gratitude to his supervisor, Dr. MohammadShariful Islam, Assistant Professor, Department of Civil Engineering, BUET for hisincessant support and guidance without which this thesis work would not come intoreality. His continuous direction, advice and help to choose such a topic encouragedthe author all through. The author specially thanks the supervisor for his guidanceand presence during the field work in and around Dhaka City and his continuousefforts for data collection from different agencies.
The author wants to express his sincere thanks to Dr. Md. Mazharul Hoque,Professor and Head, Department of Civil Engineering, BUET, for his co-operation.
The author wishes to express sincere appreciation to Dr. Syed Fakhrul Ameen, andDr. Eqramul Hoque, Professors, Department of Civil Engineering, BUET for theirinterest and suggestions during the present research.
Profound appreciation is due to Mr. Mohamamd Emdadul Islam, Chief Engineer,Rajdani Unnon Kartipakkha (RAJUK), Dhaka for his deepest assistance in datacollection and suggestions about the research work.
The author would like to express his gratitude and appreciation to all of those whoextended their kind assistance and co-operation during the course of the research.The author would like to express his gratitude to Mr. Shoaib, Executive Engineer,Bashundhara Group, Mr. Masud, Managing Director, ICON Engineering, Mr.Shahajahan, Director, Unique Boring, Brg. Enamul Hoque, Mr. Kamal Uddin forgiving data and permission for boring.
The author express his gratitude to Mr. Jahangir Alam, Managing Director, DataExpert and Farjana Alam, undergraduate student of URP, BUET for their helping toprepare the reclaimed area map of Dhaka city and Keraniganj, respectively.
The author is indebted to his colleagues specially Mr. Saha, Mr. Rashid, Mr. Borhan,Mr. Kaykobad, Mr. Sadek and Mr. Shamim for supporting him all the time withinspiration during this research.
Thanks are expressed to laboratory staffs of Geotechnical Engineering Division,Department of Civil Engineering, BUET for helping the author during the collectionand analysis of samples and for accompanying in field investigation and laboratorytests. All other skilled and non-skilled persons who helped during the work are alsoacknowledged.
Finally, the author wishes to thank his parents for their continuous support in thisstudy.
111
ABSTRACT
Reclaimed areas are being developed in and around Dhaka city in Bangladesh byfilling low lands. There are four methods for developing such areas in practice. Ingeneral, soil is collected from riverbeds by cutter-suction dredging into a barge,which is carried to the nearest river site. Soil is then pumped through pipes in a slurryform mixing with water, and transferred to the point of deposition. However, in thismethod of filling, segregation of particles occurs. Dredged materials are collectedfrom riverbed and riverbanks of the rivers near the city. It was found that mean grainsize, fines content, uniformity coefficient and fineness modulus of the sourcematerials for developing such areas varied from 0.002 to 0.34 mm, 2 to 15%, 2.60 to4.30 and 0.15 to 1.45, respectively.
Field density tests were conducted near the surface at two reclaimed sites of Dhakacity. It was observed that the field density varied from 12.84 to 17.54 kN/m3.
Relative density (Dr) of the samples varied from 29 to 107%. However, the relativedensity was more than 50% in general.
About one hundred borehole data had been collected from different government andnon-government agencies and sixteen borings were conducted. It was found thatground water table exists 1.5 to 2.5 m below existing growld level (EGL). Fillingdepth found to vary from 3 to 8 m. The SPT N-value of the filling depth varied from1 to 13. In most cases, the soil was silty sand up to filling depth of reclaimed sites.The soil beneath the fill varied significantly. The variability in sub-soilcharacteristics indicates that the detailed sub-soil investigation is necessary forproper foundation design in such areas.
Liquefaction potential analysis was conducted at 38 locations based on JapaneseCode of Bridge Design and Chinese Criterion. The liquefaction potential analysiswas not conducted at otller locations as the soil of those locations was clayey type.The value of peak horizontal acceleration, amax was taken as O.l5g according toseismic micro zonation map of Bangladesh. According to Japanese Code of BridgeDesign, there are only two locations where liquefiable depth exists. Liquefiable depthof those locations is 2.5 to 5.0 m and 5.0 m from EGL. On the other hand, accordingto Chinese Criterion, there are 28 locations where liquefiable depth exists. Theliquefiable depth varied from 2.0 to 13.0 m from EGL. However, the liquefactionpotential determined by Chinese Criterion does not consider the effects of finescontent. It is clear that the liquefaction potential of such areas in Dhaka city is lowbecause the filling soil has fines. But, the presence of fines in the hydraulic fill meansgreater compressibility and difficulty in compaction. It also reduce permeability andhence the rate of drainage.
Relative density tests can be conducted at larger depths to determine correlationbetween Dr and SPT N-value. Laboratory tests can be conducted to determine thecyclic strengths of the soils. More detailed study can be conducted to determine theliquefaction potential precisely using other methods and models. Liquefactionpotential map of the areas can be determined using the results obtained in this study.
Keywords: Reclaimed area, soil characteristics, liquefaction potential.
IV
1.1 General
1.2 Seismicity of Bangladesh 21.3 Liquefaction and Its Significance 71.4 Study Background 81.5 Scopes and Objectives 81.6 The Research Scheme 91.7 Overview of Research Program 11
CHAPTER 2 LITERATURE REVIEW
2.1 General 132.2 Past Researches Related to Liquefaction 132.3 Seismic Zoning Map of Bangladesh 202.4 Case Studies 212.5 Liquefaction - induced Damages 262.6 Stratigraphy of Liquefiable Ground 282.7 Remediation of Liquefiable Ground 29
2.7.1 Conventional Approach 29
v
ix
XV
Xl
Page
ii
iii
iv
TABLE OF CONTENTS
v
INTRODUCTION
DECLARATION
ACKNOWLEDGEMENT
ABSTRACT
TABLE OF CONTENTS
LIST OF TABLES
LIST OF FIGURES
NOTATIONS
CHAPTER I
CHAPTER 3
2.7.2 Generalized Approach 312.8 Measures Against Liquefaction 33
2.8.1 Avoid Liquefaction Susceptible Soils 352.8.2 Improvement of the Soil 352.8.3 Liquefaction Resistant Structure 37
2.9 Probability of Liquefaction 382.10 Assessment of Liquefaction Potential 39
2.10.1 Prediction of Liquefaction 392.10.2 Cyclic Strength of Soils 422.10.3 Conditions for Liquefaction to Occur 442.10.4 Liquefaction Susceptibility 442.10.5 Steps in Liquefaction Prediction 452.10.6 Liquefaction Potential Analysis 472.10.7 Estimation of Liquefaction Susceptibility 48
Using Different Methods
2.10.8 Liquefaction Criteria For Fine Grained 50Soils
2.10.9 Liquefaction Potential Analysis Based on 50SPT N-Value Using Different Methods
DEVELOPMENT OF RECLAIMED AREAS IN DHAKA CITY
3.1 General 663.2 Reclaimed Areas in Dhaka City 673.3 Sources of Filling Material 703.4 Criteria for Fill Material 703.5 Characteristics of Source Material 723.6 Filling Procedure 783.7 Proposal for Rational Land Development Procedure 813.8 Summary 82
VI
4.1 General 834.2 Selected Reclaimed Areas 834.3 Field and Laboratory Investigations 84
4.3.1 Field Density Test , 844.3.2 Standard Penetration Test 854.3.3 Laboratory Tests 89
4.4 Sub-Soil Characteristics of Reclaimed Areas 914.4.1 Sub-Soil Characteristics of Bashundhara 914.4.2 Sub-Soil Characteristics of Purbachal New 97
Model Town
4.4.3 Sub-Soil Characteristics of Uttar a Model Town 103(Third Phase)
4.4.4 Sub-Soil Characteristics of Mirpur DOHS 1074.4.5 Sub-Soil Characteristics of Banani Old DOHS 110,4.4.6 Sub-Soil Characteristics of Banasree III4.4.7 Sub-Soil Characteristics of Keraniganj 112
4.5 Summary 115
SUB-SOIL CHARACTERISTICS OF RECLAIMED
AREAS IN DHAHA CITY
116
116
117
120
121Liquefaction Potential of Uttara Model
Town (Third Phase)
vii
General
Liquefaction Potential of Reclaimed Areas
5.2.1 Liquefaction Potential of Bashundhara
5.2.2 Liquefaction Poiential of Purbachal New
Model Town
5.2.3
LIQUEFACTION POTENTIAL OF RECLAIMED
AREAS IN DHAKA CITY
5.1
5.2
CHAPTER 4
CHAPTERS
5.2.4 Liquefaction Potential of Mirpor DOHS 123
5.2.5 Liquefaction Potential ofKholamura, 124
Keraniganj
5.2.6 Liquefaction Potential of Banani Old DOHS 126
5.2.7 Liquefaction Potential ofBanasree 126
5.3 Critical N- Value for Liquefaction 126
5.4 Summary 127
CONCLUSIONS AND RECOMMENDATIONS
••
129
129
130
130
131
133
141
150
viii
General
Development of Reclaimed Areas
Sub-soil Characteristics of Reclaimed Areas
Liquefaction Potential of Reclaimed Areas
Scopes for Future Researches
6.1
6.2
6.3
6.46.5
CHAPTER 6
APPENDIX A
APPENDIXB
.REFERANCES
Table 3;3 Characteristics of soil samples collected from different sources 73
Table 3.4 Grain size properties of soil samples collected during dredging 74
from river sources
33
41
41
4
42
48
49
50
64
76
Page
3(BoIt, 1987)
List of major earthquakes affecting Bangladesh during last 150
years (M ;:0: 7) (Subri, 2002)
Maximwn earthquake magnitude in different tectonic blocks
Summary of the liquefaction potential index
Factors affecting the occurrence of liquefaction (JGS, 1998)
Information required for various liquefaction evaluations (JGS,
LIST OF TABLES
1998)
2000)
1988)
Liquefaction susceptibility based on geomorphological units(Yasuda, 1988)
Vulnerable soil properties for liquefaction (Rao, 2003)
Liquefaction criteria for fine-grained soil (Andrew and martin,
IX
Grain size properties of soil samples collected from various
river banks
Soil type in various guidelines requiring liquefaction evaluation
(JGS, 1998)
Liquefaction susceptibility of sedimentary deposits (Yasuda, 46
Table 2.1
Table 2.2
Table 2.3
Table 1.2
Table 1.1
Table 2.4
Table 2.6
Table 2.5
Table 2.7
Table 2.8
Table 2.9 Representative unit weight, mean grain size, and fines content
for various soil types (JRA, 1990 and JSCE, 1986)
Table 2.10 Typical unit weights of soil (Coduto, 2002) 65
Table 2.11 Correlation between relative density and penetration resistance 65(Peck et. aI., 1974)
Table 3.1 Location of reclaimed areas in and around Dhaka city 68
Table 3.2 Quality of dredge fill materials 71
Table 3.5
Table 4.1
Table 4.2
Table 4.3
Table 4.4
Table 4.5
Table 4.6
Table 4.7
Table 4.8
Table 4.9
Table 4;10
Table 4.11
Table 4.12
Table 5.1
Table 5.2
Table 5.3
Table 5.4
Table 5.5
Relative density (Dr) description 85
Recommended SPI procedure (ASTM D1586) 86
Borehole, sampler and correction factors (Skempton, 1986) 89
SPT hammer efficiencies (Clayton, 1990) 89
Factors affecting the SPT (Kulhaway and Mayne, 1990) 90
List of tests conducted 91
Unconfined compression test results of samples collected from 94
Bashundhara area
Field and laboratory density test results of samples collected 99
from Pitolganj, Purbachal
Field and laboratory density test results of samples collected 101
from Brahmnkhali, Purbachal
Unconfined compression test results of samples collected from 102
Purbachal New Model Town
Field and laboratory density test results of samples collected 106
from Dia Bari, Uttara Model Town
Unconfined compression test results of samples collected from 107
Uttara Model Town
Presence ofliquefiable soil strata at Bashundhara site 118
Presence of liquefiable soil strata at Purbachal New Model 120
Town site
Presence of liquefiable soil strata at Uttara Model Town (Third 122
Phase) site
Presence of liquefiable soil strata at Mirpur DOHS site 123
Presence of liquefiable soil strata at Kholamura, Keraniganj 125
site
x .'
LIST OF FIGURES
Figure 1.1
Figure 2.1
Figure 2.2
Figure 2.3
Figure 2.4
Figure 2.5
Figure 2.6
Figure 2.7
Figure 2.8
Figure 2.9
Figure 2.10
Figure 2.11
Figure 2.12
Figure 2.13
Figure 2.14
Figure 2.15
Figure 2.16
Seismic map showing epicenters of historical earthquakes
in and around Bangladesh (Khan, 2004)
Seismic zoning map of Bangladesh (BNBC, 1993)
Seismic zoning map of Bangladesh (Sharfuddin, 200 I)
Borehole data from Adapazari in Turkey (Madabhushi,
2005)
Standard penetration resistance of Niigata sand (Seed and
Idriss, 1982)
Damages due to liquefaction during some past earthquakes
Classification ofliquefiable ground type (JGS, 1998)
Conventional approach for remediation of liquefiable
ground (JGS, 1998)
Generalized approaches to remedial work (JGS, 1998)
Flowchart of simplified method using SPT N-value
(Yoshimi, 1991)
Critical SPT N-value and fines content relation for
liquefiable soils (Yasuda, 1988)
Summary charts for evaluation of the cyclic strength of
sands based on the normalized SPT N-value (Ishihara,
1993)
CN factors by various investigations (ASTM D 1586)
. Definition of an increment of Nlvalue, allowing for the
effects of fines (Ishihara, 1993)
Increment LlNl value as a function of fines content
(Ishihara, 1993)
Effects of plasticity index on the cyclic strength of fines
containing sand (Ishihara, 1993)
Chart for modification of cyclic strength allowing for the
effects of plasticity index (Ishihara, 1993)
Xl
Page
5
22
2324
26
27
2931
32
47
50
54
55
57
58
59
60
.Qr'.,J:"
Figure 2.17
Figure 2.18
Figure 2.19
Figure 3.1
Figure 3.2
Figure 3.3
Figure 3.4
Figure 3.5
Figure 3.6
Figure 3.7
Figure 3.8
Figure 3.9
Figure 4.1
Figure 4.2
Figure 4.3
Figure 4.4
Figure 4.5
Figure 4.6
Figure 4.7
Simplified method for calculating shear/disturbing stress
(Seed and Idriss, 1982)
Range of value of rd for different soil profiles (Seed and
Idriss, 1982)
Time history of shear stresses during earthquake (Seed and
Idriss, 1982)
Location of reclaimed areas in Dhaka City
Permissible range of grain sizes for hydraulic fill to be
used for land filling (Whitman, 1970)
Grain size distributions of samples collected from river
banks and char
Grain size distributions of samples collected from river bed
Grain size distributions of samples collected from river
banks and char
Grain size distributions of samples collected from flver
banks and char
Discharge at pipe head
Filling oflowlands using hydraulic fill
Particle distributions after discharge to filling sites
Approximate locations of bore holes at Bashundhara site
Stress vs strain relationship in unconfined compressive test
at Bashundhara site
(a)Depth versus SPT N-value and (b) Depth versus Dso atBashundhara
(a)Depth versus SPT N-value and (b) Depth versus Dso at
Bashundhara
(a)Depth versus SPT N-value and (b) Depth versus Dso atBashundhara
(a)Depth versus SPT N-value and (b) Depth versus Dso at
Bashundhara
Approximate locations of bore holes at Purbachal New
Model Town
Xli
61
62
63
6972
73
7475
75
79
80
81
92
95
95
96
96
97
98
Figure 4.8
Figure 4.9
Figure 4.10
Figure 4.11
Figure 4.12
Figure 4.13
Figure 4.14
Figure 4.15
Figure 4.16
Figure 4.17
Figure 4.18
Figure 4.19
Figure 4.20
Figure 4.21
Figure 5.1
Figure 5.2
Figure 5.3
Grain size distribution of samples collected from Pitolganj,
Purbachal
Grain size distribution of samples collected from
Brahmankhali, Purbachal
(a) Depth versus SPT N-value and (b) Depth versus D50 at
Purbachal New Model Town
Approximate locations of bore holes at Uttara Model Town
(Third phase)
Grain size distribution of samples collected from Uttara
Model Town
(a) Depth versus SPT N-value and (b) Depth versus D50 at
Uttara Model Town (Third Phase)
Approximation locations of bore holes at Mirpur DHOS
(a) Depth versus SPT N-value and (b) Depth versus D50 at
MirpurDOHS
(a) Depth versus SPT N-value and (b) Depth versus D50 at
MirpurDOHS
(a) Depth versus SPT N-value and (b) Depth versus D50 at
Banani Old DOHS
(a) Depth versus SPT N-value and (b) Depth versus D50 at
Banasree
Approximate locations of bore hole at Kholamura,
Keraniganj
(a) Depth versus SPT N-value and (b) Depth versus D50 at
Kholamura, Keraniganj
qu versus moisture content
Example of liquefaction potential analysis using SPT N-
value
Liquefaction potential vs depth (a) Chinese criterion and
(b) Japanese code at Bashundhara site
Liquefaction potential vs depth (a) Chinese criterion and
(b) Japanese code at Bashundhara site
Xlll
99
100
103
104
105
107
109109
110
111
112
113
114
114
117
119
119
Figure 5.4 Liquefaction potential vs depth (a) Chinese criterion and 121(b) Japanese code at Purbachal New Model Town
Figure 5.5 Liquefaction potential vs depth (a) Chinese criterion and 122(b) Japanese code at Uttara Model Town (Third Phase)
Figure 5.6 Liquefaction potential vs depth (a) Chinese criterion and 124(b) Japanese code at Mirpur DOHS
Figure 5.7 Liquefaction potential vs depth (a) Chinese criterion and 125(b) Japanese code at Kholamura, Keraniganj
Figure 5.8 Critical N-value vs fines content 127
•
xiv
Gs
Yr"{wet
Ydry
LL
PLPI
FeDsoDIO
Cu
Dr
Z
g
M
HzPL
(Nl)60
FLFM
N
ER
L'..N1
R
amax
Natural moisture content
Specific gravity
Field density
Wet density
Dry density
Liquid limit
Plastic limit
Plasticity index
Fines content (% passing sieve # 200)
Mean grain size
Effective grain size
Uniformity coefficient
Relative density
Basic seismic coefficient
Gravity acceleration
Earthquake magnitude
Frequency
Liquefaction potential index
Corrected N-value for 60 % energy
Liquefaction potential
Fineness modulus
Field SPT N-value
Energy ratio
Increment ofN-value as a function of fines
content
Cyclic strength resistance
Peak horizontal acceleration on the ground
surface
Stress reduction coefficient
Depth
Length correction factor
xv
NOTATIONS
'Ydmax
Ydmin
GIGo
y
h
G
Er
'tmax
I
Ms
R
P
ho
Di
Sampler correction factor
Bore hole correction factor
Dynamic efficiency
Velocity energy ratio
Maximum laboratory density
Minimum laboratory density
Shear modulus ratio
Shear strain
Damping
Shear modulus
Poisons ratio
Shear wave velocity
Primary wave velocity
Unconfined compressive stress
Modulus of elasticity
Failure strain
Amplitude of average shear stress
Amplitude of maximum shear stress
Effective overburden pressure
Total vertical pressure
Energy efficiency
Corrected N-value
Energy efficiency assumed in the guideline
Correction factor for SPT N-value in terms of
confining pressure
Intensity
Surface-wave magnitude
Hypocentral distance
Probability
Mean focal depth
Mean epicentral radius
XVI
Chapter One
INTRODUCTION
1.1 GENERAL
If a saturated sand is subjected to ground vibrations, it tends to compact and
decrease in volume; if drainage is unable to occur, the tendency to decrease in
volume results in an increase in pore water pressure. If the pore water pressure
builds up to the point at which it is equal to the overburden pressure, the effective
stress becomes zero. At this condition, the sand loses its strength completely and it
develops a liquefied state. Ground failures generated by liquefaction had been a
major cause of damage during past earthquakes e.g., 1964 Niigata, 1968 Tokachi-
oki, 1971 San Frnando, .1976 Guatemala, 1989 Loma,Prieta and 1990 Philipinesf
earthquakes. Liquefaction phenomena can affect buildings, bridges, buried
pipelines and other' constructed facilities in many different ways.
Dhaka, the largest city and at the same time the capital of Bangladesh, enjoys a
distinct primacy in the national and regional urban hierarchy. Its central location,
comparative advantage of size and topography, and its administrative and other
functional importance have caused a rapid growth of the city's population
particularly during the last few decades. Dhaka has experienced an extremely
rapid population growth after the independence of Bangladesh _ from only 1.6
million in 1974 to about 10.0 million in 2001. The forecast of DMDP (1995)
anticipates a doubling of population over 25 years and an average annual growth
rate of 3.1%. High population increase demands rapid expansion of the city. But
unfortunately most of the lands have already been occupied. As a result, different
new areas are being reclaimed by both government and private agencies in and
around Dhaka city. In general, the practice for developing the new areas in Dhaka
city is just to fill lowlands by dredging material, which is almost silty sand. Loose
fills, such as those placed without compaction, are very likely to be susceptible toliquefaction.
C\
The historical seismicity data of Bangladesh and adjoining areas indicates that
Bangladesh is at seismic risk. Dhaka metropolis together with its surroundings is
situated in the seismic Zone 2 in the seismic zonation map of Bangladesh, which
has a basic seismic coefficient Z= 0.15 g (BNEC, 1993 and Sharfuddin, 200 I).
Therefore, the liquefaction potential of the reclaimed areas should be checked.
Although a few studies (Ansary and Rashid, 2000; Rashid 2000; Sabri, 2002;
Islam and Ahamed 2005; Islam, 2005) have been undertaken to establish
liquefaction possibilities at local levels in Bangladesh, no such research has been
conducted for determining the liquefaction susceptibilities of reclaimed areas of
the cities. To determine the liquefaction potential sub-soil characteristics of the
area in question should be determined. Although few researches have been
conducted to determine the geotechnical characteristics of Dhaka clay (Ameen,
1985), strength and deformation anisotropy of clays (Islam, 1999) and
compressibility and shear strength of remolded Dhaka clay (Uddin, 1990), no such
researches have been conducted to determine the sub-soil characteristics of
reclaimed areas of Dhaka city.
In the absence of a definite knowledge of sub-soil characteristics and liquefaction
possibilities at various localities, difficulties arise in finalizing design of many
important structures. It has been, therefore, felt necessary to undertake a study to
determine sub-soil characteristics and the liquefaction potential of the reclaimed
areas of Dhaka city. This study deals with the development procedure of
reclaimed areas, characteristics of fill materials, sub-soil characteristics and
liquefaction potential of selected reclaimed areas.
1.2 SEISMICITY OF BANGLADESH
Bangladesh covers one of the largest deltas and one of the thickest sedimentary
basins in the world. According to Bolt (1987) considering geology and tectonic of
Bangladesh and neighborhood five tectonic blocks can be identified which have
been in producing damaging earthquakes. These are:
i) Bogra fault zone
2
ii) Tripura fault zone
iii) Sub-Dauki fault zone
iv) Shillong plateau and
v) Assam fault zone
Considering fault length, fault characteristics, earthquake records etc., the
maximum magnitude of earthquakes that can be produced in different tectonic
blocks are given in Table 1.1 (Bolt, 1987).
Table 1.1 Maximum earthquake magnitude III different tectonic blocks (Bolt,
1987)
Tectonic blocks MagnitudeBogra fault zone 7.0
Tripura fault zone 7.0Sub-Dauki fault zone 7.3
Shillong plateau 7.0Assam fault zone 8.5
Information of earthquakes in and around Bangladesh is available for the last 250
years. Among these, during the last 150 years, seven major earthquakes have
affected Bangladesh. The surface-wave magnitude, maximum intensity according
to European Macroseismic Scale (EMS) and epicentral distance from Dhaka has
been presented in Table 1.2. Surface wave magnitudes and maximum intensity
(EMS) of the earthquakes are presented in Table 1.2 are according to the study of
Sabri (2002). The macroseismic information retrieved from all the sources had
been carefully analyzed and then used in the estimation of how the shock was felt
and how much damage was caused to man-made structures and to nature in many
locations based on the Oldham Scale of Intensity, The Rossi-Forel Scale and the
Modified Mercalli Intensity Scale. Details of the scales are presented at Appendix
-A. From Table 1.2, it is seen that the distance of epicenter from Dhaka city range
from 150 km to 500 km in most cases. The magnitude of the earthquakes
presented in the Table 1.2 is at the epicenter. The intensity of the earthquakes at
Dhaka can be determined by proper attenuation law such as provided in Equation
1.1.
3
4
Table 1.2 List of major earthquakes affecting Bangladesh during last 150 years(Ms ~ 7) (Sabri, 2002)
\
(1.1)I=5.602+1.546(Ms)-0.00121(R)-4.501(log R):t 0.82 P
where, I is intensity at any point, Ms is surface-wave magnitude, R is the
hypocentral distance that correspondence to the mean epicentral radius
D; = (R? - h/)1/2, P is probability and ho is the mean focal depth.
The seismicity zones and the zone coefficients may be determined from the
earthquake magnitude for various return periods and the acceleration attention
relationship. It is required that for design or ordinary structures, seismic ground
motion having 10% probability of being exceeded in design life of a structure (50
years) is considered critical. An earthquake having 200 years return period
originating in Sub-Dauki zone have epicentral acceleration of more than 1.0g but
at 50 kilometer the acceleration shall be reduced to as low as 0.3g. The
magnitudes of the earthquakes presented in the Table 1.2 was determined based
on estimation of the earthquake damages and hazards. Because that time
earthquake magnitude determination devices were not available. So, the
magnitudes presented may not be exactly correct. Figure 1.1 shows the epicenters
of historical earthquakes in and around Bangladesh.
Date Name of Earthquake Surface- Maximum Epicentral Basiswave Intensity distance from
magnitude (EMS) Dhaka (km)(Ms)
10 January, 1869 Cachar Earthquake 7.5 IX 250 Back calculatedfrom intensity
.14 July, 1885 Bengal Earthquake 7.0 VIll to IX 170
12 June, 1897 Great Indian Earthquake 8.7 X 230 Directly fromseismograph
8July,1918 Srimongal Earthquake 7.0 VIll-IX 150
2 July, 1930 Dhubri Earthquake 7.1 IX 250
15 January, 1934 Bihar-Nepal Earthquake 8.3 X 510
15 August, 1950 Assam Earthquake 8.5 X 780
Figure 1.1 Seismic map showing epicenters of historical earthquakes in andaround Bangladesh (Khan, 2004).
* *
*J* ****
*t*
+
+
+
*+*
**
),"*
*~* *""*",1{fI< * ** oj
*}i.,t*j. *** ~
84 86 88 90 92 94 96 98
*+* /"** + ** ~ .•••.**
*
*
+*
*
5
¥ 3 to* 4 to+ 5 toA 6 to
80 82
Some recent earthquakes in Bangladesh
• May 8, 1997 Sylhet earthquake (body wave magnitude, Mb = 5.6) which
had its epicentre in north-east Sylhet, near Jaintiapur (24.89°N, 92.25°E)
and led to cracking of a number of buildings in and around Sylhet (e.g.
Sylhet airport building, college near Jaintiapur, Grameen Bank building in
Barlekha).
• November 21, 1997 Bandarban earthquake (Mb = 6.0), which had its
epicentre near Bangladesh-Myanmar border (22.23°N, 92.74°E). A
number of buildings in the Chittagong region were damaged.
• July 22, 1999 Moheshkhali earthquake (Mb =5.1) had its epicentre near
Moheshkhali island (21.47°N, 91.900E). A number of mud-wall houses
collapsed and cracks were formed in some pucca buildings. Six people
were killed.
• July 27, 2003 Barkal earthquake had its epicenter near Barkal. The
intensity of the earthquake took everyone by surprise due to its strong
shaking and widespread damage. The hypo centre of the earthquake was
estimated by United States Geological Society Survey to be at 22.82°N,
92.32°E with a focal depth of 10 km. The magnitude of the main shock
was 5.6 on moment magnitude scale (5.5 in the surface-wave scale). Many
after shocks of smaller intensity occurred in the same area on the same day
and on the following days. Due to poor construction practice and low
strength of the mud houses a lot of damage was occurred. About five
hundred 500 families became homeless. One hundred and fifty houses
were collapsed due to this earthquake. One person was died due to panic.
Some buildings were also damaged.
• September 18, 2005, an earthquake of magnitude 5.8 was felt in Dhaka.
The distance of epicenter of the earthquake was around 460 km to the east
of Dhaka.
6 ,
1.3 LIQUEFACTION AND ITS SIGNIFICANCE
If saturated sand is subjected to ground vibrations, it tends to compact and
decrease in volume; if drainage is unable to occur/prevented, the tendency to
decrease in volume results in an increase in pore water pressure, and if the pore
water pressure builds up to the point at which it is equal to the overburden
pressure, the effective stress becomes zero, the sand loses its strength completely,
and it develops a liquefied state.
The liquefaction problem has been attracting engineering concern for about past
25 years. It was not considered important before, although large earthquakes had
caused liquefaction in loose sand deposits. This seems so because cities in old
times were not too large and were confined within areas of stable deposits,
reclaimed land was rare, and attention was paid mostly to such seismic effects as
collapse and burning of buildings. The liquefaction problem became important for
the first time when it started to affect human and social activities by disturbing the
function of facilities. The loss offunction is exemplified as:
a) Subsidence of road embankments which leads to cracking m
surface pavements and block traffic.
b) Building subsidence and tilting to such an extent that its normal use
is not possible.
c) Lateral movement of bridge abutments and piers, as well as, in the
most extreme cases, collapse of a bridge.
d) Breakage and separation of buried pipes, which take supply of
water and gas out of service.
e) Floating of sewerage treatment tanks and buried pipes, which make
normal flow of water impossible.
Liquefaction phenomena can affect buildings, bridges, buried pipelines and other
constructed facilities in many different ways. Liquefaction can also influence the
nature of ground surface motions. Flow liquefaction can produce massive flow
slides and contribute to the sinking or tilting of heavy structures, the floating of
7
light buried structures, and to the failure of retaining structures. Cyclic mobility
can cause slumping of slopes, settlement of buildings, lateral spreading and
retaining wall failure. Substantial ground oscillation, ground surface settlement,
sand boils and post earthquake stability failures can develop at level ground sites.
1.4 STUDY BACKGROUND
The followings are the background of the present research.
a) The low incidence of severe earthquakes during the last hundred
years has led to a situation where most of the population and the
policy-makers do not perceive seismic risks to be important. But
the historical seismicity data of Bangladesh and adjoining areas
indicates that the capital city Dhaka is at high seismic risk.
b) The present population and the population density of the Dhaka
city anticipate a doubling of population over 25 years. High
population increase demands rapid expansion of Dhaka City. As a
result, different new areas are being reclaimed in and around
Dhaka city by both government and private agencies.
c) The practice for developing the new areas is just to fill lowlands
by dredged materials, which is almost silty sand. Loose fills, such
as those placed without any compaction, are very likely to be
susceptible to liquefaction.
Although a few studies have been conducted to establish liquefaction possibilities
at local levels in Bangladesh, no such research has been conducted for
determining the sub-soil characteristics and liquefaction potential of reclaimed
areas of cities.
1.5 SCOPES AND OBJECTIVES
Based on the above mentioned background the major objectives of this research
are as follows.
8
a) To identify reclaimed areas within Dhaka city and to obtain
information relating to procedure followed for reclaiming these
areas.
b) To characterize the sub-soil of selected reclaimed sites of Dhaka
city by both field and laboratory tests.
c) To determine the liquefaction potential of the reclaimed areas
based on the standard penetration test (SPT) and laboratory test
results.
d) To develop a rational for effective reclamation procedure that may
reduce liability for liquefaction.
It is expected that the results obtained from the research can be used for
foundation" design considerations of the reclaimed areas of Dhaka city. The
research would enable to identify vulnerable areas. It is also expected to provide
suggestions for appropriate ground improvement or other methods to overcome
the liquefaction problem of the vulnerable areas. The project will delineate
vulnerable areas within the reclaimed areas of the Dhaka city providing a public
awareness of the earthquake hazards within these areas. It is also expected that
this research would provide selections to prevent or taken liquefaction related
problems in these areas for safe living. This will add to the prevalent stock of
knowledge of civil engineers engaged in infrastructure building in liquefaction
vulnerable areas in Bangladesh. These maps will be useful for preliminary
selection of a project site, land use planning, zoning ordinances, pre-disaster
planning, capital investment planning etc.
1.6 THE RESEARCH SCHEME
Several laboratory tests are in practice to estimate the liquefaction potential of
soils such as cyclic triaxial test, cyclic simple shear test and shaking table test.
Similarly, several in-situ empirical criteria have been developed over the years
based on standard penetration test (SPT), cone penetration test (CPT) and shear
wave velocity measurement for the assessment of liquefaction potential (Seed and
Idriss, 1971; Seed and Idriss, 1982, Seed et aI., 1985; Iwasaki et aI., 1982; Seed
9
and Peacock, 1971; Youd and Idriss, 2001; Robertson and Campanella, 1985).
However, in this study liquefaction potential of selected reclaimed sites have been
determined from standard penetration test (SPT) and laboratory test results based
on Seed and Idriss (1982), Japanese Code of Bridge Design (Tatsuoka, et. aI.,
1980) and Chinese Criterion (Ishihara, 1990).
The whole research has been conducted according to the following phases:
i) Field survey has been conducted to identify and locate the
reclaimed areas of Dhaka city. In this .survey, development
procedure (i.e., materials used for filling, filling procedure,
equipment used for filling, compaction) of the reclaimed areas has
also been examined.
ii) Sub-soil data of selected reclaimed areas of Dhaka city has been
collected from different sub-soil investigation compames,
government, semi-government and non- government organizations.
iii) Field investigation that includes 16 (Sixteen) boreholes at different
locations of selected reclaimed areas has been conducted. During
drilling, SPT has been taken at 1.5 m intervals and disturbed and
undisturbed samples have been collected.
iv) Extensive laboratory investigations that will include specific
gravity test, grain size analysis, Atterberg limits, laboratory density
test and unconfined compression test has been conducted on the
collected samples collected from various depths of each boring.
v) Sub-soil profile of the reclaimed areas has been determined based
on the test results.
vi) Using the sub-soil data, extensive computation has been performed
using high precision computers based on the methods (Seed and
Idriss, 1982; Japanese Code of Bridge Design and Chinese
Criterion) mentioned above to evaluate whether the soil is
liquefiable or not and ifliquefiable, to what extent.
10
vii) Accumulating these results obtained for various depths and
locations, liquefaction maps for the site may be developed.
However, in this study such maps have not been developed.
1.7 OVERVIEW OF RESEARCH PROGRAM
The major focus of this research is to determine sub-soil characteristics and the
liquefaction potential of the reclaimed areas of Dhaka city. The research can be
divided into three parts:
a) To study the development procedure of the reclaimed areas
b) Determination of sub-soil characteristics from field and laboratory
tests
c) Determination of liquefaction potential using different methods
Chapter 2 is devoted to the review of past researches in Bangladesh and other
parts of the World. Development of seismic zoning map of Bangladesh and
seismic zone coefficients has also been presented in this chapter. Damages due to
liquefaction and countermeasures against liquefaction are also discussed in this
chapter. Methods for liquefaction potential analysis and suitable methods are
described in this chapter. Details of the methods - Japanese code of bridge design
(Tatsuoka et. aI., 1980) and Chinese Criterion (Ishihara, 1990) have been
presented in this chapter.
Chapter 3 deals with the development procedure of reclaimed areas. Selections
of source material, characteristics of filling materials, filling methods, are
described in this chapter. Based on the reclamation procedure, a rational method
has been proposed for the reclaimed areas to avoid liquefaction.
Chapter 4 describes the test programme and brief description of the test methods.
Field and laboratory test results have been described in Chapter 4. Field test
results such as field density test, standard penetration test (SPT) and laboratory
test results such as specific gravity, grain size, Atterberg limit, moisture content
and unconfined compression tests are described in this chapter. Sub-soil
11
characteristics of the selected reclaimed areas based on the field investigations and
collected data have been presented in this chapter.
Liquefaction potential determination has been discussed in Chapter 5. Preliminary
estimation of liquefaction potential of selected reclaimed areas has based on
geomorphological condition, soil characteristics, SPT N-value and past earthquake
case studies has been presented. Liquefaction potential based on Japanese code of
bridge design and Chinese Criterion has also been presented in this chapter.
The final chapter, Chapter 6 is a summary of the reclamation procedure, material
Characteristics, sub-soil characteristics and liquefaction potential. This chapter
also includes scopes for future researches.
12 •
Chapter Two
LITERATURE REVIEW
2.1 GENERAL
The objective of this chapter is to review the available literature critically related to
liquefaction. This chapter deals with the past researches that were related to
evaluation of liquefaction potential, liquefaction zone, measures against liquefaction
in Bangladesh and other parts of the world. Classification of liquefaction induced
damages and measures against liquefaction have also been discussed in this chapter.
Prediction, susceptibility and determination of liquefaction have also been presented
in this Chapter.
2.2 PAST RESEARCHES RELATED TO LIQUEFACTION
A Few researches have been conducted to determine the liquefaction potential in
local levels of Bangladesh. Many researches have been conducted concerning
liquefaction in different parts of the world as many earthquakes caused damages due
to liquefaction. Major researches conducted in local level of Bangladesh and other
parts of the World have been presented below briefly.
Seed and Idriss (1971) presented test procedures for measuring soil liquefaction
characteristics.
Youd and Perkins (1978) developed a procedure for using geologic and seismologic
information in compiling maps showing liquefaction induced ground failure
potentia!. The procedure requires the superposition of two constituent maps: (I) a
ground failure opportunity map and (2) a ground failure susceptibility map.
Procedures for compiling these maps have also been developed.
Davis and Berrill (1981) provided assessment procedure for liquefaction potential
based on seismic energy dissipation.
13
14
Seed and Idriss (1982) made an attempt to summarize as simple way as possible, the
essential elements of current state art of evaluating liquefaction or cyclic mobility
potential of soil deposits on level ground.
< 15 %
<35 %
> 0.9 LL
Clay content (defined as % finer than 0.005 mm):
Liquid limit (LL):
Water content (Wn):
where, LL is liquid limit
Seed and Idriss (1983) outlined criteria, derived from case histories in China (Wang,
1979), which provided a basis for partitioning clayey soils vulnerable to sever
strength loss as a result of earthquake shaking. The clayey soils vulnerable to sever
strength loss appeared to have the following characteristics:
Seed et at (1983) evaluated liquefaction potential using field test data. They used
simplified procedure for evaluating the liquefaction potential of sand deposits using
data obtained from Standard Penetration Test (SPT). Field data for sites which were
known to be liquefied or not liquefied during earthquakes in the United States, Japan,
China, Guatemala, Argentina and other courtiers were presented to establish a
criterion for evaluating the liquefaction potential of sands in Magnitude 7.5
earthquakes. The results of this study were then extended to other magnitude
earthquakes using a combination of laboratory and field tests data. Available
information on the liquefaction resistance of silty sands was also reviewed and a
simple procedure for considering the influence of silt content was proposed. A
method was presented for using the field tests data to evaluate the possible
magnitude of pore water pressure generation in sands and silty sands which remain
stable during earthquake shaking. Finally, the applicability of other in situ field tests,
such as the static cone penetrometer, shear wave velocity and electrical
measurements for evaluating the liquefaction resistance of soils was examined.
Because the empirical approach was founded on such a large body of field data, it
was believed by the authors to provide the most useful empirical approach available
at the present time. However, it had been noted that the standard penetration test
cannot be performed conveniently at all depths (say deeper than 30.5 m or through
large depths of water) or in all soils (such as those containing a significant proportion
of gravel particles). Thus, it was desirable that it was being supplemented by other in
situ test methods which can also be correlated with soil liquefaction potential. In
many cases, the static cone test, which can be performed more rapidly and more
continuously, may provide a good means for evaluating liquefaction potential,
especially if it was correlated on a site dependent basis with SPT results. However,
this procedure was limited also to sands and silty sands. In dealing with soils
containing large particle, or in difficult environments, other in situ characteristics,
such as the shear wave velocity or the electrical characteristics of the soil may
provide a more suitable means for assessment of liquefaction potential. And, in due
course, any or all of these in situ test methods may have their own detailed
correlation with field performance to validate their usefulness as meaningful
indicators of liquefaction characteristics. It seems likely, however, that for onshore
sites and with deposits of sand up to 30.5 m deep or so, the correlation of
liquefaction characteristics with Standard Penetration Test data will provide the most
direct empirical means of evaluating field liquefaction potential for some years to
come. Other methods, however, have a significant role to play and should be
developed to the fullest extent possible to provide information for different soil types
and environments.
Seed et al. (1985) described the influence of SPT procedures in soil liquefaction
evaluations.
Samson et al. (1988) developed regression models to evaluate liquefaction
probability. Statistical models were developed to express the probability of
liquefaction as a function of earthquake load and soil resistance parameters. Results
were obtained based on a catalog compiled for the study, which consists of 278 cases
of liquefaction/non-liquefaction occurrences. A method of binary regression was
used to derive four models recommended for use in assessment of liquefaction
probability. Two of them use the cyclic stress ratio (Seed and Idriss, 1971) as the
earthquake load parameter; the other of two use, as load parameters, explicit
functions of earthquake magnitude and distance, similar to the function proposed by
15
Davis and Berrill (1981). All four models measure liquefaction resistance through
the corrected/normalized SPT (N 1)60 value. Recommendations for practical
implementation were provided and comparisons were made with other methods of
liquefaction analysis. A statistical regression procedure had been used to derive
models for calculating the probability of liquefaction as a function of earthquake of
liquefaction as a function of earthquake load and soil resistance parameters. The
effects of soil gradation variables (such as fines content, gravel content and median
grain size) on the liquefaction probability had been studied. In most regressions
involving these variables, the accuracy of parameter estimation is limited by missing
or incomplete data, so that only qualitative trends could be discerned. Of the various
gradation effects, only that of fines content was considered to be adequately
supported by the current data to warrant recommending its use in risk analysis. In
applications such as regional mapping of liquefaction risk, obtaining detailed
information on soil gradation may not be worthwhile. Because of limitations of the
data base, the regression models give conservative estimates of the probability of
liquefaction.
Kramer and Seed (1988) described initiation of soil liquefaction under static loading
conditions. Liquefaction of loose, saturated sands may be caused by cyclic or static
(monotonically increasing) undrained loading. Most previous studies of static
liquefaction behavior had emphasized liquefaction susceptibility and the behavior of
liquefied soils. An experimental investigation was undertaken to evaluate the stress
conditions required to initiate liquefaction and the influence of various parameters on
those stress conditions. The static liquefaction resistance, defined as the shear stress
increase under undrained conditions required to initiate liquefaction, was observed to
increase with increasing relative density and confining pressure, and to decrease
dramatically with increasing initial shear stress level. At high initial shear stress
levels, initiation of liquefaction was observed to result from increases in shear stress
under undrained conditions of only a few percent of the initial shear stress. The
distinction between the initiation and the effects of liquefaction was discussed, and
an expression for a factor of safety against the initiation of liquefaction was
proposed.
16
Rashid (2000) developed seismic microzonation map of Dhaka City based on site
amplification and liquefaction. Local site conditions and liquefaction potential of
sites were used for microzonation of Dhaka city. Dhaka was first divided into small
grids. At the grid points shear wave velocities were estimated by using SPT test
results. More than two hundreds borehole data were collected and converted into
shear wave velocities using empirical relations. All these data were used to estimate
vibration characteristics at different grid points of the city employing one
dimensional wave propagation program SHAKE. The computations were made in
the frequency range of 0 to 20 Hz. The loss of energy of seismic waves in the soil
layers was also considered. In the. study, at each site of Dhaka city, .liquefaction
potential was analyzed using maximum acceleration of 150 cm/s2• This maximum
acceleration was based on 200 years peak ground surface acceleration contour
estimated from earthquake hazard analysis for Bangladesh based on National
Oceanic and Atmospheric Administration earthquake data from 1900 to 1977. The
liquefaction potential of different locations of Dhaka was estimated by two methods:
Seed et al. (1983) where SPT data was used and Iwasaki et al. method (1982) based
on topographical information. The results of the amplification and liquefaction
analysis were transformed into microzonation maps depicting: (i) zones showing
quantitative estimates of site amplification; (ii) zones showing the natural frequency
of the soils; (iii) zone showing qualitative estimates of liquefaction potential; (iv)
zones showing quantitative estimates of liquefaction potential.
Andrews and Martin (2000) presented criteria for liquefaction of silty soils. They
showed that if the clay (0.002 mm) content is less than 10% and liquid limit is less
than 32, the soil is susceptible to liquefaction. Again, if the liquid limit ~ 32 then the
soil may be liquefied. If the clay content ~ 10% and liquid limit <32 the soil may
liquefy, but if the liquid limit> 32 the soil is not susceptible to liquefaction.
Sabri (2002) estimated earthquake intensity- attenuation relationship for Bangladesh
and its surrounding region. This study presented the results of an investigation of the
magnitude-intensity and intensity-attenuation relationships for earthquake in
Bangladesh and its surrounding region using available macroseismic data. The
results of this study show that the intensity-attenuation models were adequate to
17
predict quite well the die-out of intensity with distance for Bangladesh and its
surrounding region; it was also found that magnitude could be predicted accurately
by calibrating isoseismal radii against instrumental surface- wave magnitude. Such
magnitude-intensity relationships might be used to evaluate the magnitude of
historical earthquakes in the region under survey, with no instrumental data, for
which isoseismal radii and intensities were available.
Hossain et aI. (2003) evaluated sub-soil characteristics and liquefaction potential of
Mirpur DOHS area. To characterize soil deposit eight bore holes were drilled at the
project site. Moisture content, specific gravity, Atterberg limits, grain size
distribution, unconfined compressive strength, density and shear strength parameters
of the collected samples were determined in the laboratory. It was observed that
geotechnical properties of the soil in the study area varied with depth and location. It
was observed that loose soil exits from 4.7 to 14.0 m depth below existing ground
level (EGL). From the study, the possibility of the liquefaction was found to be zero.
However, more detailed study have been conducted in these study of these area
based on these data and other data collected from different agencies
Rao (2003) evaluated the liquefaction potential for seismic microzonation of Delhi
region. The Bhuj earthquake on 26th January had resulted in heavy losses to several
places/cities such as Bhuj, Anjar, Bachau and far off places like Ahamedabad and
Sural. Delhi and surrounding regions had been classified under zone IV having high
seismic probability. Keeping this in view microzonation of Delhi had been taken up
in the study. Extensive geological, geotechnical and seismological investigations had
been conducted to estimate the liquefaction potential of Delhi region to mitigate
seismic hazard. Liquefaction potential evaluation from the Standard Penetration Test
(SPT) data was presented. Preliminary liquefaction studies for Delhi region indicated
that the south-east blocks, north-east parts of Alipur and the whole of Shahdara block
fall into risk category. There was a high possibility of liquefaction occurring towards
the North Campus (Model Town), Old Delhi areas and around CP and east of the
Yamuna i.e. Gazipur and Shakapur. Considerable potential also exists in the areas
such as Motinagar, Siri Fort and Kalindi Kunj.
18;-"~ ...
•
Islam and Ahamed (2005) conducted preliminary evaluation of liquefaction potential
of selected reclaimed areas of Dhaka City. It was observed that some parts of the
reclaimed areas are susceptible to liquefaction and some parts are not liquefiable.
Islam (2005) estimated the seismic losses for Sylhet City for scenario earthquakes.
Liquefaction potential index (PL) had been determined for the city. It was found that,
3.35 Km2 area has low and very low liquefaction potential, 13.70 Km2 areas have
high liquefaction potential. More than one thirds (37%) area will be affected severely
due to liquefaction if Srimongal Earthquake (1918) occurs again with same
magnitude and same epicentral distance.
Madabhushi (2005) has swnmarized ground improvement methods for liquefaction
remediation. These include in-situ densification, provision of drainage using stone
colwnns or specialist geo-drains, strengthening the loose sandy soils by grout
injection. The relative success of these ground improvement methods in preventing
damage after a liquefaction event and the mechanisms by which they can mitigate
liquefaction continue to be areas of active research. The use of dynamic centrifuge
modeling as a tool to investigate the effectiveness of ground improvement methods
in mitigating liquefaction risk had been presented. Three different ground
improvement methods had been Considered. Firstly, the effectiveness of in-situ
densification as a liquefaction resistance measure had been investigated. It was
shown that mechanism by which the soil densification offers mitigation of
liquefaction risk can be studied at a fundamental level using dynamic centrifuge
modeling. Secondly, the use of drains to relieve excess pore pressures generated
during an earthquake event will be considered. It will be shown that the current
design methods can be further improved by incorporating the understanding obtained
from dynamic centrifuge tests. Finally, the use of grouting of soil to mitigate
liquefaction risk will be investigated. It will be shown that by grouting the
foundation soil the settlement of a building can be reduced following earthquake
loading. However, the grouting depth must extend the whole depth of liquefiable
layer to achieve this reduction in settlements.
19
2.3 SEISMIC ZONING MAP OF BANGLADESH
The seismicity zones and the zone coefficients may be determined from the
earthquake magnitude for various return periods and the acceleration attention
relationship. It is required that for design or ordinary structures, seismic ground
motion having 10% probability of being exceeded in design life of a structure (50
years) is considered critical. An earthquake having 200 years return period
originating in Sub-Dauki zone have epicentral acceleration of more than 1.0g but at
50 kilometer the acceleration shall be reduced to as low as O.3g.
Ali (1998) presented the earthquake base and seismic zoning map of Bangladesh.
Tectonic frame work of Bangladesh and adjoining areas indicate that Bangladesh is
situated adjacent to the plate margins of India and Eurasia where devastating
earthquakes have occurred in the past. Non-availability of earthquake, geologic and
tectonic data posed great problem in earthquake hazard mapping of Bangladesh in
the past. The first seismic map which was prepared in 1979 was developed
considering only the epicentral location of past earthquakes and isoseismal map of
very few of them. During preparation of National Building Code of Bangladesh in
1993, substantial effort was given in revising the existing seismic zoning map using
geophysical and tectonic data, earthquake data, ground motion attenuation data and
strong motion data available from within as well as outside of the country.
Geophysical and tectonic data were available from Geological Survey of
Bangladesh. Earthquake data were collected from NOAA data files and Geodetic
Survey, U.S. Dept. of Commerce.
Seismic zoning map for Bangladesh has been presented in Bangladesh National
Building Code (BNBC) published in 1993. The pattern of ground surface
acceleration contours having 200 year return period from the basis of this seismic
zoning map. There are three zones in the map - Zone 1, Zone 2 and Zone 3. The
seismic coefficients of the zones are 0.075g, 0.15g and 0.25g for Zone 1, Zone 2 and
Zone 3, respectively. Bangladesh National Building Code (1993) placed Dhaka City
area in Seismic Zone 2 as shown in Figure 2.1. The seismic zones in the code are not
based on the analytical assessment of seismic hazard and are mainly based on the
20
location of historical data. An updated seismic zoning map as shown in Figure 2.2
based on analytical studies was recently developed by Sharfuddin, (2001). This
zoning was based on consistent ground motion criterion such as equal peak ground
acceleration levels. In this map also Dhaka City has been placed Zone 2. This map
also has been three zones namely - Zone 1, Zone 2 and Zone 3. The seismic
coefficients are also the same as in the map presented by BNBC (1993). The only
modifications are is the zone areas. From both maps, it is seen that Dhaka city
belongs to Zone 2 where the seismic coefficient is 0.15g.
2.4 CASE STUDIES
There are many earthquakes III the past where liquefaction occurred. A lot of
dainages occurred due to those past earthquakes. Among these a few have been
described below:
Kocaeli Earthquake, 1999
Damages due to liquefaction were observed in major earthquake such those in 1999
in Greece, Taiwan and Turkey (Madabhushi, 2005). For example, in Turkey the
Adapazari area suffered extensive liquefaction. The soil investigation in this area had
revealed the typical low SPT values that establish the vulnerability of the soil to
liquefaction during strong earthquake events. In Figure 2.3, the borehole data from
Adapazari was presented. It is seen from this figure that the soil layers up to a depth
of 10m have low SPT values (i.e., N<IO) and were either silt or silty sands. The
water table existed at a depth of about 2.1 m below ground surface. These conditions
made this site vulnerable to liquefaction and the area suffered severe liquefaction
induced damage during the 1999 Kocaeli earthquake.
21
••••,."-\
I H D I A
)CI ~ IIWl 110 ~ •••, , ! 1
sou:
"."
IN D I A
nAY OF D!NQAL
22
1II~_ 1IN'Ie.'J _
~ "Ito ••
Figure 2.1 Seismic zoning map of Bangladesh (BNBC, 1993).
.'~'l ••" ~ •..•. - - lZlE3~a.-.t1:ClI,I'~__ ~ r
23
Figure 2.2 Seismic zoning map of Bangladesh (Sharfuddin, 2001).
Seismic Zones_ Zone 3 ;;;:0.25g
_ Zone 2'" 0.15g_ Zone 1 = 0.075g
24
504030
Silt-sand
2010oo
Uncorrected SPT Blow Counts, N30
Niigata Earthquake, 1964
Figure 2.3 Borehole data from Adapazari in Turkey (Madabhushi, 2005)
Although the epicenter of the Niigata earthquake (Magnitude= 7.5) was located
about 35 miles from Niigata and the maximum ground accelerations recorded in the
city were about 0.16g, the earthquake induced extensive liquefaction in the low lying
areas of the city. Water began to flow out of cracks and boils during and immediately
following the earthquake, causing liquefaction of the deposits widespread damage.
Many structures settled more than 3 ft. in the liquefied soil and the settlement was
often accompanied by severe tilting. Thousands of building collapsed or suffered soil
damage as a result of these effects.
The city is underlain by a deep deposit of sand with a 50 percent size about 0.2 to 0.4
mm and a uniformity coefficient of about 10. Following the earthquake an extensive
survey of the distribution of the damaged structures was made. It was found that
structure in the coastal dune area (designated Zone A) suffered practically no
damage. The major damage and evidence of liquefaction were concentrated in the
low land areas but even here, two distinct zones could be clearly recognized- one iIi
which damage and liquefaction were extensive (Zone C) and one in which damage
was relatively light (Zone B). Because all zones contain similar types of structures,
the differences in extent of damage could be attributed to differences in the subsoil
and foundation behavior.
The difference in behavior in zone A from that in zone B and zone C could be
readily is attributed to two major differences in soil characteristics. Although all
zones are underlain by sandy soils to a depth of approximately 100 ft., in zone A
underlying sands were considerably denser than those zone B and zone C and
furthermore, the water table was at a much greater depth below the ground surface.
In zone Band C, however, the general topography and depth of water table was
essentially the same. It was therefore concluded that the difference in extent of
damage in these two zones must be related the characteristics of the underlying
sands.-
Because the soils involved in the sands, efforts were concentrated on the
determination of the relative density of the sand by means of standard penetration
tests. Koizumi (1966) has presented the results of a number of borings made in
Zones Band C to show the variation of penetration resistance with depth in the two
zones. There is a considerable scatter of the results in anyone zone, but averaging
the values obtained leads to the comparative values shown in Figure 2.4.
It may be seen that in zones Band C, the average penetration resistance of the sand
is essentially the same in the top IS ft. below this the sands in zone B are somewhat
denser that those in zone C. Below about 45 ft., the sands in both zones are relatively
dense and are unlikely to be involved in liquefaction. It seems reasonable to
conclude that the relatively small difference in penetration resistance in sands in the
25
26
PENETRATION RESISTANCE, PENETRATION RESISTANCE,N, blows/ft N, blows/ft
0 20 1,0 60 80 0 20 40 60 800 0 GWTGWT- ~
15 15\
~, ~ 3030 ',<,ZONE
~~ B. .:c :I:
t-t-
\ 0-0- 1,5 w 45w<:><:>
\60 \ 60\
\75 75(a) (b)
a) Loss of bearing capacity in foundation
b) Floating of buried structures
c) Dislocation of retaining walls
Figure 2.4 Standard penetration resistance ofNiigata sand (Seed and Idriss, 1982)
depth range from 15 ft. to 45 ft. are responsible for the major difference III
foundation and liquefaction behavior in the two zones.
Some damages due to liquefaction during past earthquakes have been presented in
Figure 2.5. Picture (a) and (b) in Figure 2.5 show the tilling of apartment building
and collapse of superstructure of bridge due to 1964 Niigata Earthquake. Pictures (a)
and (b) in Figure 2.5 show the fissure in a field and tilling of a school flag due to
1977 Caucete Earthquake and 1983 Nihon-Kai Chubu Earthquake, respectively.
From these pictures, it is clear that serene damage and collapse may occur to
structures, foundations and grounds due to liquefaction.
2.5 LIQUEFACTION - INDUCED DAMAGES
From the case studies described earlier and past earthquakes, it is seen that the
damages due to liquefaction can be classified as:
Tilting of a school flag pole due to
ground failure caused by
liquefaction during the 1983
Nihonkai-Chubu Earthquake
d) Lateral soil movement
e) Variation in natural period of ground
f) Dissipation of excess pore water pressure and associated
consolidation of sand
g) Ground distortion
Figure 2.5 Damages due to liquefaction during some past earthquakes.
27
a) Tilting apartment buildings at b) Collapse of the super- structure of
Kawagishi- Cho, Niigata, produced by the Showa Bridge by falling off its
liquefaction of the soil during the 1964 piers; 1964 Niigata Earthquake
Niigata Earthquake
~":f";it",',""'""': . /.1••..""'":::';"":- '~""::e
~~~~"~x. ., "--a'~~:C:""""-'"'~~" ';
-;;21i;~~~~~~;:tk':_c) Linear fissure in a soccer field III the d)
town of Caucete caused by the
liquefaction that occurred in the 1977
Caucete Earthquake
2.6 STRATIGRAPHY OF LIQUIFIABLE GROUND
The stratigraphy of liquefiable ground can be classified in to seven types as shown in
Figure 2.6 (JGS, 1998) such as Type I, 2 and 3 are the natural ground with a
horizontal surface, Type 4 and 5 are the natural ground with an inclined surface.
Type 6 and 7 are of man-made ground. Failure modes associated with in this type of
ground can be classified as follows.
Category A: Infinite horizontal ground (Type I and 2)
The ground in this category potentially induces the failure modes of structures
considered in the conventional approach. In type 2 the existence of non-liquefied
layer above the liquefied ground may reduce the degree of damage to structures
resting on it.
Category B: Horizontal ground offinite extent (Type 3)
In this category, significant relative displacement at the boundaries between liquefied
and non-liquefied zone will result in an additional failure mode. The relative
displacements include not only those during shaking but those after shaking .which
results in differential settlement.
Category C: Ground with inclined surface (Types 4 amI 5)
With an inclined surface, the liquefied ground will flow with or without limits and
this will result in an additional failure mode. With the lateral boundaries seen in type
5, the displacement of the ground surface may be reduced.
Category D: Soil structure and mall-made land (Type 6 and 7)
With free boundaries, liquefied soil will deform until its deformed geometry recovers
its equilibrium. With boundaries imposed' by structures such as in type 7, soil
structure interaction governs the deformation and the failure modes of the soil
structure systems.
28
Type 4
.> ,,~
" •• ',1 :~_.::>'~.,':' -,,..''-,."..~..l:fL~-;;efiedI:,
Type 7
Liquefied
Type 3
.,;.:;.
(. ') /.' irLiquefiedi?"' ;os, ••• ~. ,_,
h. .-:.:;~-::.;-',:".'i~1." . "',"
Type 6
Liquefied
XIWV\
Type 2
Type 5
'.,' . "-,
Liquefied
Type I
- a) To asses liquefaction potential
b) To evaluate the effects ofliquefaction
c) To determine effective remedial measures against liquefaction
d) To evaluate the effectiveness of the measures
29
Figurc 2.6 Classification of liquefiable ground types (JGS, 1998),
i .. ' I " ;
[ILiquefied I.!.; .. ,,'
2.7 REMEDIATION OF LIQUEFIABLE GROUND
There are two approaches for the remediation of liquefiable ground- Conventional
Approach and General Approach. These are described below:
2.7.1 Convcntional Approach
The objective of remediation of liquefiable ground is to reduce the effects of
liquefaction on buildings, transportation structures, and lifeline facilities, The steps
taken to achieve this objective are:
There are three basic failure modes of ground and soil structure due to liquefaction.
The understanding of these failure modes should be the basis of the best strategy for
the remediation of liquefiable ground. Remedial measures against liquefaction may
be classified into the following three categories.
a) To treat liquefiable soil
b) To strengthen structures or make them flexible to relieve the effects of
liquefaction
c) To prepare auxiliary facilities
The conventional approach for remediation of liquefiable ground is illustrated in
Figure 2.7 (JGS, 1998). If the liquefaction potential is high, then the strategy for
remediation is shown in area bounded by the double line shown in the figure. At
present the generalized approaches for assessment of failure methods and evaluation
of degree of damage have not been fully established and this fact is hence indicated
by the broken lines in the figure.
In the conventional approach, fundamental failure modes include:
a) Deformation of pile foundations due to reduction of horizontal soil
resistance,
b) Uplift of buried structures due to generation of buoyancy, and
c) Settlement of structures and slope failure due to reduction of shear
resistance of the soil.
The underlying assumption has been that ground is horizontally layered.
30
Principle ofRemediation
ChagcBoundary Shape
(Ground Improvement)
(Auxiliary Facility)
Principle ofRemediation
ChageDefonnaliOllCharacteristics
Possibility ofLlquefiction
Acceptability of NoDisplacement
Acceptability of NoDisplacement
No
31
Figure 2.7 Conventional approach for remediation of liquefiable ground (lGS, 1998)
2.7.2 Generalized Approach
Based on the detailed review of liquefaction-induced failure modes a generalized
approach to remediation against liquefaction may be suggested as shown in Figure
2.8 (lGS, 1998). In this approach, the assessment of liquefaction potential will be
done following the conventional approach. Then, the boundaries of the liquefiable
area will be evaluated. It is generally dependent on soil properties, intensity and
duration of shaking, and stratigraphy of the ground. The liquefied part of the ground
is regarded as behaving like liquid in order to identifY the governing failure modes of
a structure.
32
Selection of Remedial Principle(n) Soil Improvement(b) Structural ModificationCd) Combination
Idemi lication ofFailure Modes
Evaluation ofDegree of Damage
1
1
1
Assessment ofLiquefaction
J----1
~~/~SSibilitY 01''----.,_> ,...........~qUCfactlo:-./ _
~~.------I Yes
,---------,--. I IE-v-a-Iu-at-io~-o-f -I~_ Remedl~l Effect!
No
Figure 2.8 Generalized approach for remedial work (lGS, 1998).
C End-,'---~'
---..-------~-~~cccplabjJity 00,,--.., No ,~ Degree of Damage....-/..__r-
~"------/~'-- I-~c~ ,_==~~=~ _-i
a) High density
b) Appropriate grain size distribution for no liquefaction
c) Stable skeleton of soil particles
d) Low saturation
The next step is to evaluate the extent of damage to the structure. This evaluation
should be done with respect to the external as well as internal instability. For
example, pipeline system for sewage water may have been designed to be flexible
enough to absorb ground deformation to satisfy internal stability, but they may need
major remediation measures to meet the external stability requirement in order to
maintain their function to drain sewage water.
It might be said that the methodology to evaluate the extcnt of liqucfaction induced
damage has not been fully established, but there has been rapid developmcnt in this
field. Along this line the factor FL, which often plays a central role in conventional
practice, does not playa governing role in the present approach.
A factor of safety greater than one indicates that the liquefaction resistance exceeds
the earthquake loading, and thercforc that liquefaction would not bc expected.
2.8 MEASURES AGAINST LIQUEFACTION
There are several remedial measures against liquefaction. The choice of rcmedial
technique depends on soil type, seismicity of the area and importance of the structure
etc. The decision of ground improvement technique to be taken depends on some
criteria such as described in Tablc 2. I.
Table 2.1 Summary of the liquefaction potential index
Liquefaction Criteria Explanation
Probability
High IS < PL Ground improvcment is indispensable
Moderate S < PL::; IS Ground improvemcnt is required. Investigation
of important structures is indispensable
Low o <PL::;S Investigate of important structures is requiredVery low PL- 0 No measured is required
Choice of remedial teclmiques depends on:
a) Preventing the generation of excess pore water pressure. Soil
densification, replacement by more stable soils, and reducing degree
of saturation.
b) Immediate dissipation of excess porc pressurc, eg., installation of
drains.
c) Reduction of cyclic strain c.g. solidification.
d) Constraint of residual strain.
33
e) Mechanical reinforcement together with equilibrium between gravity
and buoyancy to prevent subsidence and floating.
Countermeasures can be classified into two different categories based on their
principles. Namely -the prevention of liquefaction and the reduction of damage to
facilities due to liquefaction during earthquakes.
The prevention of liquefaction can be achieved by the increase of undrained cyclic
strength as well as by improving the resistance to deformation or by dissipation of
pore water pressure. Resistance against liquefaction can be increased by the
following factors:
Furthermore, liquefaction is not likely to occur the following condition of stress,
deformation and pore water pressure dissipation:
f) Immediate dissipation of exccss pore water pressure
g) Interception of propagation of excess pore water pressure from
liquefied surrounding area
h) Reduction of the shear stress ratio to effective over burden pressure,
by increasing the effective over burden pressure
i) Smaller shear deformation of the ground during earthquake
Densification work will improve resistance against liquefaction of the ground by
increasing the soil density. The effect of the item (g) is also expected for this method.
It is reported that the horizontal earth pressures have been increased afterdensification.
The method tenned soil replacement is the removal of the liquefaction sand deposit
and replacement with good soil which seems non-liqucfiable with regard to the grain
size distribution. Gravel is used as the replaccment because of its grain size
distribution.
34
Furthermore, gravel usually has the effect of item (e) because of its high
permeability. T he solidification method can be considered as Item (c). The effects of-'. n
Items~and~can be expected for this method.
Lowering the ground water table is effective in reducing the degree of saturation of
the soil, as listed in Item (d). Item (g) can be achieved by the increased of
overburden pressure accompanying the lowering the ground water. The dissipation
method is based on the effect on Item (e). Item (f) can also be expected to be
achieved with this method, depending on the arrangement of drains.
Thcre are basically three possibilities to reduce liquefaction hazards when designing
and constructing new buildings or other structures as bridges, tunnels, and roads.
a) Avoid liquefaction susceptible soils
b) Build liquefaction resistant structures
c) Improve the soil
2.8.1 Avoid Liquefaction Susceptible Soils
The first possibility is to avoid construction on liquefaction susceptible soils. There
are various criteria to determine the liquefaction susceptibility of a soil. By
characterizing the soil at a particular building site according to these criteria one can
decide if the site is susceptible to liquefaction and therefore unsuitable for the desired
structure.
2.8.2 Improvement of the Soil
The third option involves mitigation of the liquefaction hazards by improving the
strength, density, and/or drainage characteristics of the soil. This can be done using a
variety of soil improvement techniques. Thc main goal of most soil improvement
techniques used for reducing liquefaction hazards is to avoid large increases in pore
water pressure during earthquake shaking. This can be achieved by densification of
the soil and/or improvement of its drainage capacity.
35
Vibroflotatioll
Vibroflotation involves the use of a vibrating probe that can penetrate granular soil to
depths of over 30 m. The vibrations of the probe cause the grain structure to collapse
thereby densifYing the soil surrounding the probe. To treat an area of potentially
liquefiable soil, the vibroflot is raised and lowered in a grid pattern. Vibro
Replacement is a combination of vibroflotation with a gravel backfill resulting in
stone columns, which not only increases the amount of densification, but provides a
degree of reinforcement and a potentially effective means of drainage.
Dynamic Compaction
Densification by dynamic compaction is performed by dropping a heavy weight of
steel or concrete in a grid pattern from heights of 8 to 30 m. It provides an
economical way of improving soil for mitigation of liquefaction hazards. Local
liquefaction can be initiated beneath the drop point making it easier for the sand
grains to densifY. When the excess pore water pressure from the dynamic loading
dissipates, additional densification occurs.
Stolle Columns
Stone columns are columns of gravel constructed in the ground. Stone columns can
be constructed by the vibroflotation method. They can also be installed in other
ways, for example, with help of a steel casing and a drop hammer as in the Franki
Method. In this approach the steel casing is driven in to the soil and gravel is filled in
from the top and tamped with a drop hammer as the steel casing is successively
withdrawn.
Compaction Piles
Installing compaction piles is a very effective way of improving soil. Compaction
piles are usually made of pre-stressed concrete or timber. Installation of compaction
36
piles both densities and reinforces the soil. The piles are generally installed in a grid
pattern and are generally driven to depth of up to 60 ft.
Compactioll Groutillg
Compaction grouting is a technique whereby a slow-flowing water/sand/cement mix
is injected under pressure into a granular soil. The grout forms a bulb that displaces
and 'hence densities, the surrounding soil. Compaction grouting is a good option if
the foundation of an existing building requires improvement, since it is possible to
inject the grout from the side or at an inclined angle to reach beneath the building.
Draillage Techlliques
Liquefaction hazards can be reduced by increasing the drainage ability of the soil. If
the pore water within the soil can drain freely, the build-up of excess pore water
pressure will be reduced. Drainage techniques include installation of drains of gravel,
sand or synthetic materials. Synthetic wick drains can be installed at various angles,
in contrast to gravel or sand drains that are usually installed vertically. Drainage
techniques are often used in combination with other types of soil improvement
techniques for more effective liquefaction hazard reduction.
2.8.3 Liquefaction Resistant Structure
If it is necessary to construct on liquefaction susceptible soil because of space
restrictions, favorable location, or other reasons, it may be possible to make the
structure liquefaction resistant by designing the foundation elements to resist the
effects of liquefaction. A structure that possesses ductility, has the ability to
accommodate large deformations, adjustable supports for correction of differential
settlements, and having foundation design that can span soft spots can decrease the
amount of damage a structure may suffer in case of liquefaction. To achieve these
features in a building there are various aspects to consider.
37
It is important that all foundation elements in a shallow foundation is tied together to
make the foundation move or settle uniformly, thus decreasing the amount of shear
forces induced in the structural elements resting upon the foundation. A stiff
foundation mat is a good type of shallow foundation, which can transfer loads from
locally liquefied zones to adjacent stronger ground
Buried utilities, such as sewage and water pipes, should have ductile connections to
the structure to accommodate the large movements and settlements that can occur
due to liquefaction.
Liquefaction can cause large lateral loads on pile foundations. Piles driven through a
weak, potentially liquefiable, soil layer to a stronger layer not only have to carry
vertical loads from the superstructure, but must also be able to resist horizontal loads
and bending moments induced by lateral movements if the weak layer liquefies.
Sufficient resistance can be achieved by piles of larger dimensions and/or more
reinforcement. It is important tlmt the piles are connected to the cap in a ductile
mamler that allows some rotation to occur without a failure of the connection. If the
pile connections fail, the cap cannot resist overturning moments from the
superstructure by developing vertical loads in the piles.
2.9 PROBABILITY OF LIQUEFACTION
The likelihood of experiencing liquefaction at a specific location is primarily
influenced by the susceptibility of the soil, the amplitude and duration of ground
shaking and the depth of groundwater. The relative susceptibility of soils within a
particular geologic unit is assigned as discussed. It is recognized that in reality,
natural geologic deposits as well as man-placed fills encompass a range of
liquefaction susceptibilities due to variations of soil type (i.e., grain size
distribution), relative density, etc. Therefore, p0l1ion of a geologic map unit may not
be susceptible to liquefaction, and this should be considered in assessing the
probability of liquefaction at any given location within the unit. In general, we accept
non-susceptible portions to be smaller for higher susceptibilities. This "reality" is
incorporated by a probability factor that quantifies the proportion of a geologic map
38
unit deemed susceptible to liquefaction (i.e., the likelihood of susceptible conditions
existing at any given location within the unit).
2.10 ASSESMENT OF LIQUEFACTION POTENTIAL
2.10.1 Prediction of Liquefaction
The occurrence of liquefaction is affected by various geotechnical factors, which are
classified into three categories: geological conditions, soil properties and ground
motion characteristics. The probability of liquefaction can be determined by the
following criteria.
Historical Criteria
Observations from earlier earthquakes provide a great deal of information about the
liquefaction susceptibility of certain types of soils and sites. Soils that have liquefied
in the past can liquefY again in future earthquakes. If a structure is plmmed to be
constructed a particular site, investigation can be made whether this site was
susceptibk to liquefaction is past earthquake .. Information is available in the form
of maps of areas where liquefaction has occurred in the past and/or is expected to
occur in the future. Maps of sensitive areas, including areas susceptible to
liquefaction are available from different agencies.
Geological Criteria
The type of geologic process that created a soil deposit has a strong influence on its
liquefaction susceptibility. Saturated soil deposits that have been created by
sedimentation in rivers and lakes (fluvial or alluvial deposits), deposition of debris or
eroded material (colluvial deposits), or deposits formed by wind action (aeolian
deposits) can be very liquefaction susceptible. Thcse processes sort particles into
uniform grain sizes and deposit them in loose state which tends to densifY when
shaken by earthquakes. The tendency for densification leads to increasing pore water
pressure and decreasing strength. Man-made soil deposits, particularly those created
by the process of hydraulic filling, may also bc susceptible to liquefaction.
39
Compositional Criteria
Liquefaction susceptibility depends on the soil type. Clayey soil, particularly
sensitive soils, may exhibit strain-softening behavior similar to that of liquefied soil,
but do no liquefy in the same manner as sandy soils do.
Soils composed of particles that are all about the same size are more susceptible to
liquefaction than soils with a wide range of particle sizes. In a soil with many
different size particles, the small particles tend to fill in the vOIds between the bigger
particles thereby reducing the tendency for densification and pore water pressure
development when shaken.
The geologic process described above produce rounded particles. The friction
between angular particles is higher than between rounded particles, hence a soil
deposit with angular particles is normally stronger and less susceptible to
liquefaction.
State Criteria
The initial "state" of a soil is defined by its density and effective stress at the time it
is subjected to rapid loading. At a given effective stress level, loose soils are more
susceptible to liquefaction than dense soils. For a given density, soils at high
effective stresses are generally more susceptible to liquefaction than soils at low
effective stresses.
Major factors affecting the occurrence of liquefaction are provided in Table 2.2
(lGS, 1998). The prediction of liquefaction involves investigating the potential
occurrence of liquefaction of the ground based on information provided in the Table
2.2. Ground conditions and soil properties required for liquefaction potential analysis
have been presented in Table 2.3 and Table 2.4 (lGS, 1998), respectively. In Table
2.3, G/Go is shear modulus ratio, y is shear strain, h is damping, G is shear modulus,
v is Poisons ratio, Vs is shear wave velocity and Vp is primary wave velocity. In
40
Table 2.4, Fe indicates fines content, Dso is mean grain size and Ue is uniformity co-
efficient.
Table 2.2 Factors affecting the occurrence ofliquefaction (JGS, 1998)
Geological Water table, geological age, total stress, effective stress,conditions over consolidation ratio, earth pressure at rest, initial static
shear stress, deformation constraint conditions, boundarycondition against seepage, drainage conditions
oil properties Unit weight, grain size distribution, fine content, mean grainsize, clay content, plasticity index, relative density, structureof skeleton, shear modulus, damping ratio, coefficient ofvolume compressibility, degree of saturation, specificgravity of soil particle
Earthquake Motion Horizontal acceleration, magnitude of earthquake, intensityof seismic shear stress and number of cycles of duration,strain level, direction of shearing
Table 2.3 Information required for various liquefaction evaluations
Parameter Preliminary Method Simplified method Detailed method
Ground conditions Geomorphological water table, Boring water table,conditions log, Soil Boring log, Soil
classification, Unit classification, Unitweight of soil weight of soil
Strength SPT N-value, SPT N-value,characteristics of soil Liquefaction, Liquefaction,-
strength from lab strength from labtest test
Dynamic GIGo - y, h - y, G,deformation E, v, Vs, Vp- -characteristics
Earthquake Maximum ground Assumed basecharacteristics acceleration rock motion-
magnitude
41
Table 2.4 Soil type in various guidelines requiring liquefaction evaluation (JGS,1998)
Guideline Soil type Index property
required
Recommended practice for Dso<2mm FeLNG in ground storage[Japan Fc<35%Gas Association, 1979]
Specification for highway 0.02mm<Dso<2mm Dsobridge, (Japan Road
Association 1990)
Technical standard for port For sands with low Dc Grain size
and harbor facilities (Japan 0.02mm<Dso<2mm distribution
Port and Harbor Association, For sands with high Dc curve
1989) O.0Imm<Dso<3mm
Recommendations for design Fc<35% other soils desired for Dsoof building foundations, evaluations: silt with low
AIJ(l988 and 1990) plasticity, silt having a water
content close to liquid limit,
gravel with significant Fe, gravel
sandwiched by impermeable
soils
2.10.2 Cyclic Strength of Soils
Definition and determination of cyclic strength of soil has been presented below:
a) Soil liquefaction may be defined as the state of soil at which soil
looses its shear strength and subsequently behaves like a liquid
b) It is generally observed that the pore water pressure build up steadily
as the cyclic axial stress is applied and eventually approaches a value
equal to the initially applied confining pressure, thereby producing an
axial strain of about 5% in double amplitude (DA). Such a state is
referred to as initial liquefaction or simply liquefaction
42
c) For loose sand the initial liquefaction can certainly be taken as a state
of softening because infinitely large deformation is produced
suddenly with complete loss of strength during or immediately
following the 100% pore water pressure build-up.
d) For medium dense to dense sand a state of softening is produced with
the build-up of 100% pore water pressure, accompanied by about 5%
DA axial strain. However, deformation there after does not increase
indefinitely. Complete loss of strength does not take place in the
simple even after the on set of initial liquefaction.
e) In silty sand or sandy silts containing some amount of fines, pore
water pressure does not develop completely. Rather it stops
developing at about 90% to 95% of the initial confining stress ..
However, a sizable amount of cyclic strain is observed to develop
indicating considerable softening taking place in this soil.
f) '. Therefore, the occurrence of 5% DA axial strain in the cyclic triaxial
test is used as a criterion to define coherently the state of cyclic
softening or liquefaction of soils.
g) In order to specifY the on set of liquefaction or development of 5%
DA axial strain the number of load cycles must be specified in
constant amplitude uniform cyclic loading. In principle the number of
load cycles can be set arbitrarily. However, appropriate correction
factor is to be incorporated to account for earthquake loading, which
is the major cause of soil liquefaction in real problem. The onset
condition of liquefaction or cyclic softening as specified in terms of
the magnitude of cyclic stress ratio required to produce 5% DA axial
strain in 20 cycles of uniform load application. This cyclic stress ratio
is referred to simply as cyclic strength.
h) In order to evaluate the irregular nature of seismic loading it is
customary to consider 10 or 20 load cycles in view of the typical
number of significant cycles present in many actual time histories of
acceleration recorded during past earthquakes.
43
i) Thus the cyclic strength of a soil mass may bc defined as the stress ",
ratio causing 5% DA strain in 20 cycles of uniform load application,
2.10.3 Conditions for Liquefaction to Occur
The following conditions should be satisfied for liquefaction to occur.
a) Soil deposit should be loose and granular such as silty sand or sandy
silt with or without fine content
b) The ground water table is shallow and soil should be saturated,
c) Load application should be repeated and cyclic in nature so that pore
water pressures build gradually,
d) Loading rate should be high enough to establish undrained condition
in the cohesion less soil mass, The earthquake intensity is sufficiently
high and the duration of earthquake shaking is sufficiently long.
2.10.4 Liquefaction Susceptibility
Not all soils are susceptible to liquefaction. There are several criteria by which
liquefaction susceptible can be judged, these includes historical, geological and state
criteria, Youd and Perkins (1978) have addressed the liquefaction susceptibility of
various tyjJes of soil deposits by assigning a qualitative susceptibility rating based
upon general depositional environment and geologic age of the deposit The relative
susceptibility ratings of Youd and Perkins (1978) have becn shown in Table 2.5,
From Table 2.5, it is seen that recently deposited relatively unconsolidated soils such
as Holocene-age river channel, flood plain and delta deposits and uncomplicated
artificial fills located below the groundwater table have high to very high
liquefaction susceptibility,
Sands and silty sands are particularly susceptible to liquefaction. Silts and gravels are
also susceptible to liquefaction, and some sensitive clay has exhibited liquefaction-
type strength losses (Updike et aI., 1988). Permanent ground displacements due to
44-.(
',) .
lateral spreads or flow slides and differential settlement is commonly considered
significant potential hazards associated with liquefaction
The initial step of the liquefaction hazard evaluation is to characterize the relative
liquefaction susceptibility of the soil/geologic conditions of a region or sub-region.
Susceptibility is characterized utilizing gcologic map information and the
classification system presented by Youd and Perkins (1978) as summarized in Table
2.5. The geologic maps typically identifY the age, depositional environment, and
material type for a particular mapped geologic unit. Based on these charactcristics, a
relative liquefaction susceptibility rating (e.g., very low to very high) is assigned
from Table 2.5 to each soil type. Mapped areas of geologic materials characterized as
rock or rock-like are considered for the analysis to present no liquefaction hazard.
Liquefaction susceptibility maps produced for certain regions may alternatively be
utilized in the hazard analysis.
2.10.5 Steps in Liquefaction Prediction
The following are four mam steps in the prediction of liquefaction and its
consequences
a) Estimation of the stress state before the earthquake and liquefaction
resistance.
b) Estimation of seismic shear stresses caused by the earthquake.
c) Evaluation of liquefaction susceptibility, excess pore water pressure,
and defOlmation of ground, and
d) Evaluation of the consequences of liquefaction on soil structure
systems, such as permanent deformation and stability.
In the simplified method, the liquefaction strength is estimated either from in-situ
tests and laboratory tests and the factor of safety against liquefaction is estimated by
comparing the liquefaction strength with the cyclic stress ratio developed in the
deposit during an earthquake. Figure 2.9 shows the flowchart of the method.
45
Table 2.5 Liquefaction susceptibility of sedimentary deposits (Youd and Perkins, 1978)
Types of deposit General Likelihood that cohesion less sediments whendistribution of saturated would be Susceptible to liquefaction (bycohesion less age of deposits)sediments in
Holocene Pleistocene Pre-deposits < 500 yrPleistoceneModern < 11 Ka 11 Ka-2 Ma>2 Ma
(a) Continental DepositsRiver channel Locally variable Very High High Low Very LowFlood plain Locally variable High Moderate Low Very LowAlluvial fan and plain Widespread Moderate Low Low Very LowMarine terraces and plains Widespread - Low Very Low Very LowDelta and fan-delta Widespread High Moderate Low Very LowLacustrine and playa Variable High Moderate Low Very LowColluvium Variable High Moderate Low Very LowTalus Widespread Low Low Very Low Very LowDunes Widespread High Moderate Low Very LowLoess Variable High High High UnknownGlacial till Variable Low Low Very Low Very LowTuff Rare Low Low Very Low Very LowTephra Widespread High High - -Residual soils Rare Low Low Very Low Very LowSebka Locally variable High Moderate Low Very Low
(b) Coastal ZoneDelta Widespread Very High High Low Very LowEsturine Locally variable High Moderate Low Very LowBeach - - - - -High Wave Energy Widespread Moderate Low Very Low Very LowLigh Wave Energy Widespread High Moderate Low Very LowLagoonal Locally variable High Moderate Low Very LowFore shore Locally variable High Moderate Low Very Low
(c) ArtificialUncompacted Fill Variable Very High - - -Compacted Fill Variable Low - - -
46
Number ofCycles N
EarthquakeMagnitude, M
Earthquake Characteristics
Maximum GroundAcceleration am"
TotalStress
Equivalent Shear Stress RatioLiquefaction Strength Ratio
EffectiveStress
Ground Characteristics
Fine content, F,Mean GrainSize, D50
2.10.6 Liquefaction Potential Analysis
Figure 2.9 Flowchart of simplified method using SPT N-value (Yoshimi, 1991)
Evaluation of Liquefactin Potential
47
Ground vibration caused by earthquake often lead to the compaction of cohesion less
soil and associated settlement of tlle ground surface (Ishihara and Qgawa, 1978).
Loosely packed, saturated sands and silts tend to loose all strength and behave like
fluids during strong earthquakes. When such materials are subjected to shock,
dcnsification occurs. During relatively short duration of an earthquake, drainage
cannot be achieved, and this densification leads to the development of excessive pore
pressure, which causes the soil mass to act as a heavy fluid with practically no shear
strength (Wang and Timlaw, 1994). During earthquake water moves upwards from
tile voids to the ground surface, where it emerges to form sand boils. Saturated sand
coarse sand, fine sand, silty sand and even sandy silt can all liquefy when there is
insufficient drainage boundary around them. The occurrence of liquefaction is
affected by various geotechnical factors, which are classified into three categories:
soil properties, geological conditions and ground motion characteristics as described
in article 2.10.1.
Several laboratory tests are in practice to estimate the liquefaction potential of soils
such as dynamic triaxial test, cyclic simple shear test and shaking table test.
Similarly, several in-situ empirical criteria have been developed over the years based
on standard penetration test (SPT), cone penetration test (CPT) and shear wave
velocity measurement for the assessment of liquefaction potential (Seed and Idriss,
1971; Seed et a!., 1985; Iwasaki et a!., 1982; Seed and Peacock, 1971; Yond and
Idriss, 200 1; Robertson and Campanella, 1985).
2.10.7 Estimation of Liquefaction Susceptibility Using Different Methods
Liquefaction susceptibility can be determined using different methods such as
geomorphological information, soil characteristics and SPT N-value.
Geomorphological Information
Deposits prone to liquefy may be roughly identified based on geographical
information. Table 2.6 shows such a chart in which liquefaction susceptibilities are
ranked for various geomorphological conditions (Yasuda, 1988). Sites on a
reclaimed fill or an abandoned river channel show high susceptibility, while sites on
a hill do not. Although rough and usable only for preliminary estimation, the method
may effectively be used for micro-zoning purposes, and for selecting sites within a
large area for which more detailed investigation is planned.
Table 2.6 Liquefaction susceptibility based on geomorphological units (Yasuda,1988)
Liquefaction potential Geomorphological unit.
High Reclaimed fill, present and old river beds, young natural
levee, interdune lowland
Moderate Lowlands other than above: fan, nature levee, sand
dune, flood plain, beach
Low Terrace, hill, mountain
48
Soil Characteristics
As a general guide, the characteristics of liquefiable soils are presented in Table 2.7
(Rao, 2003). The liquefaction susceptibility can be estimated based on the soil
properties given in Table 2.7 by comparing existing soil properties.
Table 2.7 Vulnerable soil properties for liquefaction (Rao, 2003)
Properties Vulnerable soil properties
Mean size, dso (mm) 0.02 to 1.00
Fines content (d :s0.005 mm) < 10 %
Uniformity coefficient, Cu <10
Relative density, Dr <75 %
Plastic index, Ip < 10
Intensity >VI
Depth < IS m
SPTN-Value
If the SPT N-value determined by the in-situ test exceeds a specific value, soil
liquefaction may not occur under intensive earthquake shaking. Even if the soil
liquefaction occurs under that condition, the resulting damage to structures is
expected to be minor. Such a threshold N-value may be called the critical N-value.
With this critical N-value, together with the soil classification the possibility of
liquefaction may be examined without considering the intensity of earthquake
shaking. Several guidelines adopting the above criterion are summarized in Figure
2.10 (Yasuda, 1988).
49
50
Table 2.8 Liquefaction criteria for fine-grained soils (Andrews and Martin, 2000)
3530252015
Fine content (%)
105
I Not Liquefiable I
'" i'.."-8
Liquefiable I.
20
15"::J"@>,
10Z"@.g.;::u 5
Clay content Liquid Limit <32 Liquid Limit 232
Clay content <10% Susceptible May be susceptible (conductadditional testing)
Clay content 210% May be susceptible (conduct Not susceptibleadditional testing)
2.10.9 Liquefaction Potential Analysis Based on SPT N-value Using DifferentMethods
25
Recovery of high-quality undisturbed samples and laboratory testing is the most
reliable procedure for accurate evolution of the cyclic strength of sand. However,
obtaining sand samples from deposits below the growldwater table is a costly
operation, and can be justified only for an important construction project. Therefore,
Criteria for liquefaction potential of silty sales have been proposed by Andrews and
Martin, 2000. Their criteria have been presented in Table 2.8. Clay content has been
defined as 0.002 mm, Liquid limit has been defined as Casagrande Method.
2.10.8 Liquefaction Criteria for Fine Grained Soils
Figure 2.10 Critical SPT N-value and fines content for liquefiable soils (Yasuda,1988)
a simpler and more economically feasible procedure is used to determine the cyclic
resistance of soils.
Liquefactioll Potelltial, FL
Liquefaction can be analyzed by a simple comparison of the seismically induced
shear stress with the similarly expressed shear stress required to cause initial
liquefaction or whatever level of shear strain amplitude is deemed intolerable in
design. Usually, the occurrence of 5 % DA axial strain is adopted to define the cyclic
strength consistent with 100 % pore water pressured build up as mentioned in article
2.10 in this chapter. Thus, the liquefaction potential of a sand deposit is evaluated in
term offactor of safety FL defined as stated in Equation (2.1)
(2.1)
where, (GDJ2G~)20 is cyclic strength and ("tmax)avlGy' is disturbing stress.
The determination procedures of cyclic strength and the corresponding disturbing
stress have been discussed in the later sections.
If FL :'>1.0,liquefaction is said to occur and otherwise liquefaction does not occur.
The factor of safety obtained in this way is generally Used to identify the depth to
which liquefaction is expected to occur in a future earthquake. This information is
necessary if some cowltermeasure is to be implemented in an in situ deposit of sands.
Graphical Method
One method to accomplish this is to take advantage of the penetration resistance of
the Standard Penetration Test (SPT), which has found world-wide use in the
investigation of in-situ characteristics of soil deposits because:
51
a) The SPT N-value is an index property reflecting soil density and
fabric, and thus could have a good correlation with liquefaction
strength.
b) The SPT is primarily shear strength test under essentially undrained
conditions, while many of the other field tests are conducted under
drained conditions.
c) Numerous case histories of soil liquefaction during past earthquakes
are available, based on which empirical correlations between SPT N-
value and liquefaction strength are developed. Besides, no reliable
empirical correlation exists in which index properties other than SPT
N-value are used.
d) The SPT yields representative samples of soil from which index
properiies such as mean grain size and fine content can readily be
.. determined. Many of the other in-situ tests, in contrast, cannot recover
soil samples.
Although there are a lot of reasons behind using SPT N-value for liquefaction
potential analysis, one must be aware the following limitations:
a) The apparatus and the procedure have not been standardized enough
to be the 'standard'. Thus, deferent test methods together with
operator error may lead to considerable variation in measured SPT N-
value.
b) The confining pressure has significant effects on SPT N-values.
c) The liquefaction strength may vary depending on soil type (fines
content, D50, and clay content) even ifN-values are the same.
d) Empirical con-elation is required to estimate liquefaction strength
from SPT N-values. Such an empirical correlation leads to some
variation in estimated liquefaction strength.
There are basically two approaches for establishing the con-elation of the blow count
value N of the SPT with the cyclic strength of soils in the field. The first approach is
52
53
where, 'av is the amplitude of average shear stress taken over the time history of
seismic motions 'max.1 /6' v denotes the amplitude of maximum shear stress required to
cause liquefaction. The N, value plotted on the x-axis is obtained by correcting a
measured N value to that cOlTesponding to an overburden pressure of I kg/em' = 98
kPa. In Figure 2.11, (N')60 is used to indicate explicitly the blow count value
obtained with a driving energy 60% of the theoretical free-fall energy hammer. (Rate
of energy transmission in Japanese practice is considered to be 1.2 times as great as
in USA practice, therefore the relation N1'" 0.833(Nl)60 can be used to convert the N
value of SPT between the two practice as indicated on the x-axis of Figure 2.11)
(2.2)[
(J"dl J '" _1__, "_'.1 '" _, m_",_.12~ ' 0.65 (J"v' (J" v 'v 0 20
based on investigation of whether or not in situ soil deposits have actually developed
liquefaction during past earthquakes. With an intensity of shaking estimated by some
appropriate procedure, values of cyclic stress ratio believed to have occurred in situ
soil deposits during an earthquake can be estimated and compared with the
penetration resistance of a sandy soil at any depth of an in situ deposit. Since it is
known whether or not liquefaction induced ground damage has occurred, it is
possible to establish a threshold relation between the cyclic stress ratio and the N
value of the ST test. Such as an approach was developed by Seed (1979) on the basis
of vast number field performance data on sand deposits exposed to strong shaking
during recent earthquakes. The relation derived by Seed et. al. (1983) based on more
comprehensive data as shown in Figure 2.11, which plots the cyclic stress ratio
causing initial liquefaction against the normalized N value. The three kinds of stress
ratio are shown on the y-axis, based on past studies indicating this three stress ratio
to be approximately equal
Figure 2.11 Summary charts for evaluation of the cyclic strength of sands based onthe normalized SPT N-value (Ishihara, 1993).
(2.3)
,0.7 Seed at al. I,
(1983) III
" I,!! I
1 O.G~ Kokusho
, at 81. (1983)I
I. ITokimateu and I
~I0.5 Yoshiml (19831 I
I1 "'(•• 3% IC\p. 0.15 mmI
-I~0.4~-O.35mm
••'""bS 0.3~ Japanese code.!! of bridge design
"'e Q'~i! Shibata (1981)
"."uis 0.1
0 10 '0 30 40 SONormalized N value, N, •• 0.833 (N,)6Il
54
The second method to establish a correlation between the cyclic strength and N value
is to collect a large number of laboratory test data on the cyclic strength of
undisturbed soil samples recovered from deposits of known penetration resistance.
An empirical correlation between these two quantities can easily be established: one
of the relations incorporated in the Japanese code of bridge design (Tatsuoka,
Iwasaki, Tokida, Yasuda, Hirose, Imai & Kon-no, 1980) was as equation (2.3) and
Japanese Code of Bridge Design
(2.4).
[adl J ~ (0.35J--, = 0.0676"\j N, + 0.22510glO --
2ao 20 D,o
For 0.04 mm ~ Dso < 0.6 mm
(2.5)
(2.4)
.-
....•.••. Peck, el 01.,1'374--- ~9~~and Wh,lfTlon.
- - SkemPlol\.19S6CoQf~oe sottd,
-- Sk~"",:.lIO". 1986Fine ,ands
-'- Ske.,-.p.ton.I'366O.C. sondJ
_ •.- Seed, 1979Dr-5O.1 •
•• ~•• - Seed,l979Dr<70-' ••
2.5
3.0
0.5d?•....It! 1.0
u;~:! 1.5<n"8 2.0;:~
(20"'",J = 0.0676JN: -0.05ao 20
SPT Overburden Correction Foetor. CN00 o.~ 1.0 1.5 2.0 2.5
Figure 2.12 CN factors by various investigations (ASTM D 1586)
where, 6v' is the effective overburden pressure in Kgf / cm2
For 0.6 mm :SDso < 1.5 mm
55
where, Dso is the mean particle diameter in mm, N I IS obtained through the
correction factor CN defined as equation (2.5):
Similar, correlations has been provided in ASTM D (1586) as shown in Figure 2.12,
In this Figure different correlations developed by different researchers has been
presented.
The cyclic strength obtained from equations (2.3 and 2.4) was plotted against N1 in
Figure 2.1 I for typical grain sizes ofDso = 0.15 mm and 0.35 mm. Equation (2.3 and
2.4) was derived in the form of linear correlation between the laboratory determined
cyclic strength and relative density, Dr. It was rewritten later in the form of Equation
56
Chinese Criterion
(2.6)[
Udl J = Tm".l = 9.5N1 +0.466N1'
2u' uv' 1000o
Similar attempts were made by Kokusho, Yoshida and Esashi (1983) on the basis of
a vast body of laboratory test data on clean sands. Relation based on a large body of
field performance data obtained mainly in Japan were proposed by Shibata (1981)
and Tokimatsu and Yoshimi (1983), and they are also shown in Figure 2.11. On the
basis of recent large earthquakes in China, the criterion for identifYing sandy
deposits as being susceptible or immune to liquefaction was presented in the form of
a code requirement. Through some numerical manipulation (Ishihara, 1990), the
Chinese criterion can be expressed as equation (2.6)
This relation is also shown in Figure 2.11. From the cluster of curves proposed by
various researchers, it was apparent that the relation fall in approximately the same
range for N, = 10-25, where actual data were available in abundance.
(2.3 and 2.4) by using the relationD,. = 16.[N;. Therefore, Equation (2.3 and 2.4)
are valid in the range of relative density less than about 70%, where the cyclic
strength was related linearly to relative density. In terms of SPT blow count Equation
(2.3 and 2.4) should be considered to hold true for the N,<20.
In most of the correlations epitomized above, effects of the presence of fines were
allowed for in such a way that the penetration resistance becomes smaller with
increasing fines content if soils possess equal cyclic strength. At constant penetration
resistance, soils were observed to have increasing cyclic strength with increasing
fines content as shown schematically in Figure 2.l3(lshihara, 1993). Thus, given a
correlation such as equations (2.3 and 2.4) in terms of a parameter associated with
grading such as fines content Fe or average diameter Dso , it is possible to determine
the amount of the shift tlN I Shown in Figure 2.13 as a function of fines content. The
(2.8)
(2.7)
N,N,
SandwithfInes
fIN,. Fe)
For 5%:s Fc:S 20%
Clean sandf(N1,O)
57
Figure 2.13 Definition of an increment ofNlvalue, allowing for the effects of fines(Ishihara, 1993).
value of ~N I was interpreted as a decrease in N} value for clean sands so as to have
the same cyclic strength as silty sands. Thus, if the cyclic strength for fines-
containing sands is f(Nr, Fe), the increment ~NI was determined as equation (2.7).
The increment ~NI thus obtained from the complied data by Seed and De Alba
(1986) was plotted in Figure 2.14. By connection of these points, a curve is drawn in
Figure 2.14 that could be used for practical purposes. The same argument could be
developed to obtain the increment ~N I associated with residual strength. In this case,
the value ~N I implies the change of N I value required by fines-containing sand to
have the same residual strength as clean sand. The increment related to the cyclic
strength was different from that associated with the residual strength. A curve of ~N I
for the residual strength was obtained from the values suggested by Seed & Harder
(1990), and was shown in Figure 2.13. If more than 5% fines are seen to exist in the
soil, the measured N I value should be increased using Equation 2.10 and 2.11.
(2.9)
(2.10)
504030
Based onresidual strength
• : Seed and Do Alba11986)
G : Seed Ind HatdtlrI1ml
20Finss content. F; (%1
10
Based oncyclic strength
\
oo
For Fe > 20%
t.N, = 7.5
The method of correction described above was based on the assumption that the
effects of fines could be taken into account in terms of grading parameters such as
fines content and mean diameter. However, as pointed out above, the grading of soils
was not necessary an essential factor influencing the cyclic strength: the nature of the
fines, as represented by plasticity index, is a more physically meaningful parameter
governing the strength mobilized in cyclic loading. If this effect was to be
incorporated into the cyclic strength-penetration resistance relation, it was necessary
to know how the penetration resistance was influenced by the plasticity of fines.
However, there are no relevant test data.
Figure 2.14 Increment t.N, value as a function of fines content (Ishihara, 1993)
58
Under the circumstances described, the only way at present to elucidate this relation
would be first to evaluate the cyclic strength of in situ soil deposits through the
procedures described above, where effects of fines are allowed for in terms of he
grading indices, and then to modify it in accordance with a relation such as that
shown in Figure 2.15 (Ishihara, 1993). In utilizing this relation, it would be
(2.11)
60
"
••••
""•
•
"c : Bentonite- based0: Kaolinite.I.: Loom",: Tailings.: Undis turbed
tailings
10 20 30 40 soPlasticity index, Jp
".(at, "" 50 KPa )6 •• 0.53-1.60
•v-•
().5
59
o o
expedient to normalize the cyclic strength at any plasticity to the cyclic strength at
low plasticity index «10). The curve modified in this way is shown in Figure 2.16
(Ishihara, 1993).
If the plasticity index (Ip) of the fines is found to be greater than 10, further
correction must be made for the cyclic strength by the use of Equation (2.11) givenbelow:
where, R is resistance cyclic strength of soil at a given depth and Ip is plasticity index(%).
Figure 2.15 Effects of plasticity index on the cyclic strength of fines containing sand(Ishihara, 1993).
60
60504030
Plasticity Index, It>
20'aa
c
.. .~ _0-~ -i ~ '.0~ ~
I
a) By means of SPT, penetration resistance N1 is obtained, together with the
fines content Fe or mean diameter D50 for the soils in question, throughout the
depth at a given site. If necessary, the plasticity index of the fines fraction
must be determined.
b) If the material was identified as clean sand with fines content less 5%, the
cyclic strength is d~termined from the chart shown in Figure 2.11 and
Equations 2.3 and 2.4. If more than 5% fines are shown to exist in the soil,
measured N I values should be increased based on the chart shown in Figure
2.14 .Then, using of the chart in Figure 2.11 and Equation 2.3 and 2.4, the
cyclic strength is determined. If the plasticity index of the fines is found to be
greater than Ip=IO, further correction must be made for the cyclic strength
using the chart in Figure 2.16. Experience had shown that most sandy soils in
alluvial deposits or man made fills possess a plasticity index less than IS;
therefore, the correction in this regard may not change the cyclic strength
appreciably.
Figure 2.16 Chart for modification of cyclic strength allowing for the effects ofplasticity index (Ishihara, 1993).
With the background information as given above, the procedures to determine the
cyclic strength of the soil in a given deposit could be summarized as follows.
•
(2.12)
(Tm311)dr4= --
(rlllaJ.)'
(e)
o
(b)
Maximum Shear Stress
(a)
N
( )::::::: QmaxO'v
'max rg
Disturbing stress
Figure 2.17 Simplified method for calculating shear / disturbing stress (Seed andIdriss, 1982)
61
The cyclic shear stress induced at any point in level ground during an earthquake due
to the upward propagation of shear waves can be assessed by Seed and Idriss (1982).
This leads to a simplified procedure for evaluation the induced shear stresses. If a
soil column of a depth z is assumed to move horizontally and if the peak horizontal
acceleration on the ground surface is amax as a rigid body shown in Figure 2.17, the
maximum shear stress in the soil element, ('max)" acting at the bottom of the soil
column is given by the Equation (2.12).
where, g is gravity; Oy is total overburden pressure defined by yz; y is submerged unit
weight of soil and z is depth of the ground surface.
In reality, however, because the soil column behaves as a deformable body, the
actual shear stress will be less than ('max), and might be expressed as equation (2.13)
(2.13)
(2.15)
(2.14)
(2.16)
0.7 0.8 0.9 1.000 0.1 0.2 0.3 0.4
10
20
30
~ ~o RANGE FOR DIFFERENT~ SOil PROFILESx 50>-~wc
60
70
80
90
100
Figure 2.18 Range of value ofrd different soil profiles (Seed and Idriss, 1982)
in which, rd is stress reduction coefficient (rd= 1.0 for rock).
Grnax al'(rmax)d =.'---rdg
Otherwise, computations of the value of rd for a wide variety of earthquake motions
and soil conditions having sand have shown Figure 2.18.
Iwassaki (1978) proposed the following relation for rd as stated in Equation (2.14).
rd = 1-0.015z
( C GmaxCJvTmax)uv = ---rd
g
where, C = 0.65 or 0.1 (M-I), here M is earthquake magnitude.
For average val ue
62
(2.17)
TIME
0.65 Tr,lcJX
Generally, C value is taken as 0.65 as shown in Figure 2.19. The actual time history
of shear stress at any depth in a soil deposit during an earthquake will have an
irregular form such as that in shown in Figure 2.19 (Seed and Idriss, 1982). From
such relationships it is necessary to determine the equivalent uniform average shear
stress. By appropriate weighing of the individual stress cycles, based on laboratory
test data, this determination can readily be made. However, after making these
detenninations for a number of different cases it has been found that with a
reasonable degree of accuracy, the average equivalent uniform shear stress, 'av is
about 65 % of the maximum shear stress, 'max. Combining this result with the above
expression for 'max, the average cyclic stress ratio ('av/cr' 0) induced by an earthquake
is given by the expression (Seed and Idriss, 1982).
Figure 2.19 Time history of shear stresses during earthquake (Seed and Idriss,1982).
63
Dividing both sides of Equation (2.16) by cry'
By means of SPT, penetration resistance (N 1) is obtained, together with the fines
content (Fe) or mean diameter (Dso) for the soils in question, throughout the depth at
a given site. If necessary, the plasticity index (Ip) of the fine fraction is alsodetermined.
The effects of soil type on the liquefaction strength are often evaluated using such
factors as fines content Fc and mean grain size 050. Some guidelines adopt clay
content and plasticity index, Ip to limit types of the soil prone to liquefy. Thus, some
tests may be made to determine these properties. A sieve analysis on samples from
the SPT tests provides information concerning fine content and mean grain size. This
information may be estimated from Table 2.9 based on soil type only, if the result of
sieve analysis is unavailable. However, Table 2. I0 (Coduto, 2002) shows present
typical unit weight of the soil sampl~s. One must be aware of the enor associated
with this estimation because of the variability in the figure listed.
Since unit weight of a sandy soil needs to be determined from undisturbed samples,
it was not possible to determine the unit weight directly in the present research. As a
result, Table 2.9 and Table 2.10 are used for assuming saturated unit weight, Y'oI. dry
unit weight, Ydry, mean grain size, 050 and fines content, Fewherever necessary. Table
2.11 (Peck et. aI., 1974) shows the correlation between penetration resistance of
cohesionless and cohesive soil.
Table 2.9 Representative unit weight, mean grain size, and fines content forvarious soil types (JRA, 1990 and JSCE, 1986)
Soil type Unit weightBelow ground Above ground Mean grain
Fines contentwater table water table sIze
Fe (%)(KN/m) (KN/m) 050 (mm)
Surface soil 17.0 15.0 0.020 100Clay 15.0 14.0 100silt 17.5 15.5 0.025 90Sandy silt 18.0 16.0 0.040 70Silty fine
18.0 16.0 0.070 50sandVery fine
18.5 16.5 0.100 20sandFine sand 19.5 17.5 0.150 10Medium sand 20.0 18.0 0.350 5Coarse sand 20.0 18.0 0.600 0Sandy gravel 21.0 19.0 2.000 0
64
Table 2.10 Typical unit weights of soil (Coduto, 2002).
Soil type Unified soil Unit weight, y
classification Above ground Below ground
water table water table
(kN/mJ) (kN/mJ
)
Poorly graded sand SP 15.0-19.5 19.0-21.0
Well graded sand SW 15.0-21.0 19.0-23.0
Silty sand SM 12.5-21.0 17.5-22.0
Clayey sand SC 13.5-20.5 17.5-21.0
Low plastic silt ML 11.5-17.5 12.5-20.5
High plastic silt MH 11.5-17.5 11.5-20.5
Low plastic clay CL 12.5-17.5 11.5-20.5
High plastic clay CH 12.5-17.5 11.0-19.5
Table 2.11 Correlation between relative density and penetration resistance (Peck et.a!., 1974).
Sand Clay
Number of Blows/ft Relative Number ofblows/ft
N Density (Dr) NConsistency
0-4 Very loose Below 2 Very soft
4-10 Loose 2-4 Soft
10-30 Medium 4-8 Medium
30-50 Dense 8-15 Stiff
15-30 Very stiffOver 50 Very dense
Over 30 Hard
65
Chapter Three
DEVELOPMENT OFRECLAIMED AREAS IN DHAKA CITY
3.1 GENERAL
Planned development along with proper mobilization and appropriate utilization of
all available resources is crucial for the overall socio-economic development in
contemporary modern society. The process of resource utilization depends on the
level of technology with a certain degree of modernisation and that again depends
greatly on the rate of urbanization and urban development. Therefore, urbanization
becomes an essential socio-economic phenomenon in countries all over the world.
However, healthy urbanization needs proper planning with adequate emphasis on
Various aspects of the total environment because without proper planning and due
consideration on environmental consequences, urbanization often turns out to be a
problem in the process of achieving development.
The capital city Dhaka has experienced extremely rapid population growth. This has
occurred primarily because most administrative functions and civil employments,
education, financial and banking services, international commerce and business
services are largely concentrated in Dhaka. Continuous influx of rural people from
different parts of the country greatly contributes to the accelerated growth of Dhaka
population. In order to lessen the pressure of the city's population on housing,
transportation, utilities and civic facilities, Rajdhani Unnayan Kartripakhha
(RAJUK) and other private agencies undertook a number of initiatives for expanding
the city area mostly in the northern direction. "Ultara Residential Model Town (3rd
Phase) Project" and the "Purbachal New Town Project" are the recent initiatives that
RAJUK intends to implement in line with "1997 DMDP-RAJUK Master Plan".
Bashundhara is the recent initiative that Bashundhara Group (Private Agency)
intends to implement in line with the Bashundhara Group plan according to RAJUK
and City Corporation. There are many other reclaimed areas in and around Dhaka
66
city Jamuna City, Madhumati Model Town, Rupayan, Nikunja, Banasree, Mirpur
DOHS, Banani old DOHS etc.
This chapter deals with the development procedure of reclaimed areas, sources and
characterdics of filling materials and locations of reclaimed areas in and Dhaka city.
A rational method for the development of reclaimed areas has also been proposed
based on the current land development practice and available literature.
3.2 RECLAIMED AREAS IN DHAKA CITY
There are many reclaimed areas in and around Dhaka City. Many of them has been
surveyed in the present study to locate them in the Dhaka City map. The global
positioning has been determined by GPS. Area of the project, filling procedure,
sources of filing materials and their characteristics were also surveyed. The survey
data have been presented in Table 3.1. But in many cases data are not available since
the owner of the projects does not like to provide information about their project.
Many of the areas are being developed and the area is expanding all the time keeping
up with the demand. The filling depth varies between 2.8 m to 12.0 m and the filling
material in most cases is hydraulic fill. Positions of the reclaimed areas in Dhaka city
has been marked by red circle on the Dhaka city map as shown in Figure 3.1. It is
seen that there are many areas in the city distributed all over the city. It means that
the proper development of such areas is very important with respect to the
economical aspect and safety of the people.
67
Table 3.1 Location of reclaimed areas of in and around Dhaka city.
Name of Reclaimed Latitude Longitude Area Filling Source of FillingArea (N) (E) (acre) depth materials method
(m)Modhumati Model 23°47.46' 90°18.25' 500 8-11 Dhaleswary BargeTown . fiverTown View 23°47.42' 90°18.70' - 5-9 - BargeResidential ProjectUttara Model Town 23°52.30' 90°22.77' 2010 3-6 Dhaleswary Barge(3,d Phase) flver,
BurigangaPurbachal New 23°50.37' 90°28.44' 6000 4-8 Shitalakhya, BargeTown BurigangaJamuna City 23°50.01 ' 90°26.27' - 4-10 - Barge
Pink City 23°49.97' 90°27.80' - 4-11 - Barge
MirpurDOHS 23°50.18' 90°22.04' 74 2-5 - Truck
Banasree 23°45.97' 90°25.58' - 3-9 - Truck
Banorupa 23°50.21' 90°25.13' - --- - BargeResidential ProjectAshulia Model 23°53.55' 90°21.68' - --- - -TownBashundhara 23°48.69' 90°25.84' - 4-11 - Truck &
BargeKeraniganj 23°43.23' 90°20.90' - 4-6 Buriganga Barge(Kholamora) fiver
Somali Abasion 23°50.00' 90°27.51 ' - - - Barge
Concord Lake 23°49.98' 90°26.12' - - - BargeView .
Tamanna River 23°49.23' 90°20.48' - - - BargevIew
68
o s
Location Identification Location IdentificationModhumoti Model
P.OI Banasree P-OSTownTown View Residential
P-02 Banorupa ResidentialP-09Prjeet Project
Uttara Model Town (3rdP.03 Ashulia Model Town polO
Phase) Bashundhara P-IIPurbachal New Town P-04 Keraniganj (Kholamora) P-12Jamuna City p-os Somali Abasion p.J3Pink City P.06 Concord Lake View P-14Mirpur DOHS P-O? Tamanna River View polS
Figure 3.1 Location of reclaimed areas in Dhaka City.
69
3.3 SOURCES OF FILLING MATERIAL
Many of the low-lying areas around the city of Dhaka are now being filled for
housing by developers. Huge volume of soil is required to fill for the reclaimed sites
of Uttara Model Town (3rd Phase), Purbachal New Town, Bashundhara, Mirpur
DOHS, Bansree, Banani old DOHS etc. Because of the severe road traffic congestion
around the sites the filling soil has to come through river. The filled soil has to be
collected.from adjacent river sources such as Turag, Buriganga, Dhaleshwari,
Sitalakhaya and Meglma.
The following methods are presently used for filling these low-lying areas:
(I) Soil being carried by country boats from remote sources and manually
dumped at the filling site.
(2) Soil being carried by Trucks from remote sources and manually dumped at
the filling site.
(3) Soil is collected from riverbeds by cutter-suction dredging into a barge,
which is carried to the nearest river site. Soil is then pumped through pipes in
a slurry form after mixing with water, and transferred to the point of
deposition.
(4) Soil is dredged from riverbed by cutter suction dredging and directly pumped
to the filling site thorough discharge pipes.
In most cases where large volume of fill materials is required, a hydraulic filling
procedure similar to method No.(3) or method No.(4) is followed. But the site of
Uttara Model Town (Third Phase) and Purbachal New Town under RAJUK and
Bashundhara, Bansree, Keraniganj under private agency are filled by method No.
(3). Mirpur DOHS under government agency is filled by method No. (2).
3.4 CRITERIA OF FILL MATERIAL
The presence of fines in a hydraulic fill means greater compressibility and greater
difficulty in compaction of the fill. Fines also reduce permeability and hence the rate
of drainage. For these reasons, contracts governing the placement of hydraulic fill
70
generally ..contain a specification aimed at minimizing the amount of fines in the
. resulting fill. It is especially important to avoid ponding of water where fines might
settle out to form soft pockets or layers. Such specifications are, of course,
meaningful only when the borrow material contains just a modest amount of fines.
Often the specifications for dredge fill soils are only a general statement of intent, as
exemplified in the following typical statement:
"The discharge of fill material within the fill area shall be generally all over the area,
rather than confined to a single range or run, so that a minimum of silty material
shall settle out or be trapped in layers and pockets. In general, the filling operation
shall be carried on so that the free silt and mud shall be carried out of the area withthe waste water."
Sometimes a specification will contain a restriction upon the lift height, i.e., the
height of mound formed at a discharge point. A high lift height means that soil is
being carried a greater distance before deposition, and such a situation increases the
likelihood of deposition of fines or formations of ponds. For example, the maximum
permissible lift height for hydraulic filling at Newark Airport was 7 ft (Information
supplied by the New York P0l1 Authority), while the limit was 15 ft for underwater
filling at the Hampton Roads crossing (Steuerman and Murphy, 1957).
The quality of these soils as dredged material is graded on the basis of fine content
(i.e., percent passing no. 200 sieve or 0.075 mm sieve opening) as described in Table3.2.
Table 3.2 Quality of dredge fill materials.
Quality . Fine Content (Passing # 200 sieve)Very good <2%
Good 2%- 5%
Moderate 5% -10%
Fair 10% - 15%
Unsuitable >15%
71
72
OJ 0.01DIAMETER 'N liM
SAND SILTN[DIUN FINE COARSE "EDIUM
'0
90
lilTCLASSIFICATION
'DO
•...80x'"W 10J:
~ 60
:i~oz;;: 40
!r .tJ;,QII:
~ 20
Some soil samples had been collected from river bank river side and char of river
(i.e., Meghna and Kamrangirchar) that are used for filling low lands. Grain size
distributions of the soils have been presented in Figure 3.3. From the figure, it is seen
that in all cases the grain distributions fall out of the range of suitable soil for
hydraulic fill. Characteristics of the source materials have been presented in Table
3.3. In Table 3.3, FM is fineness modulus, Oso is mean grain size, 010 is effective
grain size, Fe is fines content (% passing No. 200 sieve). From this table, it is seen
that FM varies between 0.45 and 0.75, Oso ranges from 0.145 to 0.200 mm; fines
content varies between 0 to 15%, suitability as filling material is in most cases
moderate, in some cases fair and good.
Figure 3.2 Permissible range of grain sizes for hydraulic fill to be used for landfilling (Whitman, 1970)
3.5 CHARCTERIRISTCS OF SOURCE MATERIAL
Where there is a choice of borrow materials, specifications should limit the permissible
range of grain sizes in the borrow material or in the fill. Figure 3.2 (Whitman, 1970)
shows the permissible range of grain sizes for the hydraulic fill specified for Newark
Airport, which is normaily used for important structures.
73
0.01
-+-5.1-<il- 5-2--{]- S.3-+-5.4-;c- s.s
IParticle Size (mm)
Suitable range forhydraulic fill
100
80
•... 60(l)
<::<::~~ 40
20
010
Figure 3.3 Grain size distributions of samples collected from river banks and char.
Sample FM Dso DIO % of fines Suitability as fill soil
Designation (mm) (mm)
S.I 0.45 0.170 0.075 10.0 Moderate
S.2 0.33 0.145 . 15.0 Fair
S.3 0.63 0.185 0.080 6.0 Moderate
SA 0.60 0.170 0.081 7.0 Moderate
S.5 0.60 0.180 0.080 5.0 Moderate
Twenty one samples were collected from the river bed of Turag, Buriganga,
Dhaleshwari, Sitalakhya and Meghna. Grain size distributions of the samples have
been presented in Figure 3.4.
Table 3.3 Characteristics of soil samples collected from different sources
Similar study was conducted by BUET team (BRTC, 2005) for determining the
characteristics of source materials. Disturbed samples were collected from five river
beds during dredging operations and tested at the Geotechnical Engineering
Laboratory of BUET. The test results are described in the following.
0.010.1
Paticle size (mm)
I
Surce materialRiver bed:Turag, B uri!?,mgaDhaleswari Shitalakhya, Megjma(21 Samples)
74
40
20
80
60
100
Figure 3.4 Grain size distributions of samples collected from river bed.
River bad FM Dso Cu % Fines Suitability as fill
(mm) soil
Turag 0.60-0.70 0.17-0.19 2.22-2.64 2.4-9.4 Moderate-Good
Buriganga 0.48-0.94 0.15-0.20 1.83-2.63 2.0-10.0 Moderate-Good
Dhaleswari 0.03-0.64 0.08-0.18 2.00-2.50 5.2-33.9 Fair-Unsuitable
Sitalakhya 0.05-0.40 0.11-0.14 - 13.3-45.3 Fair-Unsuitable
Meghna 0.04-0.12 0.10-0.11 - 15.5-26.1 Unsuitable
Table 3.4 Grain size properties of soil samples collected during from river sources
A summary of the test results are presented in the Table 3.4. In Table 3.4, fineness
modulus (FM), mean grain size (Dso), uniformity coefficient (Cu), percent fines (Fe)
and suitability as fill soil have been presented. Fineness modulus (FM) varies
between 0.03 to 0.94, mean grain size (Dso) varies between 0.10 to 0.20, uniformity
coefficient (Cu) varies between 1.83 to 2.64, percent fines (Fe) varies between 2.0 to
45.3 and suitability varies between unsuitability to good.
Figure 3.5 Grain size distributions of samples collected from river banks and char.
0.01
0.00010.001
0.11Particle size (mm)
Surce materialRiver bank:Balughat, Katpatty,Dhaleswari Char,Kholamura GhatPurangonj Nagar(18 Samples)
Surce material20 River bank:Balughat, Katpatly,
haleswari Char,Kholamura GhatPurangonj Nagar
o (II Sample
10 1 0.1 0.01
Paric1e size (mm)
75
80
100
100
80
•... 60.,.S~~ 40
20
010
~ 60.S~~ 40
Twenty n;ne samples were collected from the river bank and char of Balughat,
Katpatty, Dhaleshwari Char, Kholamura Ghat, and Puranganj Nagar. Grain size
distributions of eleven samples have been presented in Figure 3.5 and grain size
distributions of other eighteen samples have been presented in Figure 3.6.
Figure 3.6 Grain size distributions of samples collected from river banks and char.
A summary of the test results are presented in the Table 3.5. In Table 3.5, fineness
modulus (FM), mean grain sizes (Dso), uniformity coefficient (Cu), percent fines (Fc)
and suitability as fill soil have been presented.
Table 3.5 Grain size properties of soil samples collected from various river banks
River bank Depth FM Dso Cu % Fines Suitability as
(m) (mm) fill soil
Balughat 4.5-7.5 0.01- 0.012- 11.33- 87.0-94.0 Unsuitable
0.015 0.015 14.29
10.0- 0.022- 0.025- 8.0- 73.0-85.0 Unsuitable
13.5 0.026 0.030 21.0
18.0 0.36- 0.13- - 12.5-13.8 Fair
0.39 0.13
Dhaleshawar 3.0-7.0 0.004- 0.022- 6.36- 53.0- Unsuitable
Char 0.007 0.071 10.50 950.0
10.0- 0.19- 0.10- 2.5- 9.2-31.0 Unsuitable-
17.0 0.91 0.20 2.63 moderate
Katpatty 6.0-13.0 0.28- 0.12- 3.50 7.3-17.2 Unsuitable-
1.21 0.25 moderate
Kholamura 7.0-7.5 0.003- 0.01 8- 6.44- 84-94 Unsuitable
Ghat 0.013 0.026 7.33
12.0- 0.32- 0.12- - 12.8-17.2 Unsuitable-
16.0 0.65 0.18 Fair
Purangonj 7.0-9.5 0.004- 0.027- 5.25- 82.0-92.0 Unsuitable
Nagar 0.02 0.036 7.80
13.0- 0.16- 0.10- - 23.4-28.9 Unsuitable
15.0 0.18 0.10
Fineness modulus (FM), of the samples collected from Balughat from depth of4.5 to
13.5 m varies between 0.01 to 0.026, mean grain size (Dso) varies between 0.012 to
0.03, uniformity coefficient (Cu) varies between 8.0 to 21.0, percent fines (Fc) varies
between 73.0 to 94.0 %. All the samples are unsuitable according to the suitability as
76I
fill soil. Fineness modulus (FM), of the samples collected from Balughat from depth
of 18.0 m varies between 0.36 to 0.39, mean grain size (Dso) varies between 0.13 to
0.13, percent fines (Fe) varies between 12.5 to 13.8 %. All the samples are fair
according to the suitability as fill soil. 1t is seen that the samples collected from
lower depth have very high fines content.
Fineness modulus (FM), of the samples collected from Dhaleshawri Char from depth
of 3.0 to 7.0 m varies between 0.004 to 0.007, mean grain size (Dso) varies between
0.022 to 0.071, uniformity coefficient (Cu) varies between 6.36 to 10.5, percent fines
(Fe) varies between 53.0 to 95.0 %. All the samples are unsuitable according to the
suitability as fill soil. Fineness modulus (FM), of the samples collected from
Dhaleshawri from depth of 10.0 to 17.0 m varies between 0.19 to 0.91, mean grain
size (Dso) varies between 0.10 to 0.20, uniformity coefficient (Cu) varies between 2.5
to 2.63, percent fines (Fe) varies between 9.2 to 31.0 %. All the samples are
unsuitable to fair according to the suitability as fill soil. 1t is seen that the samples
collected from lower depth have very high fines content.
Fineness modulus (FM) of the samples collected from Katpatty from depth of 6.0 to
13.0 m varies between 0.28 to 1.21, mean grain size (Dso) varies between 0.12 to
0.25, uniformity coefficient (Cu) varies between 0 to 3.5, percent fines (Fe) varies
between 7.3 to 17.2 %. All the samples are unsuitable to fair according to the
suitability as fill soil.
Fineness modulus (FM), of the samples collected from Kholamura Ghat from depth
of7.0 to 7.5 m varies between 0.003 to 0.013, mean grain size (Dso) varies between
0.018 to 0.026, uniformity coefficient (Cu) varies between 6.44 to 7.33, percent fines
(Fe) varies between 84.0 to 94.0 %. All the samples are unsuitable according to the
suitability as fill soil. Fineness modulus (FM), of the samples collected from
Kholamura Ghat from depth of 12.0 to 16.0 m varies between 0.32 to 0.65, mean
grain size (Dso) varies between 0.12 to 0.18, uniformity coefficient (Cu) varies
between 0 to 0, percent fines (Fe) varies between 12.8 to 17.2 %. All the samples are
77
unsuitable to fair according to the suitability as fill soil. It is seen that the samples
collected from lower depth have very high fines content.
Fineness modulus (FM), of the samples collected from Puranganj Nagar from depth
of 7.0 to 9.5 m varies between 0.004 to 0.02, mean grain size (Dso) varies between
0.027 to 0.036, uniformity coefficient (Cu) varies between 5.25 to 7.80, percent fines
(Fe) varies between 82.0 to 92.0 %. All the samples are unsuitable according to the
suitability as fill soil. Fineness. modulus (FM), of the samples collected from
Puranganj Nagar from depth of 13.0 to 15.0 m varies between 0.16 to 0.18, mean
grain size (Dso) varies between 0.10 to 0.10, uniformity coefficient (Cu) varies
between 0 to 0, percent fines (Fe) varies between 23.4 to 28.9 %. All the samples are
unsuitable to fair according to the suitability as fill soil. It is seen that the samples
collected from lower depth have very high fines content.
It can be concluded that most of the sources material has very high fines content
which is greater than 5 %. Soil containing fines 5 to 15 % can be selected for
developing the low lands. If the lands are developed with high fines content, it will
cause problem for ground improvement.
3.6 FILLING PROCEDURE
In hydraulic filling, soil suspended m water is pumped through a pipe and the
mixture discharged upon the surface being filled. This type of filling is used in many
places in the world. Figure 3.7 shows such discharge at pipe head (Whitman, 1970).
Typically, the ratio of volume of solid particles to volume of sluicing water is about
1 to 6 or I to 7. As the suspension flows away from the discharge point, the larger
soil particles settle out almost immediately and thus a mound form about the point of
discharge and grow in height. The water and soil fines flow away over the surface of
this mound. The slope of the mound is determined by the initial strength of the fill
and the distance that the water can carry soil particles before they settle. It ranges
from about 3: 1 for gravely fills to 50: I for weak cohesive fills.
78
In jobs where soil is dredged from a nearby channel or whenever borrows material is
a submerged soil near the site, the soil-water suspension generally is dredged and
pumped to the site in a single continuous operation. In other jobs, especially when a
specially selected borrow area lies at considerable distance from the site, the soil will
first be pumped into barges which are tOwed to the site, and then pumped from the
barges to the placement area. In some jobs, such as construction of small hydraulic
fill dams, borrow material may be trucked to the site, mixed with water in a hopper
box and pumped onto the placement area.
It has been mentioned that the presence of fines in a hydraulic fill means greater
compressibility together with greater difficulty in compaction of the fill. Fines also
reduce permeability and hence the rate of drainage. For these reasons, contracts
governing the placement of hydraulic fill generally contain a specification aimed at
minimizing the amount of fines in the resulting fill. It is especially important to avoid
ponding of water where fines might settle out to form soft pockets or layers.
Figure 3.8 depicts the filling procedure of low lands using method No. (3). In this
figure, it is seen that a boat or barge brings dredge material from remote places.
This dredge material is made slurry by mixing water. After that this slurry is
discharged to the site through pipes by pumping.
Figure 3.7 Discharge at pipe head (U.S. Army Corps of Engineers).
79
Arrangement to make slurry
80
Discharge of slurry to the site
Figure 3.8 Filling of lowlands using hydraulic fill.
Pumping of slurry from barge to site-!,.,.
,,'.
A boat with dredged material',1,' .
"~,-.~~
":' ..,',.
Figure 3.9 describes the distribution of particles from mouth point of pipe to
outwards. Due to gravity the coarser particles fall near the mouth point and the finer
particles faII to farther distance. As a result, segregation of particles occurs.
In view of above, the following procedure may be tried to obtain a fill of uniformdensity with adequate bearing capacity for structures:
a) The height of mound fanned at the discharge point should not exceed
5 ft. The water running away should not carry any soil beyond a
distance of 30-ft. Care should be exercised to avoid ponding of water
where fines might settle out to form soft pockets. If any such soft
pocket is found, drainage points need to be installed to improve the
soil density by de-watering or other ground improvement techniques.
DEVELOPMENT
Mouth Point
LANDRATIONAL
81
c) If necessary a trial procedure can be performed to achieve a relative
density of 70%. During field application if such density is not
achieved, ground improvement should be applied.
b) It is advisable to start filling operation by placing the discharge point
at the lowest surface within the filling area. Once an area is filled to a
pre-determined elevation, the discharge point may be moved to the
lowest point in the next filling area.
PROPOSAL FORPROCEDURE
Figure 3.9 Particle distributions after discharge to filling sites (not in scale).
3.7
However, to develop a rational method more investigations and study in thelaboratory and field are necessary based on the above mentioned discussion.
Investigations can be made by pumping the materials through vertical pipe. It mayimprove the distributions of the particles.
3.8 SUMMARY
This chapter deals with the development of the reclaimed areas' in and around
Dhaka City. The following conclusions can be drawn from the current study:
• Many reclaimed areas are being developed in and around Dhaka City. Main
reclaimed areas have been marked on the Dhaka City Map.
• Soil is collected from beds and banks of rivers such as Turag, Buriganga,
Dhaleshwari, Sitalakhya and Meghna.
• Characteristics of the source materials have been determined from survey of
source materials. About 53 samples were collected from different sources. The
fineness modulus, mean grain size, fines content varies between 0.003 to 0.94,
0.012 to 0.25 mm and 2.0 to 95 %, respectively. But soils contenting 5 to 15 %
is suggested for lowland development.
• There are four methods in practice to develop these areas. Generally, soil is
collected from riverbeds by cutter-suction dredging into a barge, which is
carried to the nearest river site. Soil is then pumped through pipes in a slurry
form after mixing with water, and transferred to the point of deposition.
However, in this method segregation of particles occurs.
• A proposal has been presented for the proper reclamation of reclaimed sites.
The sites should be filled up in such a way that the relative density should be
greater or equal to 70%. If the 70% relative density is not achieved, the site
should be improved by ground improvement techniques. More investigations
are necessary to develop a proper reclamation procedure.
82
Chapter Four
SUB-SOIL CHARACTERISTICSOF RECLAIMED AREAS IN DHAK CITY
4.1 GENERAL
The main objective of this research is to determine the sub-soil characteristics and
the liquefaction potential of selected reclaimed areas of Dhaka city. Standard
Penetration Test is widely used for the determination of liquefaction potential.
Sixteen borings were conducted at different reclaimed sites of Dhaka city. Huge
numbers of boring data are necessary for the analysis and clarification about sub-
soil characteristics. Many other bore hole data were collected from different
government and non-government agencies. Disturbed and undisturbed samples
were collected during SPT tests and tests were conducted on the collected samples.
Sub-soil characteristics have been determined based on the borehole data conducted
in this study and collected from other agencies. This Chapter presents the sub-soil
characteristics of selected reclaimed areas in Dhaka city.
4.2 SELECTED RECLAIMED AREAS
Dhaka, the largest city and at the same time the capital of Bangladesh enjoys a
distinct primacy in the national and regional urban hierarchy. The forecast of DMDP
(1995) anticipates a doubling of population over 25 years and an average annual
growth rate of 3.1%. High population increase demands rapid expansion of Dhaka
City. But unfortunately most of the areas of the Dhaka City have already been
occupied. As a result, different new areas are being developed by both government
and private agencies. There are many reclaimed areas in and around Dhaka City e.g.,
Uttara Residential Model Town (3rd Phase), Purbachal New Model Town,
Bashundhara, Mirpur DOI-lS, Jamuna City, Modumoti Model Town, Rupayan,
Nikunja, Keraniganj, Kamrangirchar, Banshri, Banani old DOHS, Pink city,
Shadesh, Banorupa Residential Project etc. However, Uttara Residential Model
Town (3rd Phase), Purbachal New Model Town, Bashundhara, Mirpur DOI-lS,
83
84
4.3 FIELD AND LABORATORY INVESTIGATIONS
(4.1)x r dmax
YdD = Yj - Ydmin
rYdmax - Ydmin
Relative density, Dr has been calculated as indicated in equation (4.1).
Banani old DOHS, Banasree and Keraniganj are the selected reclaimed areas in
and around Dhaka City for this study.
Mainly two types of investigations were conducted to determine the in-situ soil
conditions. These are - Field density test and Standard Penetration Test (SPT).
4.3.1 Field Density Test
Field density tests were conducted in Purbachal New Model Town and Uttara Model
Town (Third Phase) at arbitrarily selected 61 points. However, a few of the field test
data have been collected from Bureau of Research Testing and Consultation, BUET.
Field density tests have been conducted by Sand Cone Method (as per ASTM
DI556). Laboratory maximum and minimum density were determined according to
ASTM D 4253 and ASTM D 4254, respectively.
where, Yf is density of the soil in its natural state (field value), Ydmax is densest value
of unit weight obtained in the laboratory and Ydmin is loosest value of unit weight
obtained in the laboratory
Table 4.1 shows the relative density (Dr) description. Five classes based on Dr value
has been presented in the Table.
Table 4.1 Relative density (Dr) description
Range of Dr Description
0.00-0.15 Very Loose
0.15-0.35 Loose
0.35-0.65 Medium
0.65-0.85 Dense
0.85-1.00 Very dense
4.3.2 Standard Penetration Test
Standard Penetration Test has been conducted in different reclaimed areas in and
around Dhaka City. Standard Penetration Test is widely used for the detennination
of liquefaction potential. However, because of their inherent variability, sensitivity
to test procedure, and uncertainty, SPT N-values have the potential to provide
misleading assessments of liquefaction hazard, if the tests are not performed
carefully. To utilize SPT test results to estimate liquefaction potential test was
conducted according to ASTM D 1586 (ASTM, 1998) in order to avoid, or at least
reduce, some of the major sources of error. The Standard Penetration Test is
recommended mainly for granular soils but has been used in cohesive soils also.
Field investigations have been conducted to determine the sub-soil characteristics
of reclaimed areas. The main objectives are as below:
(a) Boring and recording of soil stratification
(b) Sampling (both disturbed and undisturbed)
(c) Execution of Standard Penetration Test (SPT)
(d) Recording of ground water table
Main features of the SPT test have been presented below:
85
Procedure of SPT test
The Standard Penetration Test uses a 50 millimeter diameter pipe (split spoon)
driven with a 63.5 kilS'gram hammer at a drop of 750 millimeters. The test is
described in ASTM D1586. A short procedure of SPT N-value test is described in
Table 4.2.
Table 4.2 Recommended SPT procedure (ASTM D1586)
Equipments Short procedure
Borehole size 65 mm < Diameter < I 15 mm
Borehole support Casing for 3m length and drilling mud
Drilling • Wash boring• Side discharge bit rotary boring• Side or upward discharge bit clean bottom of
bore hole
Drill rods A or AW for depths of less than IS m N or NW for
.greater depths
Sampler Standard O.D. 51 mm +/- I mm, LD. 35 mm +/- I mm
and length> 457 mm
Penetration Record number of blows for each 150 mm; N - number
resistance of blows from ISO to 450 mm penetration
Blow count rate 30 to 40 blows per minute.
Drilling method
The borehole should be made by mud rotary techniques using a side or upward
discharge bit. Hollow-stem-auger techniques generally are not recommended,
because unless extreme care is taken, disturbance and heave in the hole is common.
However, if a plug is used during drilling to keep the soils from heaving into the
augers and drilling fluid is kept in the hole when below the water table (particularly
when extracting the sampler and rods), hollow-stern techniques may be used. If
water is used as the fluid in a hollow-stem hole, and it becomes difficult to keep the
fluid in the hole or to keep the hole stable, it may be necessary to use a drilling fluid
86
(consisting of mud or polymers). With either technique, there is a need for care when
cleaning out the bottom of the borehole to avoid disturbance. Prior to extracting the
drill string or auger plug for each SPT test, the driller should note the depth of the
drill hole and upon lowering of the sampler to the bottom of the hole, the depth
should be carefully checked to confirm that no caving of the walls or heaving of the
bottom of the hole has occurred.
Hole diameter
Preferably, the borehole should not exceed I 15 mm in diameter, because the
associated stress relief can reduce the measured N-value in some sands. However,
if larger diameter holes are used, the factors listed in Table 4.3 can be used to
adjust the N-values for them. When drilling with hollow-stem augers, the inside
diameter of the augers is used for the borehole diameter in order to determine the
correction factors provided in Table 4.3.
Drive-rod length
The energy delivered to the SPT can be very low for an SPT performed above a
depth of about 10m due to rapid reflection of the compression wave in the rod. The
energy reaching the sampler can also become reduced for an SPT below a depth of
about 30 m due to energy losses and the large mass of the drill rods. Correction
factors for those conditions are listed in Table 4.3i."
Sampler type
If the SPT sampler has been designed to hold a liner, it is important to ensure that a
liner is installed, because a correction of up to about 20% may apply if a liner is not
used. In some cases, it may be necessary to alternate samplers in a boring between
the SPT sampler and a larger-diameter ring/liner sampler. The ring/liner samples
are normally obtained to provide materials for normal geotechnical testing.
Although the use of a plastic sample catcher may have a slight influence on the
SPT N-values, that influence is thought to be insignificant and is commonly
neglected.
87
88
(4.3)
(4.2)
Down-hole hammers, raised and lowered using a cable wire-line, should not be
used unless adequately designed and documented correlation studies have -been
performed with the specific equipment being used. Even then, the use of such
equipment typically results in highly variable results, thereby making their results
questionable.
One of the single most important factors affecting SPT results is the energy
delivered to the SPT sampler (Table 4.4). This is normally expressed in terms of
the rod energy ratio (ER). An energy ratio of 60% has generally been accepted as
the reference value. The value of ER (%) delivered by a particular SPT setup
depends primarily on the type of hammer/anvil system and, the method of hammer
release. Values of the correction factor used to modify the SPT results to 60%
energy (ER/60) can vary from 0.3 to 1.6, corresponding to field values of ER of
20% to 100%. Table 4.4 provides guidance for summary of rod energy ratios
provide specific recommendations for energy correction factors.
Energy delivery
Standard Rod energy ratio = 60 %
where, nd is dynamic efficiency depends on anvil weight (0.87-0.6); ERy is Velocity
energy ratio
Spatia/frequency of tests
SPT tests should be performed at intervals that are consistent with the geotechnical
needs of the project. At a minimum, for liqucfaction analyscs, SPT tcsts should be
performed at vertical intervals of no more than 1.5 m or at significant stratigraphic
changes, whichever results in more tests. The horizontal spacing between borings
will depend on the project needs.
Some other factors that affect the SPT N-value have been presented in Table 4.5.
Table 4.3 Borehole, sampler and correction factors (Skempton, 1986)
Factor Equipment Variable Symbol Correction value
Rod length 3mto4m CR 0.75
4 m to 6m 0.85
6mto10m 0.95
>10m 1.00
Sampling Standard Sampler Cs 1.00
method U.S. Sampler without 1.20
liners
Borehole 65 mm to 115mm CB 1.00
Diameter 150 mm 1.05
200mm 1.15
Table 4.4 SPT hammer efficiencies (Clayton, 1990)
Country Hammer Release ERy(%) ERy/60
Japan Donut Tombi 78 1.30
Donut 2 turns of rope 65 1.10
China Pilcon type Trip 60 1.00
Donut Manual 55 0.90
USA Safety 2 turns of rope 55 0.90
Donut 2 turns of rope 45 0.75
UK PiIcon, Dando Trip 60 1.00
Old standard 2 turns of rope 50 0.80
4.3.3 LABORATORY TESTS
Disturbed and undisturbed samples were collected during SPT tests collected
samples were tested at Geotechnical Engineering Laboratory of BUET. List oftests
conducted are presented in Table 4.6. These tests were performed according to the
89
procedure specified by ASTM (American Society for Testing Material) standard.
Laboratory tests that were conducted are specific gravity, grain size analysis,
unconfined compression test and laboratory maximum and minimum densities. The
details of the test procedures are available at the ASTM standards.
Table 4.5 Factors affecting the SPT (Kulhawy and Mayne, 1990)
Cause Effects Influence onSPT N-value .
Inadequate cleaning of SPT is not made in original Increaseshole in- situ soil. Therefore, spoils
may become trapped 111
sampler and be compressed assampler IS driven, reducingrecovery
Failure to maintain Bottom of borehole may Decreasesadequate head of water in become "quick" and soil mayborehole sluice into the holeCareless measure of Hammer energy varies Increaseshammer drop
Hammer weight Hammer energy varies Increases orinaccurate decreasesHammer strikes drill rod Hammer energy reduced Increasescollar eccentrically
Lack of hammer free fall Hammer energy reduced Increasesbecause of ungreasedsheaves or new stiff rope
Sampler driven above Sampler driven in disturbed, Increases greatlybottom of casing artificially densified soilCareless blow count Inaccurate results Increases or
decreasesUse of non-standard Corrections with standard Increases orsampler sampler not valid decreasesCoarse gravel or cobbles Sampler becomes clogged or Increasesin soil impeded
90
Table 4.6 List of tests conducted
Name of test ASTM Designation
Specific gravity ASTMD 854
Grain size analysis ASTMD422
Hydrometer analysis ASTM Dll40 & ASTM C136
Unconfined compression tcst ASTMD2166
Laboratory maximum density ASTMD4253
Laboratory minimum density ASTMD4254
4.4 SUB-SOIL CHARACTERISTICS OF RECLAIMED AREAS
Sub-soil characteristics of the selected reclaimed areas of Dhaka city have been
determined based on filed and laboratory density tests, Standard penetration tests and
laboratory tests. The sub-soil characteristics of the areas are described below.
4.4.1 Sub-Soil Characteristics of Bashundhara
The area Bashundhara is situated in Dhaka. There are twelve blocks in the project
area. Five borings were conducted at the site in the present study. Fifty three (53)
bore hole data were. collected from Bashundhara. Approximate locations of the
boreholes are marked on the map of Bashundhara as shown in Figure 4.1.
91
eBlI.I!.l•UIl.OI
-.,:,uoiii
::r:.,:,u •.3 UIl.()2
CO
Rajuk's 300' Wide Road
The field and laboratory test results of the five bore holes that are conducted in this
study have been presented in Table B-1 to B-5 in Appendix B. Variation of SPT N-
value with depth of the five bore holes are presented in Figure 4.3a. It is seen that
water table exists at about 2.0 m from the existing ground level (EGL). The variation
of mean grain size (Dso) with depth for the five boreholes also have been presented
in Figure 4.3b.
92
Figure 4.1 Approximate locations of bore holes at Bashundhara site.
From Figure 4.3a, it is seen that N-value varies from I to 10 up to 5 m depth from
EGL. The SPT-N-value varies from I to 15 for the depth from 5 to 10m. The SPT
N-value varies from 3 to 27 for the depth from 10 to 17m. Below this level, SPT N-
value varies from 10 to 45. From Figure 4.3b, mean grain size varies from 0.10 to
0.40 mm for the depth from 0 to 5 m. For the depth from 5 to 20 m the mean size
was very small for three samples i.e. 0.02 mm. For one location the mean size was
almost similar for the whole depth i.e., 0.15 mm. The soil type is silty fine sand for
the depth from EGL to 5 m. For the next 5 to 10m depth the soil is clayey soil.
The field and laboratory test results of the twenty bore holes of the block A, Band F
that are collected in this study have been presented in Table B-6 to B-25 in Appendix
B. Variation of SPT N-value with depth of the twenty bore holes are presented in
Figure 4.4a. It is seen that water table exits at about 2.5 m from the existing ground
level (EGL). The variation of mean grain size (Dso) with depth for the twenty
boreholes also have been presented in Figure 4.4b. It is to be noted that mean grain
size of the samples could not be determined due to the shortage of samples.
From Figure 4.4a, it is seen that N-value varies from I to 10 up to 5 m depth from
EGL. The SPT-N-value varies from I to 20 for the depth from 5 to 10 m. The SPT
N-value varies from 10 to 30 for the depth from 10 to 15. Below this level, SPT N-
value varies from 20 to 50. From Figure 4.4b, mean size varies from 0.02 to 0.25 mm
for thc depth from. 0 to 20 m. Mean grain size are almost similar i.e. 0.02 mm. The
soil type is sandy silt for the depth from EGL to 5 m. For the next 5 to 27 m depth
the soil is clayey soil.
The field and laboratory test results of other thirteen bore holes of block I, G and
tenement building that are collected in this study have been presented in Table B-26
to B-37 and B-50 in Appendix B. Variation of SPT N-value with depth of the
thirteen bore holes are presented in Figure 4.5a. It is seen that water table exits at
about 1.0 m from the existing ground level (EGL). The variation of mean grain size
(Dso) with depth for the thirteen boreholes also have been presented in Figure 4.5b.
From Figure 4.5a, it is seen that N-value varies from I to 20 up to 13 m depth from
EGL. Below this level SPT N-value varies from 8 to 50. Mean grain size varies
from 0.01 to 0.35 mm for the dcpth from 0 to 13 m. From Figure 4.5b, mcan grain
size varies from 0.01 to 0.18 mm for the depth from 13 to 18 m. For the depth from
18 to 27.5 m the mean size was very small for thIee locations i.e. 0.025 mm. The soil
type is fine sand for the depth from EGL to 13 m. For the next 13 to 27 m depth the
soil is sandy silt and silty clay.
The field and laboratory test results of other twenty bore holes that are collected in
this study have been presented in Table B-38 to B-49 and B-51 to B-58 in Appendix
B. Variation of SPT N-value with depth of the twenty bore holes are presented in
Figure 4.6a. It is seen that water table exits at about 2.0 m from the existing ground
93
level (EGL). The variation of mean grain size (Dso) with depth for the twenty
boreholes also have been presented in Figure 4.6b.
From Figure 4.6a, it is seen that N-value varies from I to 10 up to 10m depth from
EGL. Below this level SPT N-value varies from 2 to 48. Mean grain size varies
from 0.01 to 0.35 mm for the depth from 0 to 5 m. From Figure 4.6b, mean grain size
varies from 0.01 to 0.16 mm for the depth from 5 to 10 m. For the depth from 10 to
25 m the mean size was very small for three samples i.e. 0.025 mm. The soil type is
fine sand and silty clay for the depth from EGL to II m. For the next II to 25 m
.depth the soil is clayey silt and silty clay.
There were clay layers at 5.50 m depth in BH-3, at 7.0 m and 9.75 m depth at BH-5,
at 4 and 7.0 m depth. Unconfined compressive tests are conducted for the sanlples.
Stress versus strain graph for the sample collected for BH-4 is shown in Figure 4.2
for unconfined tests result. Test results of unconfined compressive test have been
presented in Table 4.7. In the table, w is water content, Ydl)" is dry density, qu is
unconfined compressive strength, and Ef is failure strain. It is seen that dry unit
weight and the moisture content of the samples varies between 23.6 to 29.4% and
13.96 to 15.42 kN/mJ, respectively. Unconfined compressive strength varies between
43.6 and 581.8 kN/mJ. Failure strain was 15% in most cases .
•Table 4.7 Unconfined compression test results of samples collected from
Bashundhara area
Borehole Depth Sample w Ydl)" qu EfNo. (m) No. (%) (kN/mJ) (kN/m2
) (%)BH-3 5.50 UD-I-I 28.1 15.60 259.0 15.0
UD-I-2 26.7 14.40 94.6 15.0BH-4 7.00 UD-I-I 27.1 15.17 138.4 14.0
UD-1-2 26.6 15.42 191.5 15.0BH-4 9.75 UD-2-1 25.5 16.63 400.2 10.0
UD-2-2 22.6 16.80 581.8 15.0BH-5 4.00 UD-1-1 28.0 14.07 174.6 15.0BH-5 7.00 UD-I-I 23.6 15.58 I 19.3 15.0
UD-I-2 29.4 13.96 43.6 15.0
94
0.5
15
Bashundhara
Mean grain size, 050 (mOl)
0.1 0.2 0.3 0.4
(b)
oo
25
Location: BashundharaBore Hole No.: BH-4Depth: 7.0 m
10
Strain (%)5
50
-tl- ,W ~ 27.1 %, y ~ 15.17 kN/m
d'Y-.- W = 26.6 %, Y = 15.42 kN/m'
d'Y
GWT
aa
50
Clayey soil
95
30 40
100
150
200
250
300
Bashundhara
20
Silty fine sand
---- BH-01-11-
---- BH-03-*-BH-04-*-BH-05
Figure 4.2 Stress vs strain of BH NO.4 at Bashundhara site.
UnCOlTccted-N Value
10
(a)
oo
5
25
20
10 ]: 10]: .c.c 15.15. uu Silty clay 00
IS 15
Figure 4,.3 (a) Depth versus SPT N-value and (b) Depth versus Dso at Bashundhara
0.4
OJ
(b)
0.3
0.2
0.2
BashundharaBlock-A, B & F
0.1
0.1
Mean grain size, D (mm)50
(b)
Mean grain size, D 50 (mm)
5
20
25
20
30
50
40 50
WT
(al
40
GWT
30
30
ashundharaBloc -A & F
20
Sandy silt
20
Organic clay
Uncorrected N-value
10
Uncorrected N- Value
10
Clay soil
BashundharaBlock-I, G & Tent.6
(a)
5
oo
96
oo
5
30
20
25
20
25
30
~ 10-5
10E~-a .s" e-O 015 15
Figure 4.4 (a) Depth versus SPI N-value and (b) Depth versus D50 at Bashundhara
Figure 4.5 (a) Depth versus SPI N-value and (b) Depth versus Dso at Bashundhara
g 10 ~ 105--a .c15.
" "0 015 15
0.4
(b)
0.30.20.1
Mean grain size, D 50 (mm)
BashundharaTent. Build.-] & 7
5
oo
25
30
20
(a)
Uncorrected N-Yalue
10 20 30 40 50
BashundharaTent Build.-I & 7
oo
30
~ 10 ~ 105 5-5 -5iT 0-
"Cl Cl15 15
97
Figure 4.6 (a) Depth versus SPT N-value and (b) Depth versus Dso at Bashundhara
4.4.2 Sub-Soil Characteristics of Purbachal New Model Town
The area Purbachal New Model Town is situated in and around Dhaka City. There
are fifteen unions in the project area. Three borings are conducted at the site in the
present study. Approximate locations of the boreholes in marked on the map of
Purbachal New Model Town as shown in Figure 4.7.
Field density tests were conducted at arbitrarily selected 21 points at Pitolganj,
Purbachal New Model Town. Soil samples were collected during field density test
for grain size analysis and laboratory density tests. Grain size distribution of some
samples as shown in Figure 4.8. Moisture content, grain size distribution, field
density, laboratory maximum and minimum density test results at Pitolganj,
Purbachal New Model are presented in Table 4.8.
500 SOO 1000 Meiers15il"!-
Figure 4.7 Approximate location ofborc holes of Pur bacha I New Model Town.
In Table 4.8, Wn indicates the natural moisture content, FM is fineness modulus,
Fe is fines content (% passing no. 200 sieve), Yr is field density, Ydmin is minimum
density detennined at laboratory and Ydmax is maximum density determined at
laboratory. Sample depth was 0.15 to 1.0m. From Table 4.8, it is seen that
natural moisture content varies between 1.4 to 31.2 %, Fineness modulus (FM)
varies from 0.83 to 7.20, Fines content (% passing No. 200 sieve) varies from
0.22 to 5.6 %, and soil type in all cases is fine sand. Field density varies from
12.84 to 16.52 kN/m3, laboratory maximum and minimum density varies from
15.20 to 17.20 kN/m3 and 11.41 to 13.79 kN/m3, respectively. Relative density
determined for field, laboratory maximum and minimum densities varies
between 33 to 107 %. However, relative density (D,) of 15 samples out of 21
samples is less than 70 %.
98
100
80 I- ~~
-
g 60 I-
~~ 40 -
20 I- Pitolganj, Purbachal !Depth = 1.0 m •0 , ,
10 I 0.1 0.01
Particle size (mm)
Figure 4.8 Grain size distribution of samples collected from Pitolganj, Purbachal
Table 4.8 Field and laboratory density test results of samples collected fromPitolganj, Purbachal
Sample Depth Wn % Yr Ydmin Ydmax 0,FM Soil type3 3 3ID (m) (%) fines (KN/m) (l"'::N/m ) (KN/m) (%)
PI (I) 0.150 4.40 0.83 5.60 Fine sand 14.98 12.78 16.53 65.0PI (2) 0.225 4.80 2.10 1.05 Fine sand 14.61 13.16 16.95 44.3P2(1) 0.150 1.40 2.70 0.94 Fine sand 14.78 12.81 16.35 61.6P2(2) 0.150 5.80 1.52 0.22 Fine sand 12.84 11.49 15.31 42.4P3(1) 0.150 4.70 6.10 1.00 Fine sand 15.31 13.16 16.95 62.8P3(2) 0.150 5.70 5.40 0.31 Fine sand 15.02 12.12 15.90 81.2P3(3) 0.150 3.90 3.60 0.99 Fine sand 15.31 13.16 16.95 62.8P4(1) 0.225 3.20 3.10 1.32 Fine sand 15.10 13.79 17.20 43.8P4(2) 0.225 4.30 6.20 0.69 Fine sand 14.47 12.71 16.62 51.7P4(3) 0.225 5.80 4.20 0.38 Fine sand 13.06 12.04 15.78 33.0P5(1 ) 0.150 4.30 5.10 0.80 Fine sand 14.82 12.78 16.53 60.7P5(2) 0.150 3.30 1.50 0.93 Fine sand 14.85 12.81 16.35 63.5P5(3) 0.150 2.90 2.40 1.13 Fine sand 15.27 13.47 17.11 55.4P5(4) 0.150 4.20 7.20 0.65 Fine sand 15.46 12.71 16.62 75.6P-I-I 1.000 22.00 0.56 11.0 Fine sand 15.25 12.11 15.94 85.8P-I-2 1.000 31.50 0.66 9.0 Fine sand 14.60 12.40 16.18 64.5P-2-1 1.000 30.70 0.45 22.0 Silty sand 15.03 11.91 16.05 80.3P-2-2 1.000 22.90 0.77 8.0 Fine sand 15.81 13.01 16.72 79.7P-4-1 1.000 21.50 0.42 12.0 Fine sand 16.52 12.18 16.15 107.0P-4-2 1.000 25.70 0.27 19.0 Silty sand 13.78 11.41 15.20 69.0P-4-3 1.000 20.80 0.76 11.0 Fine sand 16.07 13.14 17.00 80.2
99
100
0.010.1
Particle size (mm)
Brahmnkhali,PurbachalDepth= 1.0m
100
80
~ 60<l)c:~'J?, 40
20
010
Field density tests were conducted at arbitrarily selected 28 points at Brahmankhali,
Purbachal New Model Town. Soil samples were collected during field density test
for grain size analysis and laboratory density tests. Some typical grain size
distributions of samples are presented in Figure 4.9. Moisture content, grain size
distribution, field density, laboratory maximum and minimum density test results at
Brahmankhali, Purbachal New Model are presented in Table 4.9. Sample depth
varied between 0.15 to 1.0 m.
Figure 4.9 Grain size distribution of samples collected from Brahmankhali,Purbachal.
From Table 4.9, it is seen that natural moisture content varies between 3.1 to 30.4 %,
Fineness modulus (FM) varies between 0.15 to 1.45, Fines content (% passing no.
200 sieve) varies from 0.9 to 11.7 %. Soil type in all cases is fine sand. Field density
varies from 12.93 to 17.33 kN/m3, laboratory maximum and minimum density varies
between 11.43 to 17.20 kN/m3 and 11.49 to 16.92 kN/m3, respectively. Relative
density (Dr) of the samples varies from 29.0 to 103 %. However, 50 % samples had
relative density less than 70 %.
Table 4.9 Field and laboratory density test results of samples collected fromBrahmankhali, Purbachal
Sample Depth W" %of Yr 'Ydmin 'Yumax 0,FM Soil type
3 3 JID (m) (%) fines (KN/m) (KN/m ) (KN/m) (%)
Bl(l) 0.150 4.6 0.91 4.9 Fine sand 15.2 12.81 16.35 56.6
B 1(2) 0.225 3.2 1.45 0.9 Fine sand 15.77 13.51 16.95 70.6B2(l) 0.150 5.0 0.42 5.6 Fine sand 14.33 12.04 15.78 67.4
B2(2) 0.150 4.8 0.68 4.5 Fine sand 14.71 12.71 16.62 57.8B3(l) 0.150 5.3 0.67 5.3 Fine sand 14.70 12.71 16.62 57.5
B3(2) 0.150 5.8 0.42 6.3 Fine sand 13.61 12.04 15.78 48.8
B4(l) 0.225 14.0 0.82 1.0 Fine sand 15.08 12.78 16.53 67.2
B4(2) 0.225 11.9 0.40 3.0 Fine sand 12.93 12.04 15.78 29.0
B5(1) 0.150 6.3 0.70 4.2 Fine sand 15.60 12.71 16.62 78.7
B5(2) 0.150 9.1 0.48 6.1 Fine sand 14.58 12.04 15.78 73.5B6(l) 0.150 3.3 0.83 6.2 Fine sand 15.41 12.78 16.53 75.2B6(2) 0.150 5.2 0.63 8.0 Fine sand 15.82 12.71 16.62 83.6B7(l) 0.150 8.2 0.29 4.2 Fine sand 15.41 12.12 15.90 89.8
B7(2) 0.150 5.8 0.15 8.9 Fine sand 14.21 11.49 15.31 76.5B8(l) 0.150 4.1 0.68 4.7 Fine sand 16.16 12.71 16.62 91.4
B8(2) 0.150 7.3 0.43 11.7 Fine sand 14.09 12.04 15.78 61.4
B9(1 ) 0.150 3.1 1.28 4.4 Fine sand 15.71 13.79 17.20 61.6
B9(2) 0.150 3.5 1.13 5.0 Fine sand 14.21 13.47 17.11 24.5
B10(l) 0.150 3.6 1.16 3.2 Fine sand 15.99 13.47 17.11 74.1
BlO(2) 0.150 4.1 0.65 5.3 Fine sand 15.33 12.71 16.62 72.6
Bl1(l) 0.150 5.8 0.79 7.1 Fine sand 16.13 12.78 16.53 91.5
B 11(2) 0.150 6.8 0.21 8.8 Fine sand 13.54 11.49 15.31 60.7
B-2-1 1.000 13.1 0.58 8 Fine sand 15.44 16.20 12.42 95.4
B-2-2 1.000 23.0 0.60 19 Silty sand 16.13 15.62 11.51 103.3
B-3-1 1.000 27.2 0.67 8 Fine sand 15.24 16.21 12.39 94.0B-3-2 1.000 19.2 1.36 4 Fine sand 17.33 16.92 13.68 102.5
B-4-1 1.000 30.4 0.39 17 Silty sand 13.59 15.30 11.43 88.9
B-4-2 1.000 22.5 0.22 16 Silty sand 16.18 15.91 12.19 101.7
101
The field and laboratory test results of the three bore holes that were conducted in
this study have been presented in Table B-59 to B-61 in Appendix B. Variation of
SPT N-value with depth of the three bore holes are presented in Figure 4.IOa. It is
seen that water table exits at about 2.5 m from the existing ground level (EGL). The
variation of mean grain size (Dso) with depth for the three boreholes also have been
presented in Figure 4.1Ob. It is to be noted that mean grain size of all type samples
could not be determined due to the shortage of samples. If cases of missing data,
some values were assumed based on soil type to show the variation wills depth.
From Figure 4.IOa, it is seen that N-value varies from I to 10 up to 5 m depth from
EGL. The SPT-N-value varies from 2 to 20 for the depth from 5 to 10m. Below this
level, SPT N-value varies from 7 to 45. From Figure 4.IOb, mean grain size varies
from 0.02 to 0.32 mm for the depth from 0 to 5 m. Mean grain size varies from 0.02
to 0.18 mm for the depth from 5 to 10 m. For the depth from 10 to 20 m the mean
size was very small for three samples i.e. 0.10 to 0.15 mm. The soil type is silty fine
sand for the depth from EGL to 4.5 m. The soil type is clay for the depth from 4.5 to
7.5 m .For the next 7.5 to 20 m depth the soil is silty sand.
There were clay layer at 6.0 m depth in BH-2. Unconfined compressive tests were a
conducted for the sample. Test results of unconfined compressive test have been
presented in Table 4.10. In the table, w is water content, Ydry is dry density, q, is
unconfined compressive strength, and Ef is failure strain. Dry unit weight and
moisture content of the sample varies between 15.15 to 15.79 kN/mJ and 20.8 to
23.2%, respectively. Unconfined compressive strength varies between 106.8 to 161.0
kN/mJ. Failure strain varied between 5 to 15%
Table 4.10 Unconfined compression test results of samples collected fromPurbachal New Model Town
Borehole Depth Sample w Ydry q, EfNo. (m) No. (%) (kN/mJ) (kN/m2) (%)BH-2 6.0 UD-I-I 20.8 15.29 106.8 15.0
UD-I-2 23.2 15.15 161.0 5.0UD-I-3 22.7 15.79 133.9 11.0
102
Purbaehal NewModel Town
Mean grain size, 050 (mm)o 0.1 0.2 0.3 0.4o
5 I
25 (b)
20
Clay soil
Purbaehal NewModel Town
GWTSilty fine sand
Uncorrected N- Value
•
5
25 (a)
20
10 10~ gg.c .c15- 15-
"" CiCi15 15
Figure 4.10 (a) Depth versus SPT N-value and (b) Depth versus Dso at Purbachal
New Model Town
4.4.3 Sub-Soil Characteristics of Uttar a Model Towu (Third Phase)
Uttara Model Town (3'd phase) is located at the north-western corner of the city
corporation area having the Uttara Model Town (2nd phase) to the east and Mirpur to
south of the project area. The total project area is about 2010 acres and is entirely
within the western Dhaka flood protection embankment constructed on the east bank
of the Turag River.
103
The first phase of the Uttara Model Town Project was started in 1966 and finished in
1992. The second phase of the project was started immediately after the completion
of the first phase and its implementation was completed in 1998. The project is now
in its third phase encompassing the area described above. The area plan divides the
whole area into 4 sectors which are again subdivided into 40 neighborhoods. The
project is expected to accommodate more than four hundred thousand people in the
area.
@BH-l
BH-3
~
@BH-2
Dia Bari Village
BH-4
@BH.6
@
104
N
e3
Figure 4.11 Approximate locations of bore holes at Uttara Model Town (Thirdphase).
Six borings were conducted at the site in the present study. Approximate locations of
the boreholes are marked on the map of Uttar a Model Town (Third Phase) as shown
in Figure 4.11.
Field density tests were also conducted at arbitrarily selected 12 points at Dia Bari in
Uttara Model Town (Third Phase). Soil samples were collected during field density
105. ~
0.010.1Particle size (mm)
Location: Dia Bari, UttaraDepth: 0.30 - 1.75 mNo. of samples: 12
100
80
~ 60"<::~~ 400
20
010
test for grain size analysis and laboratory density tests. Some typical grain size
distribution of samples are presented in Figure 4.12. Moisture content, grain size
distribution, field density, laboratory maximum and minimum density test results at
Dia Bari in Uttara Model Town are presented in ,Table 4.11. Sample depth varies
0.30 to 1.75 m.
From Table 4.11, it is seen that natural moisture content varies between 3.7 to 28 %,
Fineness modulus (FM) varies from 0.33 to 0.75, Fines content (% passing no. 200
sieve) varies from 3.3 to 15.1%. Soil type in all cases is fine sand. Field density
varies from 14.66 to 17.54 kN/mJ, laboratory maximum and minimum density varies
from 15.44 to 16.50 kN/mJ and 11.43 to 12.43 kN/mJ, respectively. Relative density
(D,) of the samples varies between 51 to 82%. However, eight samples had relative
density less than 70 %.
Figure 4.12 Grain size distribution of samples collected from Uttara Model Town.
The field and laboratory test results of the six bore holes that were conducted in this
study have been presented in Table B-62 to B-67 in Appendix B. Variation of SPT
N-value with depth of the six bore holes are presented in Figure 4.13a. It is seen that
water table exits at about 2.0 m from the existing ground level (EGL). The variation
of mean grain size (Dso) with depth for the six boreholes also have been presented in
Figure 4.13b. It is to be noted that mean grain size of all samples could not be
determined due to the shortage of samples.
Table 4.11 Field and laboratory density test results of samples collected from DiaBari, Uttara
Sample Depth Wn FM F, Soil type rr Ydmax Ydmin D,ID (m) (%) (%) 3 ) )
(KN/m) (KN/rn ) (KN/m) (%)
S-I-1 1.00 5.3 0.64 3.7 Fine sand 15.48 15.76 12.32 74.1S-I-2 1.00 5.7 0.49 7.3 Fine sand 16.04 16.00 12.29 81.7S-3-1 1.00 6.2 0.59 5.6 Fine sand 15.88 16.02 12.21 77.1S-3-2 1.00 6.5 0.69 6.2 Fine sand 15.46 16.28 12.43 60.9S-5-1 1.50 6.5 0.75 4.6 Fine sand 16.42 16.50 12.53 77.7S-5-2 1.50 4.7 0.71 3.3 Fine sand 15.24 15.92 12.19 69.0S-7-1 1.50 8.2 0.45 9.5 . Fine sand 15.16 16.31 12.19 51.2S-7-2 1.00 5.3 0.56 4.2 Fine sand 15.00 15.68 12.03 66.4S-9-1 1.00 28.0 0.33 15.1 Silty sand. 17.54 15.44 11.43 63.7S-9-2 1.00 5.4 0.55 7.1 Fine sand 14.77 15.99 12.03 57.0S-11-1 0.30 3.7 0.62 5.4 Fine sand 14.66 16.02 12.11 58.8S-11-2 1.75 6.3 0.61 7.4 Fine sand 15.03 16.47 12.32 51.0
From Figure 4.13a, it is seen that N-value varies from I to 10 up to 10m depth from
EGL. The SPT-N-value varies from 2 to 18m for the depth from 10 to 15 m. Below
this level SPT N-value varies from 8 to 22. From Figure 4.13b, mean grain size
varies from 0.02 to 0.25 mm for the depth from 0 to 10m. Mean grain size varies
from 0.02 to 0.22 mm for the depth from 10 to 18 m. For two samples the mean grain
size was almost similar for the depth from 5 to 20 m i.e, 0.02 mm. The soil type is
silty fine sand for the depth from EGL to 4 m. The soil type is clayey silty and clay
soil for the depth from 4 to 14 m. For the next 14 to 20 m depth the soil is silty sand.
There was clay layer at 4.88 m depth in BH-3. Unconfined compression test were
conducted for the samples. Test results of unconfined compressive test have been
presented in Table 4.12. In the table, w is water content, Ydry is dry density, qu is
unconfined compressive strength, and €f is failure strain. Dry unit weight of the
samples varies between 18.15 to 18.39 kN/mJ. Unconfined compressive strength
varies between 477.9 to 588.0 kN/mJ.
106
Sf(%)14.012.0
qu(kN/m2
)
588.0477.9
Ydry(kN/m3)
18.1518.39
w(%)13.714. I
SampleNo.
UD-I-IUD-I-2
Depth(m)4.88
107
BoreholeNo.BH-4
Table 4.12 Unconfined compression test results of samples collected from UttaraModel Town
Uncorrected N- ValueMean grain size, D 50 (mm)0 5 10 15 20 25
0.20 00 o. I 0.3GWT
Fine silty sand
5 5
/10 10~
E gI~
~.c15. .c" 15.Cl "Cl15 15
~20 20
UttaraModel Town UttaraModelTown25 (a) (Third Phase)
25 (b) (Third Phase)
Figure 4.13 (a) Depth versus SPT N-value and (b) Depth versus D50 at Uttara ModelTown (Third Phase)
4.4.4 Sub-Soil Characteristics of Mirpur DOHS
The area is situated in Dhaka, total area of the project is 74.0 acres, and number of
plot is 693. Twenty three borehole wcre collected from private agencies for Mirpur
DOHS site. Approximate locations of the boreholes are marked on the map of
Mirpur DOHS as shown in Figure 4. I4.
The field and laboratory test results of the twenty three bore holes that were collected
in this study have been presented in Table B-68 to B-90 in Appendix B. Variation of
SPT N-value with depth of the twenty three bore holes are presented in Figure 4.15a
and 4.l6a. It is seen that water table exists at about 2.5 m from the existing ground
level (EGL). The variation of mean grain size (Dso) with depth for the twenty three
bore holes also have been presented in Figure 4.l5b and 4.16b. It is to be noted that
mean gram size of the samples could not be determined due to the shortage of
samples.
From Figure 4.l5a, it is seen that N-value varies from I to 35 up to 5 m depth from
EGL. The SPT-N-value varies from 3 to 20 for the depth from 5 to 10 m. Below this
level, SPT N-value varies from 3 to 40. From Figure 4.l5b, mean grain size varies
almost similar for the whole depth from 0.01 to 0.15 mm. For one sample the mean
grain size varies from 0.02 to 0.35 mm for the depth from 0 to 3.0 m. The soil type is
clay and clayey silt for the depth from EGL to 18 m. For the next 18 to 25 m depth
the soil is fine sand.
From Figure 4.16a, it is seen that N-value varies from I to 27 up to 10m depth from
EGL. Below this level SPT N-value varies from 3 to 48. From Figure 4.16b, mean
grain size varies from 0.003 to 0.006 mm up to depth 8 m from EGL. Mean grain
size varies from 0.003 to 0.007 mm for the depth from 8 to 20 m. For one sample
the mean grain size varies from 0.05 to 0.18 mm for the depth from 10 to 24 m. The
soil type is clay and clayey silt for the depth from EGL to 14 m. For the next 14 to 25
m depth the soil is silty fine sand and silty clay.
108
(b)
Mean grain size, 050
(mm)
0.1 0.2 0.3 0.400
5
Mirpur DOHSPlot- 325, 333 & 349
30
25
20
(a)
109
B •
Figure 4.14 Approximation locations of bore holes at Mirpur DOHS.
Uncorrected N-Yaluc
Mirpur DOHSPL-325, 333 & 349
30
Figure 4.15 (a) Depth versus SPI N-value and (b) Depth versus Dso at MirpurDOHS.
~ 10]: 10
oS.c .c15. 15.~ ~Cl Cl
15 15
0.20.150.10.05Mean grain size, D so (mm)
5
Uncorrected N-Value
20 20
~Fine sand
25 25
Ca)Mirpur DOHS
Cb) Mirpur DOHS30 30
~IO
~10
S-5 "'0- 15.u ~015 0
IS
Figure 4.16 (a) Depth versus SPT N-value and (b) Depth versus D50 at MirpurDOHS.
4.4.5 Sub-Soil Characteristics of Banani Old DOHS
The area Banani Old DOHS is situated in Dhaka. Data from five (5) boreholes werecollected from private agency for Banani Old DOHS site.
110
From Figure 4.17a, it is seen that N-value varies from 3 to 22 up to 5 m depth from
EGL. The SPT-N-value varies from 8 to 55 for the depth from 5 to 16 m. From
Figure 4.17b, mean grain size varies from 0.0 I to 0.09 mm for the depth from 0 to 10
m. Below the depth mean grain size varies from 0.06 to 0.20 mm. The soil type is
The field and laboratory test results of the five bore holes that are collected in this
study have been presented in Table 8-91 to B-95 in Appendix 8. Variation of SPT
N-value with depth of the five bore holes are presented in Figure 4.17a. It is seen that
water table exits at about 2.0 m from the existing ground level (EGL). The variation
of mean grain size (D50) with depth for the five boreholes also have been presented
in Figure 4.l7b. It is to be noted that mean grain size of the samples could not be
determined due to the shOliage of sampl.es.
Banani DOHS
IS
20 (b)Banani DOHS
Silty sandIS
20 (a)
Uncorrected N-value Mean grain size, D 50 (mm)0 10 20 30 40 0 0.1 0.2 0.30 0
GWT
S Clay SO~S
g g""0. Clayey Silt ..sv e-O
010 10
4.4.6 Sub-Soil Characteristics of Banasree
Figure 4.17 (a) Depth versus SPT N-value and (b) Depth versus Dso at Banani OldDOHS
III
clay and clayey silt for the depth is 13 m from EGL. For the next 13 to 16 m depththe soil is silty sand.
The area Banasree is situated in Dhaka. There are some blocks in the project area.
No borings are conducted at the site in the present study. Eleven bore data were
collected from private agencies Unique Boring and Engineering Limited and Icon
Engineering for Banasree site.
The field and laboratory test results of the eleven bore holes that are collected in this
study have been presented in Table B-96 to B-I06 in Appendix B. Variation of SPT
N-value with depth of the eleven bore holes are presented in Figure 4.18a. It is seen
that water table exits at about 1.5 m from the existing ground level (EGL). The
variation of mean grain size (Dso) with depth for the eleven boreholes also have been
presented in Figure 4.18b. It is to be noted that mean grain size of the samples could
not be determined due to the shortage of samples.
Banasree
Mean grain size, D so (mm)
0.1 0.2 0.3
(b)
5
20
30
25
WT
Banasree
Silty clay
Clay! Silty clay
5
00 10 20 30 40 50
Uncorrected N-Valuc
20
25
(a)30
g 10g 10
.c .c15. Silty sand 15.~ ~QQ15 15
112
Figure 4.18 (a) Depth versus SPT N-value and (b) Depth versus D50 at Banasree
From Figure 4.18a, it is seen that N-value varies from I to 10 up to 10m depth from
EGL. The SPT-N-value varies from 3 to 35 for the depth from 10 to IS m. Below
this level SPT N-value varies from IS to 50. From Figure 4.18b, mean grain size
varies from 0.02 to 0.10 mm for the depth from 0 to 27 m. The soil type is clay and
clayey silt for the depth from EGL to II m. For the next II to 16 m depth the soil is
silty sand. Below the level the soil is clay and silty sand.
4.4.7 Sub-Soil Characteristics of Keraniganj
The area Kholamura (Keraniganj) is situated in near Dhaka City. There is one block
in the project area. Two borings were conducted at the site in the present study.
Location of the boreholes are marked on the map of Keraniganj as shown in Figure
4.19.
The field and laboratory test results of the two bore holes that are conducted in this
study have been presented in Table B-1 07 to B-1 08 in Appendix B. Variation of 8PT
ZILA NA YANGONJ
aTHANA OJlIl
FIJlSnUftlGA CiAIllllDGE
•mANA SIFlAJO KHAN
aao
Union B und••
Unl"" thin K•••~n.111.", t$ldoK.,.,onlg .
ll<>r~h lDcalloo
~"
lEGEH
113
Figure 4.19 Approximate location of bore holes at Kholamura, Keraniganj nearDhaka City
N-value with depth of the two bore holes are presented in Figure 4.20a. It is seen that
water table exits at about 1.75 m from the existing ground level (EGL). The variation
of mean grain size (Dso) with depth for the two boreholes also have been presented in
Figure 4.20b. It is to be noted that mean grain size of the samples could not be
determined due to the shOliage of samples.
From Figure 4.20, it is seen that N-value varies from I to 10 up to 10m depth from
EGL. The SPT-N-value varies from 6 to 30 for the depth from 10 to 15 m. Below
this level SPT N-value varies from 12 to 43. Mean grain size varies from 0.02 to
0.38 mm for the depth from 0 to 5 m. From Figure 4.20b, mean grain size also varies
from 0.02 to 0.03 mm for the depth from 5 to 9 m. For the depth from 10 to 24.5 m
the mean size varies from 0.04 to 0.35 mm. The soil type is fine sand for the depth
from EGL to 4 m. For the next 5 to 9 m depth the soil is clayey silt. Below the level
the soil is silty sand and fine sand.
40
Mean grain size D (mm)50
o 0.1 0.2 0.3 0.4o
5
5030 40
Clayey silt
Fine sand
300
250 e- •~ 200 e-N
E •~ •3 150 l- •~ • •" •c:r100 l- • •50 l- •0 . . ,
10 15 20 25 30 35
10 20
Uncorrected N-value
Moisture content (%)
Figure 4.21 qu versus moisture content
114
oo
5
20 Fine sand 20
Kholamura Kholamura(Keraniganj)(a) (Keraniganj) (b)
25 25
Figure 4.20 (a) Depth versus SPT N-value and (b) Depth versus D50 at Kholamura,Keraniganj
~ 10~
10-5 Fine sand.c -515. &wQ Q
15 15Silty sand
Variation unconfined compressive strength with moisture content of the samples
tested in present study has been presented in Figure ti.21. Although an i~about qu
can be obtained for the figure, no definition correlation can be between qu and
moisture content can not be detennined.
4.5 SUMMARY
Field and laboratory density tests were conducted to determine the density of the soil
near the surface. Standard Penetration Test (SPT) and laboratory tests were also
conducted to determine the sub-soil characteristics of seven selected reclaimed areas.
The main observations of this chapter are given below:
• Field density tests were conducted near the surface (i.e., 0.15 tol.75 m depth
from ground level) at two reclaimed areas. Field density varied from 12.84 to
17.54 kN/m3• Grain size distributions of the soil samples collected from the same
depth of field density tests were also determined. It was observed that the soil
was silty sand in most cases. Relative density of the samples was also
determined. It was found that the relative density varied from 29 to 107%.
Although the relative density varied significantly, the relative density was more
than 50% in most cases. However, the relative density can not be compared with
the SPT N-value. Because there is no SPT data at the same depth at which
density tests were conducted.
• Sixteen borings were conducted and around one hundred bore hole data were
collected. From the borehole data, it was found that the water table exists at 1.5
to 2.5 m below ground level. The filling depth of the reclaimed areas varied from
3 to 8 m. The SPT N-value of the filling depth varied from I to 13. Mean grain
size and fines content of the soil in the filling depth varied from 0.002 to 0.34
mm and 2 to 15%, respectively. The characteristics of the soil beneath the filling
varied significantly.
o The sub-soil characteristics determined in this research is a valuable information
for the liquefaction potential analysis and foundation design. However, from
field and laboratory tests, it was observed that the soil characteristics varied
significantly. As a result, detailed sub-soil investigation is necessary for proper
foundation design.
115
Chapter Five
LIQUEFACTION POTENTIALOF RECLAIMED AREAS IN DHAKA CITY
5.1 GENERAL
Liquefaction is a soil behavior phenomenon in which a saturated soil looses a
substantial amount of strength due to high excess pore-water pressure generated by
and accumulated during strong earthquake ground shaking. Liquefaction potential of
a soil deposit can be estimated based on geomorphological information and existing
soil characteristics as described in Chapter 2. Geomorphological condition, existing
soil properties and SPT N-value indicate that the soil up to filling depth of the
reclaimed areas is susceptible to liquefaction. The detailed liquefaction potential
analysis is presented in this chapter.
5.2 LIQUEFACTION POTENTIAL OF RECLAIMED AREAS
Liquefaction potential index, FL has been determined based on the empirical
Equation 2.1 as described in Chapter 2. From the equation, it is clear that the cyclic
strength and the disturbing stress are required for the determination of FL. Cyclic
strength of the soil has been determined based on Japanese Code of Bridge Design
and Chinese Criterion as described in article 2.10.9 in Chapter 2. The disturbing
stress has been detennined based on Equation 2.17 that presented in Chapter 2. The
value of amax to determine the disturbing stress has been taken as 0.15g as Dhaka city
exists in the Zone 2 of Seismic Zonation map of Bangladesh (BNBC, 1993 and
Sharfuddin, 2001). Other researchers (Ansary and Rashid, 2000 and Rashid, 2000)
also used the similar values of ama, for Dhaka city. An example of liquefaction
potential analysis based on Japanese Code of Bridge Design and Chinese Criterion
has been presented in Figure 5.1. From the figure, it is seen that the FL determined
from Chinese Criterion and Japanese Code of Bridge Design varies significantly for
the same soil properties.
116
117
I J jF~ctor of safety, FFmes content, F (%) L
, (a ~O.15g)
o 2a 5a 1 0 ''--1 2" 1 d <, ,,--r-'~? , J--'--r--t-'r-
I j ~"~ J-. j 1 r! f 1 Jtj Non,liguifia~1 ! ~f f zone ~
j[i, ji\f ."~ \ Liquifiable
15 ~I LL )one1 --- __1 ---I ~// '1 .2J . ~'"'' t -0 '1:\"
.,\ ~ L --£:- JapaneseI l ~ ~ Chinese
""2Sl ....I.....-L..-.d
, D,,(mm)
30 "4 t 0.16
--N
10 20
SPTN-value
Sandy silt
5
Finesand
Mcdiu15 sand
1a
20
Deptb Soil(m) type
-a
Figure 5.1 Example of liquefaction potential analysis using SPT N-value(For am,x= O.15g).
-2
5.2.1 Liquefaction Potential of Bashundhara
Bore hole ,data was available for 58 locations at Bashundhara site. But liquefaction
potential analysis was conducted only for 18 locations because at other points the
soil was clayey soil. On the basis of soil characteristics of these locations that have
been presented in Figure 4.6a and 4.6b and Figure 4.8a and 4.8b of Chapter 4 and in
Tables B-1 to B-5 and B-26 to B-37 and B-50 in Appendix B. Both Japanese Code of
Bridge Design and Chinese Criterion, liquefaction potential of these 18 locations has
been presented in Table 5.1 and Figure 5.2 and Figure 5.3.
According to Japanese Code of Bridge Design, among these 18 locations, there is
only one liquefiable depth (i.e., 2.5 to 5.0 m) at one location.
According to Chinese Criterion, there are 10 locations where liquefaction may occur.
Among these, at seven locations the liquefaction depth varies from 3 to 13 m from
EGL. In other cases, the liquefiable depth is 2 to 16 m, 4 to 7 m and 6 to 9 m.
Therefore, it can be concluded that the probability of liquefaction at Bashundharaarea is low.
Table 5.1 Presence ofliquefiable soil strata at Bashundhara site
Block, Plot Soil type D" Range of liquefiable depth (m)&BHNo. (mm) Japanese Code Chinese CriterionI, 78, 0 I Silty sand 0.18-0.20 - EGL to 5.0
H, 827,02 Silty sand - - -K, 181,03 Silty sand 0.18-0.22 - EGL to 4.5G, Res, 04 Silty sand - - -A, 261, 05 Clay - - -1,66,01 Silty sand - - -I, 66, 02 Silty sand - - -1,66,03 Silty sand 0.10-0.10 - EGL to 3.01,66, 04 Silty sand - - -1,178,01 Silty sand - - -1,178,02 Silty sand - - -1,178,03 Silty sand 0.22-0.34 2.5 to 5.0 EGL to 10.01,178,04 Silty sand 0.15-0.34 - EGL to 12.0G, 936, 01 Silty sand 0.15-0.15 - EGL to 13.0G, 936, 02 Silty sand 0.12-0.15 - 4.0 to 7.0G, 936, 03 Silty sand 0.11-0.15 - EGL to 3.0G, 936, 04 Silty sand 0.15-0.152 - 2.0 to 16.0T-06,01 Silty sand 0.005-0.02 - 6.0 to 9.0
02,333,04 Silty sand 0.10-0.15 - EGL to 2.002,333;05 Silty sand 0.15-0.16 - EGL to 5.002,349,01 Silty sand 0.01-0.15 - EGL to 9.002,349,02 Silty sand 0.15-0.15 - EGL to 6.002, 349, 03 Silty sand 0.06-0.15 - EGL to 9.002,349,04 Silty sand 0.10-0.16 - EGL to 11.0
118
543
Japanese code
2
BashundharaBlock-I, G & T-6
oo
5
F = (Cyclic strength/Disturbing stress)L
5
1\ = (Cyclic strength! Disturbing stress)
1 2 3 4 5
25
30 (b)
E-10
~ vcv 0Q N
15 v:n'"<.=';;0';:;
20
Chinese criterion
5
119
F = (Cyclic strength! Disturbing stress)L
o 2 3 4 5o
5
F = (Cyclic strength! Disturbing stress)L
o 1 234 5o
Figure 5.2 Liquefaction potential vs depth (a) Chinese criterion and (b) Japanesecode at Bashundhara site,
Figure 5.3 Liquefaction potential vs depth (a) Chinese criterion and (b) Japanesecode at Bashundhara site,
g 10 ~ 10E-
-5 -5i} 0-
VQ v Qc
15 0 15 uNCv ::::n~ u<.= fj'5
0' <.=;:; '520 0'20
Non-liquifiable zone ;:;
(a) Bashundhara (b) Bashundhara25 25
~ 10..s..c15.vQ
15vc0NV
20 ~<.=';;0'
::l25
Bashundhara(a) Block-I, G & T-6
30
5.2.2 Liquefaction Potential of Pur bacha I New Model Town
Bore hole data was available for 3 locations at Purbachal New Model Town site.
Liquefaction potential analysis was conducted for 3 locations. On the basis soil
characteristics of these locations that have been presented in Figure 4.11 a and 4.11 b
of Chapter 4 and in Table B-59 to B-61 in Appendix B. Both Japanese Code of
Bridge Design and Chinese Criterion, liquefaction potential of these 3 locations has
been presented in Table 5.2 and Figure 5.4.
According to Japanese Code of Bridge Design, there is no liquefiable depth for 3
locations at Purbachal New Model Town.
According to Chinese Criterion, there are 2 locations where liquefaction may occur.
Liquefaction depth varies from 3.5 to 5 m from EGL at these two locations.
Therefore, it can be concluded that the probability of liquefaction at Purbachal NewModel Town area is low.
Table 5.2 Presence of liquefiable soil strata at Purbachal New Model Town site
BHNo. Soil type Dso Range ofliquefiable depth (m)(mm) Japanese Code Chinese Criterion
BH-I Silty sand - - -
BH-2. Silty sand 0.02-0.32 - EGL to 3.5BH-3 Silty sand 0.17-0.22 - EGL to 5.0
120
Japanese code
5
F = (Cyclic strength! Disturbing stress)L
o 1 2 3 4 5oChinese criterio
5
F = (Cyclic strength! Disturbing stress)L
o 1 2 3 4 5o
Figure 5.4 Liquefaction potential vs depth (a) Chinese criterion and (b) Japanesecode at Purbachal New Model Town.
121
~10 10
~-5 "'""- a" "Q " Q "" "15 2 15 2" ":g :g"" ""'5 '50"
0":.:i :.:i20Non-liquifiable zone 20
Non-liquifiable zone
Purbnachal New Purbnaehal New(a) Model Town (b) Model Town25 25
5.2.3 Liquefaction Potential of Uttara Model Town (Third Phase)
Bore hole data was available for 6 locations at Uttara Model Town (Third Phase)
site. Liquefaction potential analysis was conducted for 6 locations. On the basis soil
characteristics of these locations that have been presented in Figure 4.l3a and 4. I3b
of Chapter 4 and in Table B-62 to B-67 in Appendix B. Both Japanese Code of
Bridge Design and Chinese Criterion, liquefaction potential of these 6 locations has
been presented in Table 5.3 and Figure 5.5.
According to Japanese Code of Bridge Design, there is no liquefiable depth for 6
locations at Uttara Model Town (Third Phase).
Japanese code
5
FL
~ (Cyclic strength! Disturbing stress)
o I 2 3 4 5o
Non-liquifiable zone
10
15
20
Uttara Model Town(b) (Th ird Phase)25
Chinese criterion
Utlara Model Town(Third Phase)
Non-liquifiable zone
BHNo. Soil type D,o Range of liquefiable depth (m)
(mm) Japanese Code Chinese CriterionBH-I Silty sand - - -BH-2 Silty sand 0.19-0.21 - 6.0 to 10.0BH-3 Silty sand 0.17-0.23 - 3.0 to 7.0BH-4 Silty sand 0.17-0.20 EGL to 3.0BH-5 Silty sand. 0.10-0.18 - EGL to 5.0BH-6 Silty sand 0.10-0.26 - EGL to 7.0
(a)25
122
F ~ (Cyclic strength! Disturbing stress)L
o I 2 3 4 5o
Figure 5.5 Liquefaction potential vs depth (a) Chinese criterion and (b) Japanesecode at Uttara Model Town (Third Phase).
According to Chinese Criterion, there are 5 locations where liquefaction may occur.
The liquefiable depth varies from 3 to 7 m from EGL at 3 locations. For other two
locations, the liquefiable depth is 3 to 7 m and 6 to 10m.
Table 5.3 Presence of liquefiable soil strata at Uttara Model Town (Third Phase) site
Therefore, it can be concluded that the probability of liquefaction at Uttara Model
Town (Third Phase) area is low.
~E~..c0."CI ""15 0
N
":0'"<C'50-
:.:i20
5.2.4 Liquefaction Potential ofMirpor DOHS
Bore hole data was available for 23 locations at Mirpur DOHS site. But liquefaction
potential analysis was conducted only for 9 locations because at other locations the
soil was clayey soil. On the basis soil characteristics of these locations that have been
presented in Figure 4.16a and 4.l6b of Chapter 4 and in Table B-n to B-80 in
Appendix B. Both Japanese Code of Bridge Design and Chinese Criterion,
liquefaction potential of these 9 locations has been presented in Table 5.4 and Figure5.6.
According to Japanese Code of Bridge Design, there is no liquefiable depth for 9
locations among these 23 locations, at Mirpur DOHS site.
According to Chinese Criterion, there are 9 locations where liquefaction may occur.
The liquefiable depth varies from 2 to 11 m from EGL for all locations.
Therefore,. it can be concluded that the probability of liquefaction at Mirpur DOHSarea is low.
Table 5.4 Presence of liquefiable soil strata at Mirpur DOHS site
Block, Plot Soil type D50 Range of liquefiable depth (m)&BHNo. (mm) Japanese Code Chinese Criterion02,333,01 Silty sand 0.15-0.15 - EGL to 5.002,333,02 Silty sand 0.12-0.16 - EGL to 3.002, 333, 03 Silty sand 0.15-0.15 - EGL to 2.002, 333, 04 Silty sand 0.10-0.15 - EGL to 2.002,333,05 Silty sand O.I5-0. I6 - EGL to 5.002,349,01 Silty sand 0.01-0.15 - EGL to 9.002,349,02 Silty sand 0.15-0.15 - EGL to 6.002,349,03 Silty sand 0.06-0. I5 - EGL to 9.002,349,04 Silty sand 0.10-0.16 - EGL to 11.0
123
Mirpur DOHS
5
F = (Cyclic strength!Disturbing stress)L
o I 2 3 4 5oJapanese code
30 (b)Mirpur DOHS(a)
5
F = (Cyclic strength/ Disturbing stress)L
00 1 2 3 4 5
Chinese criterion
30
Figure 5.6 Liquefaction potential vs depth (a) Chinese criterion and (b) Japanesecode at Mirpur DOHS.
124
~ 10 ~ 10E E~..c ~
..c0. 0.<UQ <U
Q15 15<U
<Uc: c:0f:lN
<U<U20 :0
20 :0'" '"t;:: t;::.:; '5.a- a-;J ;J25 Non-liquifiable zone 25
5.2.5 Liquefaction Potential of Kholamura, Keraniganj
Borehole data was available for 2 locations at Kholamura (Keraniganj) site.
Liquefaction potential analysis was conducted for 2 locations. On the basis soil
characteristics of these locations that have been presented in Figure 4.20a and 4.20b
of Chapter 4 and in Table B-107 to B-108 in Appendix B. Both Japanese Code of
Bridge Design and Chinese Criterion, liquefaction potential of these 2 locations has
been presented in Table 5.5 and Figure 5.7.
According to Japanese Code of Bridge Design, there is liquefiable depth from EGL
to 5 m at one location ofKholamura, Keraniganj site.
Kholamura(Keraniganj)
Non-liquifiablezone
~ Japanese code
20
(b)30
25
F = (Cyclicstrength!Disturbingstress)L
o 1 2 3 4 5o
5
""0N~ 10 "E :0~ '"-a ""'5" 0-Q :.:i
15
Kholamura(Keraniganj)
Chinese criterion
Non-liquifiablezone
(a)
5
FL~ (C)<Olicstrength!Disturbingstress)
o I 2 3 4 5o
15
125
20
25
30
Figure 5.7 Liquefaction potential vs depth (a) Chinese criterion and (b) Japanesecode at Kholamura, Keraniganj site.
According to Chinese Criterion, there are 2 locations where liquefaction may occur.
Liquefaction depth varies from EGL to 10m and from 3 to 12 m at two locations.
BHNo. Soil type Dso Range ofliquefiable depth (m)
(mm) Japanese Chinese Criterion
Code
BH-I Silty sand 0.02-0.15 - 3.0 to 12.0
BH-2 Silty sand 0.18-0.39 EGLto 5.0 EGL to 10.0
Therefore, it can be concluded that the probability of liquefaction at Kholamura
(Keraniganj) area is low.
Table 5.5 Presence of liquefiable soil strata at Kholamura, Kearniganj
5.2.6 Liquefaction Potential of Banani Old DOHS
Borehole data was available for 5 locations at Banani Old DOHS site. But
liquefaction potential analysis was not conducted for 5 locations because all points
the soil was clayey soil. On the basis soil characteristics of these locations that have
been presented in Table B-91 to B-95 in Appendix B. So, there is no probability of
liquefaction at Banani Old DOHS site based on this data.
5.2.7 Liquefaction Potential of Banasree
Bore hole data was available for 11 locations at Banasrce site. But liquefaction
potential analysis was not conductcd for II locations because all points the soil was
clayey soil. On the basis soil characteristics of these locations that have been
presented in Table B-96 to B-I06 in Appendix B. So, there is no probability of
liquefaction at Banasree site based on this data.
5.3 CRITICAL N-VALUE
Critical N-value (i.e., Corrected N-value corresponding to FL = 1.0) has been plotted
for different fines content in Figure 5.8. Here it is to be noted that some data points
have been avoided while plotting this graph because of high scatter points. From
Figure l5'i1 it is seen that critical N-value for the present study is almost similar that~..••.. ",
wa~presented by Yasuda (1988)
126
127
35
.: -- ~,.
Present study~
20 25 3015
..Not Liq.ll(:fii\p Ie...
Yasuda (1988)
Fines content (%)
• Liqudiable
5 10
Figure 5.8 Critical N-value vs fines content
25
20<U;:l(;j
15;:-,Z(;j
10(j.-~'CU
5
00
5.4 SUMMARY
The main focus of this research work is to determine the liquefaction potential of
selected reclaimed areas in and around Dhaka city. Firstly, liquefaction potential has
been estimated based on geographical unit, soil characteristics (Rao, 2003) and SPT
N-value. Secondly, the liquefaction potential has been determined based on
empirical equations - Japanese Code of Bridge Design (Tatsuoka et. ai, 1980) and
Chinese Criterion (Ishihara, 1990).
o About one hundred ten bore hole data was col1ected from seven reclaimed sites
of Dhaka city. Liquefaction analysis was conducted at 38 locations according to
both Japanese Code of Bridge Design and Chinese Criterion. Liquefaction
potential analysis was not conducted at other 72 locations because the soil was
clayey type at tshose locations.
• According to Japanese Code of Bridge Design, there are only two points where
liquefiable depth exists. Liquefiable depths of those points are 2.5 to 5.0 m and
5.0 m from Existing Ground Level (EGL). In general, it can be summarized that
the liquefaction probability is very low in such areas. On the other hand,
according to Chinese Criterion, there are 28 locations where liquefiable depth
exists. The liquefiable depth varied from 2.0 to 13.0 m from EGL.
• It is observed that the liquefaction potential varied significantly according to
Japanese Code of Bridge Design and Chinese Criterion. Because the Japanese
Code of Bridge Design considers SPT N-value corrected for overburden pressure
and fines content and mean grain size. But the Chinese Criterion considers only
corrected SPT N-value. In author's observation, it appears that the Chinese
Criterion can be used for clean sand. But the soil in question has fines also. So,
the liquefaction potential determined based on Chinese Criterion may be
overestimated.
• It can be concluded that there is a low probability of liquefaction to occur in such
areas of Dhaka city because the soil used for filling has fines. However, the
presence of fines in a hydraulic fill means greater compressibility and greater
difficulty in compaction of the fill. Fines also reduce permeability and hence the
rate of drainage.
128
Chapter Six
CONCLUSIONS AND RECOMMENDATIONS
6.1 GENERAL
The purpose of this research was to determine the sub-soil characteristics and liquefaction
potential of reclaimed areas of Dhaka city. The research includes survey of development
procedure of reclaimed areas and laboratory and field tests to determine the sub-soil
characteristics of such areas. The study was extended up to determination of liquefaction
potential of the selected areas. This chapter is devoted to present the summary and salient
conclusions derived from this study.
6.2 DEVELOPMENT OF RECLAIMED AREAS
Reclaimed areas are being developed in and around Dhaka city. Main reclaimed areas
have been marked on the Dhaka city map. Soils from river bed and river banks of
rivers such as Turag, Buriganga, Dhaleshwari, Sitalakhya and Meghna are used for the
development of such areas. Fineness modulus, mean grain size and fines content of the
source materials varies from 0.003 to 0.94, 0.012 to 0.25 mm and 2.0 to 95%,
respectively. There are four methods in practice to develop these areas. Generally, soil
is collected from riverbeds by cutter-suction dredging into a barge, which is carried to
the nearest river site. Soil is then pumped through pipes in a slurry form after mixing
with water, and transferred to the point of deposition. A proposal has been presented
for the proper reclamation of reclaimed sites. The sites should be developed in such a
way that the relative density should be greater or equal to 70%. If 70% relative density
is not achieved, the site should be improved applying ground improvement techniques.
However, more investigations are necessary to develop a proper reclamation procedure.
129
6.3 SUB-SOIL CHARACTERISTICS OF RECLAIMED AREAS
Field density tests were conducted near the surface (i.e., 0.15 to 1.75 m depth from ground
level) at two reclaimed areas. Field density varied from 12.84 to 17.54 kN/mJ. Grain size
distributions of the soil samples collected from the same depth of field density tests were
also determined. It was observed that the soil was silty sand in most cases. Relative
density of the samples was also determined. It was found that the relative density varied
from 29 to 107%. Although the relative density varied significantly, the relative density
was more than 50% in most cases. However, the relative density can not be compared
with the SPT N-value. Because there is no SPT data at the same depth at which density
tests were conducted.
Sixteen borings were conducted and around one hundred bore hole data were collected.
From the bore hole data, it was found that the water table exists at 1.5 to 2.5 m below the
existing ground level. The filling depth of the reclaimed areas varied from 3 to 8 m. The
SPT N-value of the filling depth varied from 1 to 13. Mean grain size and fines content of
the soil in the filling depth varied from 0.002 to 0.34 mm and 2 to 15%, respectively. The
characteristics of the soil beneath the filling varied significantly.
The sub-soil characteristics determined in this research is valuable information for the
liquefaction potential analysis and foundation design. However, from field and laboratory
tests, it was observed that the soil characteristics varied significantly. As a result, detailed
sub-soil investigation is necessary for proper foundation design.
6.4 LIQUEFACTION I)OTENTIAL OF RECLAIMED AREAS
About one hundred ten bore hole data was collected from seven reclaimed sites of Dhaka
city. Liquefaction analysis was conducted at 38 locations according to both Japanese
Code of Bridge Design and Chinese Criterion. Liquefaction potential analysis was not
conducted at other 72 locations because the soil was clayey type at those locations.
130
According to Japanese Code of Bridge Design, there are only two points where
liquefiable depth exists. Liquefiable depths of those points are 2.5 to 5.0 m and 5.0 m
from Existing Ground Level (EGL). In general, it can be summarized that the
liquefaction probability is very low in such areas. On the other hand, according to
Chinese Criterion, there are 28 locations where liquefiable depth exists. The liquefiable
depth varied from 2.0 to 13.0 m from EGL.
It is observed that the liquefaction potential varied significantly according to Japanese
Code of Bridge Design and Chinese Criterion. Because the Japanese Code of Bridge
Design considers SPT N-value corrected for overburden pressure and fines content and
mean grain size. But the Chinese Criterion considers only corrected SPT N-value. In
author's observation, it appears that the Chinese Criterion can be used for clean sand. But
the soil in question has fines also. So, the liquefaction potential determined based on
Chinese Criterion may be overestimated.
It can be concluded that there is a low probability of liquefaction to occur in such areas of
Dhaka city because the soil used for filling has fines. However, the presence of fines in a
hydraulic fill means greater compressibility and greater difficulty in compaction of the
fill. Fines also reduce permeability and hence the rate of drainage.
6.5 SCOPES FOR FUTURE RESEARCHS
The research conducted in the survey, testing program and empirical analysis has led to
many questions and subsequent future research interests. The areas of future research are
listed below followed by brief comments:
a) Study can be conducted to prepare guidelines for reclamation procedure to avoid
liquefaction of reclaimed areas. For developing a rational method for reclamation
of such areas to avoid liquefaction- pilot project and more detailed laboratory tests
can be conducted.
131
b) Relative density tests were conducted near the surface of reclaimed sites. Study
can be conducted to determine the correlation between relative density and SPT
N-value by conducting density tests and SPT at the same level.
c) Liquefaction potential can be determined using other methods/models to compare
with the results obtained in this study.
d) Liquefaction potential map of the areas can be determined usmg the results
obtained in this study.
e) Study can be conducted to determine the suitable ground improvement techniques
for such areas.
f) It was observed that the liquefaction potential determined in Japanese Code and
Chinese Criterion varied significantly. More detailed study can be conducted to
determine the liquefaction potential precisely. Laboratory tests such as cyclic
loading test, shaking table test can be conducted to determine the real cyclic
strengths of the soils.
132
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140
APPENDIX-A
EUROPEAN MACRO SEISMIC SCALE
I. Not felt
a) Not felt, even under the most favorable circumstances.
b) No effect.
c) No damage.
II. Scarcely felt
a) The tremor is felt only by a very few (less than 1%) individuals at rest
and in an especially receptive position indoors.
b) No effect..
c) No damage.
III. Weak
a) The earthquake is felt indoors by a few. People at rest feel a swaying
or light trembling.
b) Hanging objects swing slightly.
c) No damage.
IV. Largely observed
a) The earthquake is felt indoors by many and felt outdoors only by very
few. A few people are awakened. The level of vibration is not
frightening. The vibration is moderate. Observers feel a slight
trembling or swaying of the building, room or bed, chair etc.
b) China, glasses, windows and doors rattle. Hanging objects swing.
Light furniture shakes visibly in a few cases. Woodwork cracks in a
few cases.
c) No damage.
V. Strong
a) The earthquake is felt indoors by most, outdoors by few. A few people
are frightened and run outdoors. Many sleeping people awake.
141
•••
Observers feel a strong shaking or rocking of the whole building, room
or furniture.
b) Hanging objects swing considerably. China and glasses clatter
together. Small, top-heavy and/or precariously supported objects may
be shifted or fall down. Doors and windows swing open or shut. In a
few cases window panes break. Liquids oscillate and may spill from
well-filled containers. Animals indoors may become uneasy.
c) Damage of grade I to a few buildings.
VI. Slightly damaging
a) Felt by most indoors and by many outdoors. A few persons lose their
balance. Many people are frightened and run outdoors.
b) Small objects of ordinary stability may fall and furniture may be
shifted. In few instances dishes and glassware may break. Farm
animals (even outdoors) may be frightened.
c) Damage of grade I is sustained by many buildings; a few suffer
damage of grade 2.
VII. Damaging
a) Most people are frightened and try to run outdoors. Many find it.
difficult to stand, especially on upper floors.
b) Furniture is shifted and top-heavy furniture may be overturned.
Objects fall from shelves in large numbers. Water splashes from
containers, tanks and pools.
c) Many buildings of vulnerability class B and a few of class C suffer
damage of grade 2. Many buildings of class A and a few of class B
suffer damage of grade 3; noticeable in the upper parts of buildings.
VIII. Heavily damaging
a) Many people find it difficult to stand, even outdoors.
b) Furniture may be overturned. Objects like TV sets, typewriters etc. fall
to the ground. Tombstones may occasionally be displaced, twisted or
overturned. Waves may be seen on very soft ground.
142
c) Many buildings of vulnerability class C suffer damage of grade 2.
Many buildings of class B and a few of class C suffer damage of grade
3. Many buildings of class A and a few of class B suffer damage of
grade 4; a few buildings of class A suffer damage of grade 5. A few
buildings of class 0 suffer damage of grade 2.
IX. Destructive
a) General panic. People may be forcibly thrown to the ground.
b) Many monuments and columns fall or are twisted. Waves are seen on
soft ground.
c) Many buildings of vulnerability class C suffer damage of grade 3.
Many buildings of class B and a few of class C suffer damage of grade
4. Many buildings of class A and a few class B suffer damage grade 5.
Many buildings of class 0 suffer damage of grade 2; a few suffer
grade 3. A few buildings of class E suffer damage of grade 2.
X. Very destructive
a) Many buildings of vulnerability class C suffer damage of grade 4.
Many buildings of class B and a few class C suffer damage of grade 5,
as do most buildings of class A. Many buildings of class 0 suffer
damage of grade 3; a few suffer grade 4. Many buildings of class E
suffer damage of grade 2; a few suffer grade 3. A few buildings of
class F suffer damage of grade 2.
XI. Devastating
a) Most buildings of vulnerability class C suffer damage of grade 4. Most
buildings of class B and many of class C suffer damage of grade 5.
Many building buildings of class 0 suffer damage of grade 4; a few
suffer grade 5. Many buildings of class E suffer damage of grade 3; a
few suffer grade 4. Many buildings of class F suffer damage of grade
2, a few suffer grade 3.
XII. Completely devastating
a) Practically all structures above and below ground are destroyed.
143
OLDHAM SCALE OF INTENSITY
I. The first isoseist includes all places where the destruction of brick and stone
buildings was practically universal.
II. The second, those places where damages to masonry or brick buildings was
universal, often serious, amounting in some cases to destruction.
III. The third, those places where the earthquake was violent enough to damage
all or nearly all brick buildings.
IV. The forth, those places where the earthquake was universally felt, severe
enough to disturb furniture and loose objects, but not severe enough to cause
damage, except in a few instances, to brick buildings.
V. The fifth, those places where the earthquake was smart enough to be generally
noticed, but not severe enough to cause any damage.
VI. The sixth; all those places where the earthquake was only noticed by a small
proportion of people who happened to be sensitive, and being seated or lying
down were favorably situated for observing it.
144
THE ROSSI-FOREL SCALE OF INTENSITY
The most commonly used form of the Rossi-Forel (R. F.) Scale reads as follows:
I. Microseismic Shock. Recorded by a singly seismograph or by seismographs
of the same model, but not by several seismographs of different kinds: the
shock felt by an experienced observer.
II. Extremely feeble shock. Recorded by several seismographs of different kinds;
felt by a small number of persons at rest.
III. Very feeble shock. Felt by several persons at rest; strong enough for the
direction duration to be appreciable.
IV. Feeble shock. Felt by persons in motion; disturbance of movable objects,
doors, windows, cracking of ceilings.
V. Shock of moderate intensity. Felt generally by everyone; disturbance of
furniture, beds, etc., ringing of some bells.
VI. Fairly strong shock. General awakening of those asleep; general ringing of
bells; oscillation of chandeliers; stopping of clocks; visible agitation of trees
and shrubs; some startled persons leaving their dwellings.
VII. Strong shock. Overthrow of movable objects; fall of plaster; ringing of church
bells; general panic; without damage to buildings.
VIII. Very string shock. Fall of chimney; cracks in the walls of buildings.
IX. Extremely strong shock. Partial or total destruction of some buildings.
X. Shock of extreme intensity. Great disaster; ruins; disturbance of the strata,
fissures in the ground, rock falls from mountains.
145
MODIFIED MERCALLI INTENSITY (MMI) SCALE, 1956VERSION
In the 1956 version, some items are omitted for definite reasons, and few additional
notes are included, with initials (CFR) to separate them from the original scale by C.
F. Richter.
To avoid arr,biguity of language, the quality of masonry, brick or otherwise, is
specified by the following lettering.
Masonry A: Good workmanship, mortar and design; reinforced, especially laterally
and bound together by using steel, concrete, etc.; designed to resist lateral
forces.
Masonry B: Good workmanship and mortar; reinforced but not designed in detail to
resist lateral forces.
Masonry C: Ordinary workmanship and mortar; no extreme weakness like failing to
tie in at corners, but neither reinforced nor designed against horizontal
forces.
Masonry D: Weak materials, such as adobe, poor mortar, low standards of
workmanship, weak horizontally.
Modified Mercalli Intensity (MMI) Scale, 1956 Version
MMI Description
I Not felt. Marginal and long period effects of large earthquakes.
II Felt by persons at rest, on upper floors, or favorably placed.
III Felt indoors. Hanging objects swing. Vibration like passing of light trucks.
Duration estimated. May not be recognized as an earthquake.
IV Hanging objects swing. Vibration like passing of heavy trucks; or sensation
of a jolt like a heavy ball striking the walls. Standing motor cars rock.
146
Windows, dishes, doors rattle. Glasses clink. Crockery clashes. In the
'upper range of IV, wooden walls and frame creak.
V Felt outdoors; direction estimated. Sleepers wakened. Liquids disturbed,
some spilled. Small unstable objects displaced or upset. Doors swing,
close, open. Shutters, pictures move. Pendulum clocks stop, start, change
rate.
VI Felt by all. Many frightened and run outdoors. Persons walk unsteadily.
Windows, dishes, glassware broken. Knickknacks, books, etc., off shelves.
Pictures off walls. Furniture moved or overturned. Weak plaster and
masonry D cracked. Small bells ring (church, school). Trees, bushes
shaken (visibly, or heard to rustle).
VII Difficult to stand. Noticed by drivers of motor cars. Hanging objects
quiver. Furniture broken. Damage to masonry D, including cracks. Weak
chimneys broken at roof line. Fall of plaster, loose bricks, stones, tiles,
cornices (also unbraced parapets and architectural ornaments). Some cracks
in masonry C. Waves on ponds; water turbid with mud. Small slides and
caving in along sand or gravel banks. Large bells ring. Concrete irrigation
ditches damaged.
VIII Steering of motor cars affected. Damage to masonry C; partial collapse.
Some damage to masonry B; none to masonry A. Fall of stucco and some
masonry walls. Twisting, fall of chimneys, factory stacks, monuments,
towers, elevated tanks. Frame houses moved on foundations if not bolted
down; loose panel walls thrown out. Decayed piling broken off. Branches
broken from trees. Changes in flow or temperature of springs and wells.
Cracks in wet ground and on steep slopes.
IX General panic. Masonry D destroyed; masonry C heavily damaged,
sometimes with complete collapse; masonry B seriously damaged.
(General damage to foundations.) Frame structures, if not bolted, shifted
off foundations. Frames racked. Serious damage to reservoIrs.
147
XI Rails bent greatly. Underground pipelines completely out of service.
XI Damage nearly total. Large rock masses displaced. Lines of sight and level
. distorted. Objects thrown into the air.
-' .148
Effects
Only recorder by Seismographs
Only felt by individual people at rest.
Only felt by few people.
Felt by many people. Dishes and doors rattle.
Hanging objects swing, many sleeping people awaken
Slight damage in buildings and small cracks in plaster.
Cracks in plaster, gaps in walls and chimneys.
W ide gaps in masonry, parts of gables and cornices fall down.
In some buildings walls and roofs collapse, landslips.
Collapse of many buildings, cracks in ground up to widths of I m.
Many cracks in ground, landslips and falls of rocks.
Strong changes in the surface ofthe ground.
II
III
IV
V
VI
VII
VIII
IX
X
XI
XII
Underground pipes broken. Conspicuous cracks in ground. In alluvial areas
sand and mud ejected, earthquake fountains, sand craters.
X Most masonry and frame structures destroyed with their foundations. Some
well-built wooden structures and bridges destroyed. Serious damage to
dams, dikes, embankments. Large landslides. Water thrown on banks of
canals, rivers, lakes, etc. Sand and mud shifted horizontally on beaches and
flat land. Rails bent slightly.
Intensity (Grade)
I a v Xo(grade) (cm/sec2) (cm/sec) (mm)
V 12-25 1.0-2.0 0.5-1.0VI 25-50 2.1-4.0 1.1-2.0VII 50-100 4.1-8.0 2.1-4.0VlIl 100-200 8.1-16.0 4.1-8.0IX 200-400 16.1-32.0 8.1-16.0X 400-800 32.1-64.0 16.1-32.0
Where,
I = Intensity of earthquakes
a =Ground acceleration in cm/sec2 for periods between 0.1 sec and 0.5 sec.
v = Velocity of g round oscillation in cm/sec. for periods between 0.5 sec and
2.0 sec
Xo = Amplitude of movement of centre of gravity of the pendulum mass in
mm. The natural period of the pendulum is 0.25 sec, the logarithmic
decrement is 0.5.
149
Table B-1 Test results of borehole BH-OI, Block-I, Plot-78 (Bashundhara)
Depth SPT-N Soil description Os w, F, D50 PI(m) (%) (%) (mm)1.52 4 Silty fine sand 2.7 23.44 8 0.183.05 5 2.68 25.95 3 0.204.57 3 39 0.116.10 2 Silty clay 197.62 2 289.15 110.67 3 2312.20 4 3113.72 1415.24 26 3016.77 1218.29 16 2319.82 13 29
Table B-2 Test results of borehole BH-02, Block-H, Plot-827 (Bashundhara)
Depth SPT-N Soil description Os w, F, D,o PI(m) (%) ( %) (mm)1.52 7 Silty fine sand 2.65 17 9 0.2803.05 7 17 9 0.2704.57 10 2.66 20 17 0.1406.1 10 2.65 20 20 0.1407.62 6 2.66 21 20 0.1309.15 7 2.65 20 13 0.15010.67 7 2.66 21 13 0.14512.2 8 25 34 0.09513.72 9 27 33 0.10015.24 14 Clay 1516.77 16 1518.29 18 2219.82 20 21
Table B-3 Test results of borehole BH-03, Block-K, Plot-181 (Bashundhara)
Depth SPT-N Soil description Os w, F, D50 PI(m) (%) ( %) (mm)1.52 6 Silty sand 2.69 18 5 0.193.05 8 2.69 5 7 0.184.57 7 2.69 7 7 0.226.1 14 Clay 337.62 13 . 379.15 II 2010.67 9 2512.2 7 2113.72 12 1215.24 20 2316.77 29 Silty sand 18 5718.29 38 2.69 16 38 0.1619.82 43 7 22 0.19
150
APPENDIX-B
Table 8.4 Test results of bore bole BH-04, Block-G, Plot-Res. ICorn. (Bashundbara)
Depth SPT-N Soil description Gs F, Dso. PI(rn) ( 'Yo) (rnrn)1.52 4 Silty sand 2.64 20 0.123.05 3 2.67 13 0.184.57 4 Clay 346.1 37.62 6 339.15 9 2410.67 12 1812.2 1413.72 15 1915.24 16 2116.77 18 2018.29 1919.82 21 22
Table 8.5 Test results of borehole BH-05, Block-A, Plot-26I (Bashundhara)
Depth SPT-N Soil description Gs w, F, Dso PI(rn) ('Yo) ( 'Yo) (rnrn)1.52 I Clay 293.05 2 264.57 16.1 3 387.62 13 339.15 14 3210.67 1412.2 IS 1513.72 17 2115.24 20 016.77 21 2518.29 23 2019.82 24 19
Table 8-6 Test results of borehole BH-01, Block-A, Plot-435 (Bashundhara)
Depth SPT-N Soil description F, Dso PI(rn) ('Yo) (rnrn)1.52 5 Fine sand2.29 I
Light brown 87 0.0093.20 24.12 4
clay
5.03 3 Organic clay5.95 27.62 2
Grey clay with9.15 910.67 IS fine sand
12.20 813.72 1015.24 1916.77 50 91 0.02218.29 72 Light brown
18clay with fine
19.82 sand21.34 19
27 -22.87
151
Table B-7 Test results of borehole BH-02, Block-A, Plot-435 (Bashundhara)
Depth SPT-N Soil description F, D50 PI(m) (%) (mm)
Light brown1.52 5 clay with fine
sand2.29 3
Light brown3.20 2 91 0.0134.12 4 clay with fine
sand5.03 35.95 3 Dark gray7.62 3 organic clay9.15 1510.67 1I Gray to light12.20 10 brown clay13.72 10 with fine sand15.24 1616.77 57 Light brown 56 0.05218.29 65 silt & fine sand19.82 16
21.34 19 Very clay withfine sand
22.87 22
Table B-8 Test results of borehole BH-03, Block-A, Plot-435 (Bashundhara)
Depth SPT-N Soil description F, D50 PI(m) ( %) (mm)1.52 3 Light brown2.29 2 clay with fine
sand3.20 2 Silt with sand4.12 3 Light brown5.03 4 clay with fine 95 0.0095.95 3 sand7.62 3 clay with sand9.15 13 Gray clay with10.67 10 fine sand12.20 1013.72 915.24 16 Light brown 87 0.03016.77 57 silt some fine18.29 67 sand19.82 17 Gray clay with21.34 19 fine sand
22.87 20
152
Table B-9 Test results of borehole BH-OI, Block-B, Plot-242 (Bashundhara)
Depth SPT-N Soil description Gs wo Yd'Y F, D,o PI go Ef eo C,(m) (%) (kN/m') ( %) (mm) (kPa) (%)
1.52 2 Soft silty clay -2.74 6 - 33 13.02 98 0.006 26 29.5 20.03.66 2 SilNclay 2.67 31 13.26 44.3 16.0 0.99 0.257.01 13 Silty clay with - 99 0.004
organic trace9.76 13 Silty clav -13.72 31 SillY sand - 89 0.02715.24 33 Silty clay -16.77 36 -18.29 38 -
Table B-IO Test results of borehole BH-02, Block-B, Plot-242 (Bashundhara)
Depth SPT-N Soil description Gs wo Yd'Y F, D,o PI go Ef eo C,(m) (%) (kN/m') ( %) (mm) (kPa) (%)
1.52 4 Silty clay2.44 8 29 13.63 71.7 16.03.35 2 33 13.07 96 0.006 27 30.6 20.07.32 13 .
8.54 159.76 13 95 0.00712.80 2813.72 3015.24 3116.77 34 94 0.00618.29 37
Table B-ll Test results of borehole BH-03, Block-B, Plot-242 (Bashundhara)
Dept SPT-N Soil description Gs wo Yd'Y F, D,o PI go Ef eo C,h (%) (kN/m') ( %) (mm) (kPa) (%)(m)1.52 2 Silty clay.2.74 8 2.68 33 13.0 97 0.005 29.5 20 1.03 0.263.35 2 32 13.2 33.7 187.01 129.76 19 95 0.00612.80 30 Medium silt-13.72 29 sand with trace 82 0.02715.24 28 clay15.85 30 Silty clay16.77 3318.29 35
153
Table B-12 Test results of borehole BH-04, Block-B, Plot-242 (Bashundhara)
Depth SPT-N Soil description Gs w, 1,'1' F, D50 PI g, Er eo C,(m) (%) (kN/m') (%) (mm) (kPa) (%)1.52 2 Silty clay2.74 9 32 13.1 31.6 203.35 2 33 12.9 96 0.007 27 27.4 205.49 47.32 68.84 1I9.76 18 Medium silt- 85 0.01711.59 20 sand deposit13.72 21 with trace clay.15.24 2215.85 3016.77 33 Silty clay 93 0.00718.29 36
Table B-13 Test results of borehole BH-05, Block-B, Plot-242 (Bashundhara)
Depth SPT-N Soil description Gs w, 1''1' F, D50 PI g, Er eo C,(m) (%) (kN/m') (%) (mm) (kPa) (%)1.52 22.74 6 32 13.2 98 0.005 273.96 2 Silty clay 2.68 29 13.6 35.9 18 0.94 0.237.32 10 65.4 168.54 219.76 2113.72 27 Silty sand with15.24 28 81 0.02216.16 20
trace clay
16.77 1918.29 2819.82 40 -21.34 44 Silty clay22.87 4524.39 45 92 0.00525.91 48
Table B-14 Test results of borehole BH-OI, Block-F, Plot-600 & 601 (Bashundhara)
Depth SPT-N Soil description F, D50 PI(m) (%) (mm)1.52 3 Silty clay3.66 16.10 5 97 0.010 277.32 119.76 1410.67 1512.20 1512.80 1813.72 18 95 0.014 27
2615.24 26 Clayey silt with16.77 24 trace fine sand18.29 22
154
Table B-15 Test results of borehole BH-02, Block-F, Plot-600 & 601 (Bashundhara)
Depth SPT-N Soil description F, D,o PI(m) ( %) (mm)1.52 4 Silty clay3.96 I 98 0.0087.62 5 Organic silty8.54 15 clay9.76 14 Silty clay10.67 1412.20 14 99 0.008 2713.11 1713.72 18 Clayey silt with15.24 20 trace fine sand16.77 2218.29 22
Table B-16 Test results of borehole BH-03, Block-F, Plot-600 & 601 (Bashundhara)
Depth SPT-N Soil description F, D,o PI(m) ( %) (mm)1.52 2 Silty clay3.66 I7.62 5 Organic silty 98 0.009
clav8.84 13 Silty clay9.76 1410.67 1512.20 1513.11 1713.72 1815.24 19 Clayey silt with16.77 19 trace fine sand 93 0.016 2018.29 20
Table B-17 Test results of borehole BH-04, Block-F, Plot'600 & 601 (Bashundhara)
Depth SPT-N Soil description F, D,o PI(m) (%) (mm)1.52 2 Silty clay3.66 I 99 0.0097.32 98.54 1310.67 1211.59 1012.20 1113.72 1214.33 2015.24 19 Clayey silt with 93 0.012 2016.77 17 trace fine sand18.29 16
155
Table B-18 Test results of borehole BH-05, Block-F, Plot-600 & 601 (Bashundhara)
Depth SPT-N Soil description F, D,o PI(m) ( %) (mm)
1.52 3 Silty clay3.66 36.71 118.54 14 97 0.010 2713.41 1613.72 1614.63 2215.24 2216.77 2118.29 2119.82 2321.34 24 Clayey silt with
22.87 24 trace fine sand 91 0.01624.39 2425.91 2627.44 27
Table B-19 Test results of borehole BH-06, Block-F, Plot-600 & 601 (Bashundhara)
Depth SPT-N Soil description F, D,o PI(m) (%) (mm)1.52 2 Silty clay3.66 36.71 4 97 0.0098.23 1010.67 1212.20 1712.80 2213.72 2315.24 "22 93 0.009 2116.77 20 Clayey silt with18.29 18 trace sand
Table B-20 Test results of borehole BH-07, Block-F, Plot-600 & 601 (Bashundhara)
Depth SPT-N Soil description F, D,o PI(m) ( %) (mm)1.52 2 Silty clay3.66 26.71 38.23 11 98 0.011 2710.67 1212.20 1512.80 1513.72 2015.24 2316.77 24 Clayey silt with 95 0.01018.29 21 trace fine sands
- 19.50 19
156
Table B-21 Test results of borehole BH-08, Block-F, Plot-600 & 601 (Bashundhara)
Depth Soil description F, D" PI(m) SPT-N ( %) (mm)1.52 23.66 II6.71 58.23 8 99 0.009 2810.67 10 Silty clay12.20 1812.80 1813.72 2615.24 2516.77 2318.29 2319.82 2421.34 24 Clayey silt with22.87 21 trace fine sand24.39 2125.91 24 91 0.01527.44 26
Table B-22 Test results of borehole BH-09, Block-F, Plot-600 & 601 (Bashundhara)
Depth SPT-N Soil description F, D" PI(m) . ( %) (mm)1.52 2 Silty clay3.66 I6.71 2 97 0.0098.23 810.67 812.20 1212.80 1213.72 -1715.24 1716.77 24 Clayey silt with18.29 23 trace fine sand 95 0.011 2219.82 2121.34 20
157
Table B-23 Test results of borehole BH-I0, Block-F, Plot-600 & 601 (Bashundhara)
Depth SPT-N Soil description F, D50 PI(m) (%) (mm)1.52 3 Silty clay3.66 26.71 I 99 0.0098.23 4 2810.67 1412.20 1512.80 2813.72 2615.24 2216.77 21 Clayey silt with18.29 22 trace fine sand19.82 2121.34 2122.87 2324.39 2325.91 2827.44 28 91 0.010
Table B-24 Test results of borehole BH-II, Block-F, Plot-600 & 601 (Bashundhara)
Depth SPT-N Soil description F, D50 PI(m) (%) (mm)1.52 3 Silty clay3.66 2 97 0.0106.71 28.23 810.67 1012.20 1212.80 1313.72 18 97 0.010 2715.24 1916.77 19 Clayey silt with18.29 19 trace fine sand65.00 20
Table B-25 Test results of borehole BH-12, Block-F, Plot-600 & 601 (Bashundhara)
Depth SPT-N Soil description F, D50 PI(m) ( %) (mm)1.52 I Silty clay3.66 I6.71 2 99 0.0098.23 810.67 1212.20 1312.80 1713.72 1715.24 2216.77 18 Clayey silt with 93 0.012 2118.29 20 trace fine sand
158
Table B-26 Test results of borehole BH-OI, Block-I, Plot-66 (Bashundhara)
Depth Soil description F, Dso PI(m) SPT-N (%) (mm)1.52 6 Loose sand-silt2.44 2 deposit.7.01 6 99 0.004 288.84 14 98 0.0089.76 1611.59 20 Silty clay13.72 21 95. 0.01015.24 2016.77 1917.68 1618.29 16
Table B-27 Test results of borehole BH-02, Block-I, Plot-66 (Bashundhara)
Depth SPT-N Soil description F, Dso PI(m) (%) (mm)1.52 5 Loose sand-silt4.27 I deposit 18 0.1499.15 12 Silty clay9.76 1512.80 22 97 0.008 2713.72 22 Silty clay with15.24 19 trace fine sand16.77 17 98 0.00718.29 16
Table B-28 Test results of borehole BH-03, Block-I, Plot-66 (Bashundhara)
Depth SPT-N Soil description F, Dso PI(m) ( %) (mm)1.52 22.44 6 Loose sand-silt6.71 12 deposit. 19 0.1358.54 18 Silty clay.12.80 15 95 0.01013.72 2115.24 23 98 0.009 2716.77 1918.29 18
159
Table B-29 Test results of borehole BH-04, Block-I, Plot-66 (Bashundhara)
Depth SPT-N Soil description F, D,o PI(m) (%) (mm)1.52 3 Loose sand-silt5.18 2 deposit. 20 0.14410.37 12 Siltv c1av.11.59 1613.72 18 96 0.009 2614.63 23 Silty clay with15.24 22 trace fine sand.16.77 2117.99 1818.29 1919.82 2221.34 22 Silty clay22.87 2425.91 28 97 0.01027.44 28
Table B-30 Test results of borehole BH-OI, Block-I, Plot-178A (Bashundhara)
Depth SPT-N Soil description F, D,o PI(m) (%) (mm)1.22 9 Brownish grey2.13 15 to grey fine3.05 18 sand with trace3.96 '13 silt4.88 156.40 157.93 16 90 0.0079.45 2210.98 9 Dark grey fine 15 0.200
sand with siltand trace mica
12.50 15 Brown silt with 92 0.006 16clay, trace fine
sand
Table B-31 Test results of borehole BH-02, Block-I, Plot-178A (Bashundhara)
Depth SPT-N Soil description F, D,o PI(m) ( %) (mm)1.22 10 Brownish grey2.13 16 to grey medium3.05 12 fine sand with3.96 15--c trace silt4.88 106.40 107.93 89.45 7 10 0.15010.98 512.50 16 Brown silt with 7 0.152 15
clay, trace finesand
160
Table B-32 Test results of borehole BH-03. Block-I, Plot-I78A (Bashundhara)
Depth SPT-N Soil description F, D50 PI(m) ( %) (mm)1.52 4 Grey fine sand,2.29 3 trace silt, trace 5 0.2203.20 3 mica4.12 35.03 55.95 77.62 109.15 1410.67 6 Grey clay, trace 91 0.005 2112.20 4 fine sand high
plastic13.72 32 Grey loose fine 21 0.125
sand, some silt15.24 31 Light brown16.77 27 fine sand, little 19 0.15018.29 31 silt trace mica
Table B-33 Test results of borehole BH-04, Block-I, Plot-178A (Bashundhara)
Depth SPT-N Soil description F, D,o PI(m) (%) (mm)1.52 5 Grey fine sand,2.29 3 little silt, trace 11 0.2503.20 2 mica4.12 .55.03 35.95 57.62 6 Grey fine sand, 6 0.1909.15 10 trace mica10.67 1012.20 713.72 16 Light brown 30 0.010
fine sand, somesilt trace mica.
15.24 22 Light brown16.77 40 fine sand, little 18 0.18018.29 40 silt, trace mica.
Table B-34 Test results of borehole BH-01, Block-G, Plot-936 (Bashundhara)
Depth SPT-N Soil description F, D,o PI(m) ( %) (mm)1.52 5 Light grey fine sand,2.29 5 trace silt3.20 54.12 65.03 56.55 5 9 0.1508.08 69.60 911.13 712.65 714.18 10 Light brown clayey silt 92 0.007 20
161
Table B-35 Test results of borehole BH-02, Block-G, Plot-936 (Bashundhara)
Depth SPT-N Soil description F, D50 PI(m) - (%) (mm)1.52 4 Light brown fine sand2.29 7 with trace silt3.20 74.12 7 10 0.1495.03 66.55 78.08 89.60 1011.13 1012.65 1214.18 12 7 0.14815.70 37 Brown fine sandy silt,17.23 38 trace clay 72 0.01718.75 50
Table B-36 Test results of borehole BH-03, Block-G, Plot-936 (Bashundhara)
Depth SPT-N Soil description F, D,o PI(m) (%) (mm)1.52 4 Light grey fine sand,2.29 5 trace silt3.20 74.12 65.03 76.55 88.08 89.60 7 10 0.14911.13 812.65 1014.18 13 Brown clayey silt 93 0.095 22
Table B-37 Test results of borehole BH-04, Block-G, Plot-936 (Bashundhara)
Depth SPT-N Soil description F, D" PI(m) ( %) (mm)
1.52 6 Light grey sand, trace silt2.29 53.20 54.12 65.03 66.55 78.08 69.60 611.13 5 8 0.15212.65 614.18 - 9 Light brown clayey silt15.70 1017.23 3918.75 35 Fine sandy silt, trace clay 71 0.04020.27 16 Brownish grey clayey silt
21.80 20
23.32 17 92 0.086 21
24.85 12
162
Table B-38 Test results of borehole BH.OI, Tenement Building No.-O I (Bashundhara)
Depth SPT-N Soil description F, D" PI(m) ( 'Yo) (mm)
1.52 8 Loose sand silt deposit4.27 4 8 0.1495.49 2 Silty clay 97 0.054 288.54 1310.67 14 Clayey silt12.20 1413.41 2813.72 29 Medium silt-sand15.24 37 deposit with trace clay16.77 46 81 0.02818.29 4819.82 4820.12 3322.87 40 Silty clay24.39 40
Table B-39 Test results of borehole BH-02, Tenement Building No.-O 1 (Bashundhara)
Depth SPT-N Soil description F, D" PI(m) ( 'Yo) (mm)1.52 8 Loose sand silt deposit 16 0.1404.27 1 98 0.007 297.01 15 Silty clay9.76 810.67 9 96 0.00612.20 10
Table B-40 Test results of borehole BH-03, Tenement Building NO.-OI (Bashundhara)
Depth SPT-N Soil description F, D" PI(m) ( 'Yo) (mm)1.52 7 Loose sand silt deposit4.27 2 15 0.1495.49 I Silty clay 99 0.007 278.54 12 97 0.06010.67 1112.20 10
Table B-41 Test results of borehole BH-04, Tenement Building NO.-Ol (Bashundhara)
Depth Si'T-N Soil description F, D" PI(m) ( 'Yo) (mm)1.52 6 Sand-silt deposit4.27 1 14 0.1645.49 1 Organic silty clay7.32 7 Silty clay 99 0.006 288.54 910.67 912.20 10 95 0.007
163
Table B-42 Test results of borehole BH-05, Tenement Building No.-01 (Bashundhara)
Depth SPT-N Soil description F, 0" pJ(m) (%) (mm)1.52 7 Sand silt deposit3.96 I 18 0.1505.18 I OrQanic silty clay6.71 3 Silty clay 98 0.006 279.76 13 96 0.00710.67 1612.20 18
Table B-43 Test results of borehole BH-06, Tenement Building No.-OI (Bashundhara)
Depth SPT-N Soil description F, 0'0 PI(m) (%) (mm)1.52 2 Silty clay2.44 44.27 2 Sand-silt deoosit 20 0.15010.06 8 Silty clav10.67 8 Clayey silt 93 0.062 2211.59 1812.20 1812.80 2313.72 25 Silt- sand deposit with 81 0.02515.24 26 trace clay16.16 4216.77 44 Silty clay18.29 4519.82 3122.87 38
24.39 38
Table B-44 Test results of borehole BH-07, Tenement Building No.-OI (Bashundhara)
Depth SPT-N Soil description F, 0'0 PI(m) (%) (mm)1.52 7 Silty1.83 7 Sand-silt deposit 17 0.1624.27 29.76 8 Silty clav 98 0.006 2610.67 8 Sand-silt deposit 80 0.02711.28 1012.20 10 Silty clay
Table B-45 Test results of borehole BH-08, Tenement Building No.-OJ (Bashundhara)
Depth SPT-N Soil description F, D,o PI(m) ( %) (mm)1.52 3 Silty clay1.83 32.44 55.18 4 Sand-silt deoosit 19 0.1556.71 3 Silty clay10.67 4 98 0.006 2611.28 1812.20 18
164
Table B-46 Test results of borehole BH-09, Tenement Building NO.-OI (Bashundhara)
Depth SPT-N Soil description F, D,o PI(m) (%) (mm)1.52 5 Sand-silt deposit1.83 54.27 2 9 0.1578.84 7 Silty clay 99 0.045 2810.67 811.59 1512.20 16 Clayey silt13.72 1715.24 1716.77 16 94 0.00617.99 5018.29 42 Silty clay19.82 4222.87 5024.39 50
Table B-47 Test results of borehole BH-IO, Tenement Building NO.-Ol (Bashundhara)
Depth SPT-N Soil description F, D,o PI(m) ( %) (mm)1.52 2 Silty clay1.83 55.18 3 Sand-silt deposit 20 0.1508.54 8 Silty clay 98 0.0059.76 1610.67 17 96 0.005 2712.20 18
Table B-48 Test results of borehole BH-II, Tenement Building NO.-OI (Bashundhara)
Depth SPT-N Soil description F, D,o PI(m) ( %) (mm)1.52 8 Sand-silt deposit1.83 4 17 0.1634.27 35.49 3 Oreanic silty clav 98 0.003 278.54 6 Silty clay10.67 7 97 0.00512.20 8
165
Table B-49 Test results of borehole BH-12, Tenement Building No.-Ol (Bashundhara)
Depth SPT-N Soil description F, D50 PI(m) ( %) (mm)1.52 5 Sand-silt deposit1.83 4 8 0.1494.27 38.54 8 Silty clay with trace 99 0.004 28
organic matter10.37 15 Silty clay10.67 17 Clayey silt12.20 1913.72 2015.24 2115.85 3416.77 37 Silt-sand deposit with18.29 39 trace clay 82 0.00419.21 3019.82 30 Silty clay22.87 45
24.39 45
Table B-50 Test results of borehole BH-OI, Tenement Building No.-06 (Bashundhara)
Depth SPT-N Soil description F, D,o PI(m) ( %) (mm)1.52 18 Grey fine sand with silt2.29 173.20 174.12 24 13 0.1605.03 126.55 I Grey silty clay, trace8.08 1 organic matter 98 0.005 289.60 311.13 6 Grey medium silty clay 95 0.010 2612.65 8
Table B-51 Test results of borehole BH-01, Tenement Building No.-07 (Bashundhara)
Depth SPT-N Soil description F, D50 PI(m) ( %) (mm)1.52 2 Grey silty clay trace2.29 2 occasional organic3.20 3 mater 98 0.004 284.12 25.03 36.55 38.08 1 99 0.004 289.60 111.13 4 Grey silt with clay, 92 0.01012,65 6 trace fine sand
166
Table 8-52 Test results ofboreltole BH-02, Tenement Building NO.-07 (Basltundhara)
Depth SPT-N Soil description F, D50 P\(m) (%) (mm)1.52 \ Grey clay) trace2.29 2 occasional organic3.20 2 matter4.12 \ 98 0.005 285.03 26.55 28.08 I9.60 \ 99 0.0052 2811.13 2\2.65 6 Grey clay, trace fine 91 0.0\
sand
Table B-53 Test results of borehole BH-2A, Tenement Building NO.-07 (Bashundhara)
Depth SPT-N Soil description F, D50 P\(m) ( %) (mm)1.52 \ Light brown to light2.29 I grey silty clay3.20 2 98 0.005 284.12 25.03 2 97 0.005 286.55 28.08 \ Dark grey organic silty9.60 \ clay 99 0.010
Table 8-54 Test results of borehole BH-03, Tenement Building NO.-07 (Bashundhara)
Depth SPT-N Soil de-scription F, D50 PI(m) (%) (mm)1.52 4 Grey fine sand with silt2.29 6 16 0.1493.20 24.12 \ Dark grey organic silty5.03 \ clay6.55 2 98 0.005 278.08 \9.60 \11.13 4 Bluish grey silty clay 96 0.007 27\2.65 7
Table 8-55 Test results of borehole BH-04, Tenement Building NO.-07 (Bashundhara)
Depth SPT-N Soil description F, D50 PI(m) ( %) (mm)1.52 4 Grey fine sand with silt2.29 53.20 3 18 0.1404.12 2 Grey sot silty clay,5.03 2 trace organic matter 99 0.006 276.55 28.08 29.60 211.\3 7 Bluish grey clay 95 0.009 2812.65 9
167
Table B-56 Test results of borehole BH-05, Tenement Building No.-07 (Bashundhara)
Depth SPT-N Soil description F, 0'0 PI(m) ( %) (mm)
1.52 3 Grey sand with silt2.29 33.20 3 19 0.1404.12 1 Dark grey clay trace5.03 1 organic matter6.55 I8.08 I9.60 2 Grey silty clay11.13 312.65 6 Brownish grey silty 97 0.009 2814.18 11 clay15.70 15 Light brown clayey silt,17.23 16 trace fine sand 92 0.013 2118.75 22 Light grey silty clay21.80 30
Table B-57 Test results of borehole BH-06, Tenement Building No.-07 (Bashundhara)
Depth SPT-N Soil description F, 050 PI(m) ( %) (mm)
1.52 4 Grey sand with silt2.29 4 17 0.1403.20 34.12 2 Dark grey trace organic5.03 2 matter6.55 1 Grey silty clay8.08 19.60 111.13 612.65 10 Brownish grey to light14.18 19 brown, clayey silt, trace15.70 21 fine sand 91 0.012 2217.23 1818.75 23 97 0.010 27
Table B-58 Test results of borehole BH-07, Tenement Building No.-07 (Bashundhara)
Depth SPT-N Soil description F, 0'0 PI(m) ( %) (mm)1.52 5 Grey fine sand, trace 7 0.1552.29 6 sand3.20 3 9 0.1504.12 1 Dark grey silty clay,5.03 I trace organic matter 276.55 I
168
Table B-59 Test results of borehole SH-OI (Purbachal New Model Town)
Depth SPT-N Soil description Gs We F, Dso PI(m) (%) (%) (mm)
0.91 8 Gray silty fine sand 14.06 II 0.195 143.05 8 2.69 15.74 13 0.200 03.66 12 Clay 264.57 13 256.1 10 147.62 21 Gray silty fine sand 2.58 11.28 36 0.1409.15 18 2.65 13.46 36 0.09010.67 23 2.63 23.04 44 0.08012.2 30 2.66 18.38 26 0.17013.72 34 2.67 17.4 I 26 0.17015.24 35 14.17 25 0.17016.77 50 12.69 27 0.175
Table B-60 Test results of borehole SH-02 (Purbachal New Model Town)
Depth SPT-N Soil description Gs We F, Dso PI(m) (%) ( %) (mm)
1.52 5 Brown silty fine sand 16.19 12 0.2003.05 0' 4 2.7 15.9 6 0.3204.57 I Clay 166.1 3 167.62 5 Silty sand 2.63 19.28 34 0.1609.15 6 2.67 17.97 33 0.13010.67 12 15.04 21 0.17012.2 12 12.07 25 0.20013.72 13 2.62 19.09 39 0.08715.24 15 16.85 33 0.11016.77 16 12 0.18018.29 15 14.32 27 0.180
Table B-61 Test results of borehole SH-03 (Purbachal New Model Town)
Depth SPT-N Soil description Gs We F, Dso PI(m) (%) ( %) (mm)
1.52 1 Silty sand 2.66 16.68 18 0.2203.05 2 2.68 14.13 16 0.1804.57 I 21.96 22 0.1706.10 2 Clay I I7.62 4 329.15 10 Silty sand 2.61 17.02 38 0.10010.67 10 2.68 20.27 31 0.13012.2 13 13.35 0.34013.72 15 2.68 13.64 28 0.17015.24 24 33 0.09516.77 26 2.7 16.34 57 ---18.29 31 13.42 29 O.I 7019.82 33 8.46 30 0.180
169
Table B-62 Test results of borehole BH-OI (Uttara third phase)
Depth SPT-N Soil description Gs w" F, Dso PI(m) ('Yo) ( 'Yo) (mm)1.52 3 Grey silty fine sand 2.64 18.22 10 0.1803.05 10 2.71 26.12 33 0.0954.57 I Clay 256.1 0 147.62 I9.15 3 1010.67 2 1712.2 2 1413.72 13 3915.24 14 2516.77 9 3318.29 10 1819.82 14 12
Table B-63 Test results of borehole BH-02 (Uttara third phase)
Depth SPT-N Soil description Gs w" F, D,o PI(m) ('Yo) ('Yo) (mm)1.52 7 Silty fine sand 14.23 5 0.2503.05 8 15.31 II 0.1904.57 3 16.59 5 0.2106.10 3 2.71 22.76 18 0.1307.62 4 2.71 17.32 I 1 0.1909.15 2 2.7 18.35 13 0.21010.67 2 Clay 1712.20 10 1413.72 12 2415.24 16 1716.77 918.29 9
Table B-64 Test results of borehole BH-03 (Uttara third phase)
Depth SPT-N Soil description Gs w" F, D,o PI(m) ('Yo) ('Yo) (mm)1.52 6 Silty fine sand 2.71 14.24 12 0.2103.05 3 2.73 16.59 12 0.2304.57 . 3 14.22 56 ---6.1 4 19.56 17 0.1707.62 4 2.73 24.28 23 0.2209.15 5 272 22.7 42 0.08510.67 9 Clay 2.67 1512.2 7 1713.72 13 1615.24 I I 1516.77 12
170
Table B-65 Test results of bore hole, BH-04 (Uttara third phase)
Depth SPT-N Soil description Gs w, F, D50 PI(m) (%) ( %) (mm)1.52 3 Silty fine sand 2.71 8 0.2003.05 2 2.73 9 0.1704.57 5 Clay 315.49 7 296.1 77.62 11 299.15 7 1210.67 812.2 713.72 715.24 7 1316.77 7 2118.29 8 16
Table 8-66 Test results of borehole BH-05 (Uttara third phase)
Depth SPT-N Soil description Gs w" F, D50 PI(m) (%) (%) (mm)1.52 3 Silty fine sand 15.71 14 0.1803.05 3 2.64 21.63 10 0.1804.57 2 41 0.1005.18 2 Clay 177.62 4 139.15 8 3010.67 912.2 1513.72 16 4015.24 12 Silty fine sand 39 0.10516.77 14 23 0.12018.29 21 2.63 14.16 27 0.180
Table 8-67 Test results of borehole BH-06 (Uttara third phase)
Depth SPT-N Soil description Gs w, F, D50 PI(m) (%) (%) (mm)1.52 2 Silty fine sand 2.68 20 6 0.1803.05 - 2 2.66 19 9 0.2004.57 2 19 2 0.2606.1 I 34 0.1007.62 0 Clay 439.15 6 -10.67 7 2812.2 8 silty fine sand 13 39 0.12013.72 10 37 0.09715.24 10 33 0.09816.77 11 21 25 0.20018.29 13 13 26 0.200
171
Table B-68 Test results of borehole BH-OI, Road-02, Plot-325 (Mirpur DOHS)
Depth SPT-N Soil description Gs w, Ydcy F, Dso PI q, or eo <I>(m) - ('Yo) (kNlm3
) ('Yo) (mm) (kPa) ('Yo) (D)
1.00 25 Red plastic clay 16.812.00 30 23 349.63.00 35 99 0.008 264.50 356.00 18 Brown silt with7.50 9 trace clay and 2.60 92 0.0309.00 14 trace fine sand10.50 19 Brown fine
sandy silt withtrace mica
12.00 24 Brown silty 27 0.17013.50 27 fine sand with15.00 32 trace mica 29.5
Table B-69 Test results of borehole BH-02, Road-02, Plot-325 (Mirpur DOHS)
Depth SPT-N Soil Gs w, Ydcy F, Dso PI q, $0 eo C,(m) description ('Yo) (kN/m3
) ( 'Yo) (mm) (kPa)
1.00 20 Red plastic -2.00 24 clay -3.00 27 2.64 24 16.5 327.8 0.63 0.084.50 26 - 99 0.007 256.00 16 -7.50 9 Brown silt with -9.00 13 trace clay -10.50 18 Fine sandy silt - 72 0.04512.00 23 Brown silty -13.50 28 fine sand with 2715.00 33 trace mica 2.67 26 0.160
Table B-70 Test results of borehole BH-03, Road-02, Plot-325 (Mirpur DOHS)
Depth SPT-N Soil Gs w, Ydcy F, Dso PI q, $0(m) description ('Yo) (kN/m3
) ( 'Yo) (mm) (kPa)
1.00 20 Red plastic 16.292.00 25 clay 25 2983.00 274.50 286.00 13 100 0.010 237.50 10 Brown silt with9.00 14 trace clay 2.64 66 0.04510.50 17 Brown fine 25.8
sandy silt withtrace mica
12.00 25 Brown silty13.50 30 fine sand 24 0.20015.00 31
172 J,
Table B.7ITest results of borehole BH-04, Road-02, Plot-325 (Mirpur DOHS)
Depth SPT-N Soil description Gs w, Yd'Y F, D50 PI q, $' eo C,(m) (%) (kN/m3
) (%) (mm) (kPa)
1.00 28 Red plastic2.00 29 clay 17.043.00 29 2.65 23 344 0.6 0.074.50 31 100 0.006 286.00 147.50 11 Brown clay and 90 0.Q259.00 17 trace fine sand10.50 20 Brown fine 2.65 30 0.15012.00 24 sandy silt with
trace mica13.50 28 Brown silty15.00 30 fine sand 29.3
Table B-72 Test results of borehole BH-01, Road-02, Plot-333 (Mirpur DOHS)
Depth SPT-N Soil description Gs w, Yd'Y F, D50 PI q, $' eo C,(m) (%) (kN/m3
) (%) (mm) (kPa)
1.00 1 Gray silty fine2.00 1 sand with trace3.00 2 mica4.50 26.00 4 Sandy silt 100 0.007 277.50 5 Medium stiff9.00 9 clay 91 0.02210.50 16 Silt with sand12.00 20 Brown medium 2.66 68 0.05013.50 24 dense fine sand15.00 34 Silt with mica16.50 35 Brown silty 23 0.15018.00 26 fine sand with 28.319.50 25 trace mica
Table B-73 Test results of borehole BH-02, Road-02, Plot-333 (Mirpur DOHS)
Depth SPT-N Soil description Gs w, Yd'Y F, D50 PI q, $' eo C,(m) (%) (kN/m3
) ( %) (mm) (kPa)
1.00 2 Gray to brown2.00 2 s.ilty fine sand3.00 3 with trace mica 2.64 27 129 0.73 0.144.50 11 Red stiff high 15.44 246.00 13 plastic clay7.50 5 91 0.0139.00 6 Silt with trace10.50 12 fine sand 80 0.03712.00 18 Brown fine13.50 20 sand silt with15.00 27 trace mica 29.516.50 3218.00 24 Brown silty 29 0.14019.50 25 fine sand with 26.721.00 27 trace mica22.50 32 2.68 20 0.180
173
Table B-74 Test results of borehole BH-03, Road-02, Plot-333 (Mirpur DOHS)
Depth SPT- Soil description Gs w, Yd<y F, D,o PI q" ~o eo C,(m) N (%) (kN/mJ
) (%) (mm) (kPa)
1.00 2 Gray silty fine2.00 2 sand with trace 16.77
mica3.00 23 Red plastic clay 24 2394.50 21 98 0.007 256.00 11 2.63 94 0.0167.50 10 Stiff silt with
trace fine sand9.00 9 Silt trace fine10.50 13 - sand 79 0.03812.00 22 Reddish brown13.50 25 silty fine sand 28.515.00 30 with trace mica 2.67 25 0.17016.50 3418.00 3019.50 29
Table B- 75 Test results of borehole BH-04,Road-02, Plot-333 (Mirpur DOHS)
Depth SPT-N Soil description Gs w, Yd<y F, D,o PI q" ~o eo C,(m) (%) (kN/mJ) ( %) (mm) (kPa)
1.00 2 Gray very loose2.00 2 silty fine sand 15.273.00 10 Red stiff to 2.62 27 116 0.77 0.184.50 18 very stiff high6.00 9 plastic clay 96 0.007 157.50 10 Stiff clavev silt9.00 13 Silt with trace 78 0.04210.50 16 fine sand
12.00 20Silt with somefine sand
13.50 23 44 0.10015.00 31 Brown silty16.50 32 fine sand with 31.518.00 25 trace mica 2.66 26 0.17019.50 27
174
Table B-76 Test results of borehole BH-05, Road-02, Plot-333 (Mirpur DOHS)
Depth SPT-N Soil description Gs F, D50 PI <1>0(m) (%) (mm)
1.00 1 Gray silty fine sand2.00 2 with trace mica3.00 24.50 2 Silt with trace clay &6.00 7 trace brick chips7.50 6 Stiff clayey silt 97 0.007 199.00 1110.50 18 Silt with trace sand12.00 21 Brown fine sand silt 68 0.07513.50 23 with trace mica15.00 36 Brown fine sand & 2.7 21 0.22016.50 30 silt with trace mica18.00 29 29.319.50 3021.00 31 26 0.18022.50 33 31.0
Table B-77 Test results of borehole BH-OI, Road-02, Plot-349 (Mirpur DOHS)
Depth SPT-N Soil description Gs w, Ydry F, D50 PI q, <1>0(m) (%) (kN/mJ) ( %) (mm) (kPa)
1.00 5 Gray loose silty2.00 3 fine sand3.00 1 34 27.64.50 2 13.386.00 3 Black very 100 0.011 20
organic clay7.50 2 Red clayey silt9.00 210.50 3 Black soft 2.62
organic clav13.00 4 Brown clayey 100 0.02014.50 5 silt 25.816.00 2017.50 27 Brown 67 0.05019.00 21 micacious fine20.50 29 sandy silt
175
Table B-78 Test results of borehole BH-02, Road-02, Plot-349 (Mirpur DOHS)
Depth SPT-N Soil description Gs We Yd'Y F, D,o PI q, ~o eo C,(m) (%) (kN/m') (%) (mm) (kPa)
1.50 4 Brown silty3.00 2 fine sand 2.59 35 23.9 l.l 0.244.50 1 13.266.00 2 Red clayey silt 97 0.008 187.50 39.00 4 100 0.005 2410.50 3 Block clayey12.00 5 silt13.50 16 Gray soft15.00 17 plastic clay17.50 19 33 0.14018.00 2519.50 26 Brown dense21.00 30 silt with trace 29.5
mica22.50 32 Brown silty24.00 35 fine sand with 2.67 69 0.05025.50 40 trace mica
Table B-79 Test results of borehole BH-03, Road-02, Plot-349 (Mirpur DOHS)
Depth SPT-N Soil description Gs We Yd'Y F, D,o PI q, ~o eo C,(m) (%) (kN/m') ( %) (mm) (kPa)
1.50 3 Gray silty fine3.00 4 33 96 0.009 15 29.44.50 2
sand13.60
6.00 2Red soft7.50 2
9.00 3clayey silt
10.50 5 I .Clayey silt with 2.61 91 0.03012.00 7 trace organic13.50 14
Brown silt with15.00 16 71 0.04617.50 18
trace fine sand& trace mica
18.00 1819.50 21 Sandy silt with21.00 25 trace mica 26 0.17022.50 30 Brown silty24.00 31 fine sand with 3225.50 41 trace mica
176
Table B-80 Test results of borehole BH-04, Road-02, Plot-349 (Mirpur DOHS)
Depth SPT-N Soil description Gs w, Yd'Y F, D,o PI q, $0 eo C,(m) (%) (kN/m') (%) (mm) (kPa)
1.50 IGray silty fine3.00 I sand4.50 2 2.62 32 13.77 , 35.1 1.01 0.26
6.00 2 Red to grayish7.50 3 brown & gray 100 0.009 209.00 2 clayey silt 90 0.03410.50 2 Brown silt with
12.00 4 trace fine sand& trace mica
13.50 14 68 0.05015.00 16
Brown fine17.50 20sandy silt with18.00 25 trace mica 26.3
19.50 2121.00 2722.50 30 Brown silty fine 2.66 35 0.16024.00 33 sand with trace25.50 42 . mica
Table B-81 Test results of borehole BH-Ol, Road-IO, Plot-211 (Mirpur DOHS)
Depth SPT-N Soil description F, D,o(m) (%) (mm)I 18 Red plastic clay2 203 174.5 21 100 0.0076 207.5 89 10 Red silt with trace clay & 92 0.01810.5 10 trace fine sand12 1713.5 20 Red fine sandy silt with trace15 26 mica 74 0.055
Table B-82 Test results of borehole BH-02, Road-IO, Plot-211 (Mirpur DOHS)
Depth SPT-N Soil description F, D,o(m) ( %) (mm)I 21 Red very stiff high plastic clay2 223 234.5 216.0 16 100 0.0097.5 9 95 0.079.0 II Red silt with trace clay &
trace fine sand10.5 12 Red fine sandy SILT with12 18 trace mica 68 0.0513.5 2215 25
177
Table B-83 Test results of borehole BH-OI, MIST thesis (Mirpur DOHS)
Depth SPT-N Soil description Gs w, "(wet Yd'l' F, PI q, C ~o(m) (%) (kN/m3
) (kN/m3) (%) (kPa) (kPa)
l.00 I Red silty clay1.50 32.00 4 Brown silty 2.59 30 18.40 14.14 90 30 58 25 213.00 5 clay 2.60 774.50 4 Fine sandy silt6.00 12 Brown silty8.00 10 fine sand9.00 20 2.66 27 36.510.50 3213.00 3414.50 44 2.68 19 36.517.00 48
TableB-84 Test results of borehole BH-02, MIST thesis (Mirpur DOHS)
Depth SPT-N Soil description Gs w, Ywel Yd'l' F, PI q, C ~o(m) (%) (kN/m3
) (kN/m3) ( %) (kPa) (kPa)
l.00 4 Brown silty2.00 2 clay3.00 2 2.6 25 36.54.50 3 Clayey silt, 2.57 34 17.79 13.386.00 2 trace organic8.00 5 Gray clayey silt9.00 9 2.64 74 2410.50 17 Sandy silt12.00 31 Brown silty13.50 34 fine sand 2.67 24 3115.00 40
Table B-85 Test results of borehole BH-03, MIST thesis (Mirpur DOHS)
Depth SPT-N Soil description Gs w, 'Ywct Yd<y F, PI q, C ~o(m) (%) (kN/m3
) (kN/m3) ( %) (kPa) (kPa)
l.00 15 Red silty clay 28 992.00 22 2l.30 16.86-3.00 23 2.62 100 234.50 206.00 15 Red clayey silt,7.50 14 trace fine sand 93 16 26.49.00 910.50 14 Fine sandy silt12.00 23 2.66 29.514.00 30 Brown compact15.50 34 to dense silty
fine sand
178
. ,
Table B-86 Test results of borehole BH-04, MIST thesis (Mirpur DOHS)
Depth SPT-N Soil description Gs w, "(wet Yd'Y F, PI q" C $0(m) (%) (kN/m') (kN/m') ( %) (kPa) (kPa)
1.00 II Red silty clay2.00 24 2.62 26 98.63.00 26 20.40 16.504.00 285.50 25 2.64 74 237.00 268.50 12 Brown clayey10.00 16 silt, trace fine11.00 33 sand12.50 34 Brown silty 2.67 27 3114.00 36 fine sand 2.67 21 32
Table B-87 Test results of borehole BH-05, MIST thesis (Mirpur DOHS)
Depth SPT-N Soil Properties Gs w, "(wet Yd'Y F, PI q" C $0(m) (%) (KN/m') (KN/m') (%) (kPa) (kPa)1.00 6 Red silty clay2.00 53.00 4 2.6 314.00 3 35 18.01 13.35 66.85.50 37.00 28.50 210.00 3 Black11.50 4 decomposed13.00 4 wood14.50 516.00 13 2.64 7617.50 24 Fine sandy silty18.50 34 Silty fine sand20.00 40 2.68 18
Table B-88 Test results of borehole BH-06, MIST thesis (Mirpur DOHS)
Depth SPT-N Soil description Gs F, $0(m) ( %)1.00 2 Brown silty2.00 I clay3.00 2 Brown silt,4.50 3 some sand, 2.62 826.00 4 trace clay7.50 149.00 18 Fine sandy silt,10.50 17 trace mica12.00 19 Brown silty13.50 21 fine sand, trace 2.68 25 26.715.00 22 mica16.50 2318.00 2519.50 31 2.66 43 34
179
Table B-89 Test results of borehole BH-07, MIST thesis (Mirpur DOHS)
Depth SPT-N Soil description Gs w, Ywet Yo", F, D,o PI q" ~o
(m) (%) (kN/m') (kN/m') (%) (mm) (kPa)1.00 1 Grey clayey silt2.00 I3.00 24.50 2 33 17.90 13.10 36.56.00 37.50 3 .9.00 2 2.57 96 1510.50 312.00 313.50 S SillY fine sand 2.66 32 0.01215.00 13 Grey silty clay16.50 21 2.6S 40 23IS.00 2419.50 25 SillY fine sand 2.6S 24
Table B-90 Test results of borehole BH-OS, MIST thesis (Mirpur DOHS)
Depth SPT-N Soil description Gs w, Ywel Yd", F, D,o PI q" ~o(m) (%) (kN/m') (kN/m') (%) (mm) (kPa)1.00 2 Grey clayey2.00 2 silt, trace3.00 I organic4.50 I IS.76 14.10 40.36.00 2 Black7.50 2 decomposed9.00 I wood10.50 2 Grey clayey 2.63 100 IS12.00 2 silt, trace13.50 9 organic15.00 15 Silty fine sand,16.50 16 trace clay ballsIS.00 IS Grey silty clay19.50 1421.00 IS22.50 29 Grey silty fine24.00 32 sand, trace 2.64 23 0.170 32
mica
180
Table B-91 Test results of borehole BH-OI, Masjid Road, Plot-I04 (Banani Old DOHS)
Depth SPT-N Soil description Gs w, Yd", F, D" PI go $' eo C,(m) (%) (kN/m') ( %) (mm) (kPa)
I 3 Red silt withtrace clay &
trace brick chips2 14 Red plastic clay 2.65 24 16.41 22.1 0.69 0.143 174.5 21 100 0.007 286 I I 91 0.0257.5 10 Brown silt with
some clay &trace fine sand
9 12 Brown fine10.5 18 sandy silt with
trace mica12 26 Brown silty fine 2.66 23 0.18013.5 31 sand15 35 31.5
Table B-92 Test results of borehole BH-02, Masjid Road, Plot-I04 (Banani Old DOHS)
Depth SPT-N Soil description Gs w, Yd", F, D" PI go $' eo C,(m) (%) (kN/m') ( %) (mm) (kPa)
1 5 Red medium & 28 112 II lastic clay 15.223 18 294.5 226 117.5 10 Brown silt clay
& trace fine9 8 Brown silty 2.64
10.5 18 fine sand12 21 27.313.5 3115 34
Table B-93 Test results of borehole BH-03, Masjid Road, Plot-I04 (Banani Old DOHS)
Depth SPT-N Soil description Gs w, Yd", F, D" PI go $' eo C,(m) (%) (kN/m') (%) (mm) (kPa)
I 9 Red plastic clay2 11 2.6 26 15.95 18.7 0.73 0.173 204.5 216 107.5 11 Silt with clay & 92 0.0119 17 trace fine sand10.5 21 Brown silty fine 27 0.14012 23 sand13.5 31 29.515 33 2.67 27 19 0.200 14
181
Table B-94 Test results of borehole BH-04, Masjid Road, Plot-l04 (Banani Old DOHS)
Depth SPT-N Soil description Gs w, Yd'Y F, D" PI q, ~o eo C,(m) (%) (kN/m') ( %) (mm) (kPa)
1 5 Red medium 27 142 13 plastic clay 15.553 204.5 21 100 0.009 236 137.5 12 Silt with trace
fine sand9 15 Silt with trace 2.66 44 0.10010.5 22 fine sand 25.812 24 Brown se silty 2.6613.5 32 fine sand 26 0.190 17.915 36
Table B-95 Test results of borehole BH-05, Masjid Road, Plot-I04 (Banani Old DOHS)
Depth SPT-N Soil description Gs w, Yd'Y F, D" PI q, ~o eo C,(m) (%) (kN/m') (%) (mm) (kPa)
I 10 Red medium .
2 10 plastic clay 25 16.12 17.93 164.5 20 100 0.0076 12
7.5 10 Silt with trace92 0.017fine sand
9 13 Silt with trace10.5 16 fine sand 25.812 22 Brown se silty 23 0.21013.5 28 fine sand15 32 2.66
Table B-96 Testresults of borehole BH-OI, Block-A, Plot-15 (Banasree)
Depth SPT-N Soil description Gs w, Yd'Y F, D" PI q, or eo C,(m) (%) (kN/m') (%) (mm) (kPa) (%)
1.52 I Soft clay 942.74 1 47 12 26 20 43.66 2 Block, soft, high7.01 3 plastic, fat clay 269.76 2 Dark gray to13.72 2 bluish gray to 59 2415.24 3 yellowish16.77 3 brown, soft,18.29 10 high plastic,19.82 17 lean clay21.34 18 99 2422.87 16 Sandy silt, trace24.39 50 mica 52
182
Table B-97 Test results of borehole BH-02, Block-A, Plot-15 (Banasree)
Depth SPT-N Soil description Gs w, Yd'Y F, D,o PI q" or C <po(m) ('Yo) (kN/m') ( 'Yo) (mm) (kPa) ('Yo) (tsf)
1.52 2 Brown, loose, 123.05 3 silty sand, trace 45 0.120 124.57 3 mica 126.10 5 Dark gray, soft, 0.3 127.62 2 high plastic, 219.15 4 lean clay10.67 9 Brown, medium12.20 18 dense, silty 24 0.26013.72 20 sand, trace mica15.24 14 Bluish gray to16.77 15 grayish light 2118.29 17 brown, firm, 92 --19.82 18 high plastic,21.34 19 lean clay 1922.87 1724.39 12 Brownish black25.91 10 organic clay 77 --
Table B-98 Test results of borehole BH-03, Block-A, Plot-I 5 (Banasree)
Depth SPT-N Soil description Gs w, Yd'Y F, D,o PI q" Of C <po(m) ('Yo) (kN/m') ('Yo) (mm) (kPa) ('Yo) (tsf)1.52 2 Brown, 42 0.180 123.05 2 Loose Silty 124.57 2 sand, 126.10 3 trace mica 127.62 2 Soft clay 239.15 210.67 13 Silty sand,12.20 17 trace mica 32 0.15013.72 21 Clay15.24 12 Brown to dark 2316.77 16 gray plastic18.29 27 lean clay 45 0.10019.82 1521.34 1922.87 20 92 --24.39 13 Silty sand, trace 1625.91 14 mica
I183
Table B-99 Test results of borehole BH-04, Block-A, Plot-15 (Banasree)
Depth SPT-N Soil description Wn 'Ywct Ydcy F, PI C q, Er(m) (%) (kN/m') (kN/m') ( %) (tst) (kPa) (%)1.52 2 Brown to 22 0.123.05 2 blackish gray 47 17.27 11.61 95 0.12 27.50 44.57 2 0.126.10 2 Bluish gray to 0.127.62 1 brown to9.15 2 grayish light 9210.67 I I brown 2212.20 1213.72 1015.24 II High to 8916.77 15 medium plastic18.29 16 lean clay 2419.82 1621.34 2222.87 20 8524.39 23 15
Table B-100 Test results of borehole BH-05, Block-A, Plot-15 (Banasree)
Depth SPT-N Soil description F, Dso PI C $0(m) (%) (mm) (tst)1.52 2 Grayish light brown, 0.19 123.05 3 Loose Silty sand, trace mica 45 0.100 124.57 2 126.10 3 237.62 1 Black to bluishish gray,9.15 4 plastic, lean clay,10.67 3 Yellowish gray, silty sand, 59 -12.20 15 trace mica13.72 10 Gray spotted brown, high
plastic, lean clav15.24 18 Dark brown, silty sand, trace 92 - 2216.77 17 mica18.29 2419.82 26 35 0.18021.34 30
Table B-101 Test results of borehole BH-OI, Block-E, Road-02, Plot-04 (Banasree)
Depth SPT-N Soil description Gs rdcy F, D50 PI q, eo C,(m) (kN/m') ( %) (mm) (kPa)1.00 4 Fine sand & silt2.00 5 with trace mica 2.6 59 0.06 21 1.8 0.4313.00 1 Gray clayey silt4.50 26.00 27.50 2 12.89 339.00 4 2210.50 312.00 413.50 18 Fine sandy silt 67 0.00515.00 29 Silty fine sand16.50 28 32 0.01118.00 35 Grey clayey silt19.50 38 with trace fine sand
184
Table B-I02 Test results of borehole BH-02, Block-E, Road-02, Plot-04 (Banasree)
Depth SPT-N Soil description Gs w, Yd", F, 0'0 PI q,(m) (%) (kN/m') (%) (mm) (kPa)
1.00 3 Grey fine sand &2.00 2 silt with trace3.00 3 mica 53 0.0074.50 26.00 3 Grey clayey silt7.50 4 Grey clayey silt 96 0.0029.00 3 with trace organic10.50 3 2.63 39.82 12.91 25 3212.00 4 Grey clayey silt13.50 1315.00 25 . Grey silty fine16.50 33 sand with trace18.00 30 mica19.50 33 29 0.014
Table B-I03 Test results of borehole BH-03, Block-E, Road-02, PIot-04 (Banasree)
Depth SPT-N Soil description Gs w, Ywet Yd", F, 0'0 PI q,(m) (%) (kN/m') (kN/m') (%) (mm) (kPa)
1.00 2 Grey silt & fine2.00 2 sand3.00 34.50 2 Decomposed6.00 3 wood 96 0.0037.50 4 Gray clayey silt 35.18 18.04 13.36 21 429.00 410.50 312.00 13 Grey silty fine13.50 11 sand with trace 2.62 31 0.01215.00 17 mica16.50 2318.00 2819.50 40 Silty fine sand 41 0.009
Table B-104 Test results of borehole BH-OI, Main Road, Plot-H-Ol (Banasree)
Depth SPT-N Soil description Gs w, Ywel Yd", F, 0'0 PI $0 q,(m) (%) (kN/m') (kN/m') ( %) (mm) (kPa)
1.00 3 Gray silty fine2.00 1 sand3.00 2 Clayey silt with 96 0.009 184.50 2 trace organic 37 17.83 13.01 23.86.00 67.50 7 Gray clayey silt9.00 1110.50 II Brown plastic12.00 10 clay 2.63 100 0.00813.50 1015.00 1716.50 2218.00 31 Brown fine 71 0.05019.50 34 sandy silt with 29.3
trace mica
185
Table B-I05 Test results of borehole BH-02, Main Road, Plot-H-Ol (Banasree)
Depth SPT-N Soil description Gs w" 'Ywet Yd'Y F, D,o PI <1>0 qo(m) ('Yo) (kN/m') (kN/m') ( 'Yo) (mm) (kPa)
1.00 4 Gray clayey silt2.00 2 33.5 31.23.00 2 Gray to brown 17.95 13.444.50 2 clayey silt6.00 4 Back soft7.50 3 decomposition9.00 4 wood 2.61 100 0.00910.50 10 Grav clayey silt12.00 14 Gray to brown13.50 17 plastic clay15.00 19 100 0.005 2316.50 2018.00 33 Gray fine sandy 31.519.50 34 silt with trace21.00 35 mica 67 0.050
Table B-I06 Test results of borehole BH-03, Main Road, Plot-H-OI (Banasree)
Depth SPT-N Soil description Gs w" Ywct= 1d" F, D50 PI <1>0 q, eo C,(m) (%) (kN/m') (kN/m') (%) (mm) (kPa)
1.00 2 Gray to brown2.00 2 clayey silt3.00 2 80 0.009 154.50 2 Clayey silt with 2.59 36 17.89 13.17 23.1 1.11 0.316.00 3 trace organic7.50 4 Gray clayey silt9.00 410.50 812.00 II Medium plastic 66 0.00813.50 13 clay15.00 1516.50 1818.00 21 100 0.05019.50 30 Silty fine sand 2.65821.00 32 with trace mica 29.5
186
Table B-I07 Test results of borehole BH- 01, Kholamora, Keraniganj
Depth SPT-N Soil description F, D" PI(m) (%) (mm)1.52 10 Sandy 12 0.193.05 34.57 5 Silty clay6.10 27.62 2.9.15 410.67 II Sandy12.20 613.72 32 10 0.2215.24 18 20 0.1316.77 16 Sandy silt 31 0.0918.29 2519.82 33 Sand 22 0.1121.34 40 14 0.1822.87 36 16 0.1824.39 38 9 0.3
Table B-I08 Test results ofberehole 02, Kholamora, Keraniganj
Depth SPT-N Soil description F, D"(m) (%) (mm)1.52 2 Sand 15 0.183.05 1 6 0.394.57 4 II 0.376.10 4 Silty sand7.62 3 Sandy silt9.15 3 Sillv sand10.67 27 Sand 18 0.1712.20 19 18 0.1813.72 21 19 0.2115.24 21 Silty sand16.77 1818.29 41 17 0.3519.82 31 Sandy 19 0.1321.34 39 13 0.1922.87 41 22 0.2324.39 44 13 0.18
187
