PROFILING AND ZONING OF GEOTECHNICAL SUB-SOIL DATA USING GEOGRAPHIC INFORMATION SYSTEM · 2016-01-25 · PROFILING AND ZONING OF GEOTECHNICAL SUB-SOIL DATA USING GEOGRAPHIC INFORMATION

Sci.Int (Lahore), 25(4),531-537, 2013 ISSN 1013-5316; CODEN: SINTE 8 531

PROFILING AND ZONING OF GEOTECHNICAL SUB-SOIL DATA USING GEOGRAPHIC INFORMATION SYSTEM

Mahmood Ahmad*, Qaiser Iqbal and Fayaz Ahmad Khan Department of Civil Engineering, University of Engineering and Technology Peshawar, Pakistan

*Contact: [email protected]

ABSTRACT: This research paper presents a compendium of the geotechnical sub-soil data profiling and

zoning of the major urban settlements of Peshawar using Geographic Information System. Significant

geotechnical properties of the under study area soils i.e., Zone 5 & 6 in Peshawar were assessed through

one hundred and three different standard penetration test reports up to the depth of 1 m and 3 m. The

qualitative description of the sub-soil data was manipulated into the quantitative figures by means of

coding in order to interpolate the soil class distribution for the preparation of geotechnical zonation maps.

This work is helpful for balancing of cost and acquiring the significant reliable data regarding soil class

distribution, classification charactrestics, shear strength charactrestics and bearing capacity of soils

during feasibility and preliminary design stage of the project.

Keywords: Geotechnical properties, Geotechnical zonation maps, Interpolation and Urban settlements.

List of symboles/abbrevations

CL-ML Silty Clay or Clayey Silt

CL Clay

c Cohesion or Inter-Particle Attraction

DEM Digital Elevation Model

GZMs Geotechnical Zonation Maps

GIS Geographic Information System

GW Well Graded Gravel

GP Poorly Graded Gravel GC Clayey Gravel

GTS General Topographic Sheet

GPS Global Positioning System

GM Silty Gravel

IDW Inverse Distance Weighted Interpolation

LL Liquid Limit of Soil

ML Silt

NSL Natural Surface Level

PL Plastic Limit of Soil

PI Plastic Index of Soil = LL – PL

PCF Pounds per Cubic Foot

SPT Standard Penetration Test SP Poorly Graded Sand

SM Silty Sand

SRTM Shuttle Radar Topographic Mission

TSF Tons per Square Foot

USCS Unified Soil Classification System

ϕ Angle of Internal Friction

1. INTRODUCTION The profiling and zoning of geotechnical sub-soil data is

often considered as one of the very important information

for the planning and a construction projects in civil engineering works. Data availability can cut the expense of

the projects and also reduce time, particularly during

feasibility and planning stage. In past few years, the numbers

of construction projects in Peshawar have increased rapidly.

Consequently, the number of soil boring reports has been

accrued largely. The presentation of already available sub-

soil data in a user friendly format will enable the geo-

technical and civil engineers beforehand to plan the detail

geotechnical investigation based on the provided soil profile

and Geotechnical Zonation Maps (GZMs). The GZMs and

sub-soil profile will facilitate the geotechnical engineers for

preliminary design of foundations, feasibility study and

preparation of rough cost estimates for the proposed

projects. The geographic information system (GIS) is a

valuable tool for geotechnical engineers, not only for non-

data area prediction but also used to interpret the complex

data area with reliability and accuracy [1].

The GZMs have not yet been prepared by any group, agency or individual at Khyber Pakhtunkhwa level and this work is

the first step in this perspective. Establishing a GZMs and

soil profile of Peshawar urban settlement can be very useful

during preliminary planning, designing and feasibility

studies of various engineering projects in Peshawar. In

several countries of the world, proper guidelines are already

available to practicing engineers and forerunner geotechnical

engineers in the form of maps for geotechnical design

purposes [2]. This research is focused for general

establishment of geotechnical appraisal for construction

projects in Peshawar urban settlements. Geotechnical sub-

soil data currently available at Soil mechanics and Highway Engineering Laboratory, University of Engineering and

Technology Peshawar is utilized for preparation of these

maps.

2. OBJECTIVIES OF THE STUDY

The research study is designed to prepare sub-soil profile,

GZMs and to furnish sufficient necessary reliable data

regarding percentage of soil class distribution, classification

charactrestics, shear strength charactrestics and bearing

capacity of soils in the selected under study area of the

Peshawar urban settlements. This research work will assist

the geotechnical and civil engineers beforehand to plan the detail geotechnical investigation based on the provided sub-

soil profile and GZMs.

3. DESCRIPTION OF THE STUDY AREA

The study area consists of Peshawar urban settlements i.e.

Zone 5 and 6 having two hundred and eighty nine square

kilometers area located within Latitudes 33° 54′ to 34° 4′ N

and Longitudes 71° 23′ to 71° 43′ E (Fig. 1). The study area

ISSN 1013-5316; CODEN: SINTE 8 Sci.Int (Lahore), 25(4), 531-537, 2013 532

is characterized by broadly flat topography with gentle

undulations. The Peshawar valley is covered with

unconsolidated deposits of sand, silt and gravel [3].

4. METHODOLOGY During geotechnical zonation mapping exercise, the very

first step is the digitization of roads (metal and un-metal), rivers, urban settlements and boundary of the district

Peshawar which was carried out from the geo referenced

General Topographic Sheet (GTS) prepared by Survey of

Pakistan in 1986 using a scale of 1:5000. Digital Elevation

Model (DEM) of the Peshawar district at 10 m interval was

created from the National Aeronautics and Space

Administration, Shuttle Radar Topography Mission (SRTM)

90 m interval data for ascertaining the depth of the bore logs

from the Natural Surface Level (NSL). Positions of Standard

Penetration Test (SPT) soil samples were ascertained from

Global Positioning System (GPS) readings and assigned to the corresponding latitudes and longitudes. Using Inverse

Distance Weighted (IDW) interpolating technique, the soil

classes were coded as (1,3,6,2,7,8,9,10 and 11) owing to

facilitate the analysis of the soil class distribution, that were

found in the soil bore logs [4]. They are: Clayey sand (SC),

Clay (CL), Silty clay or Clayey silt (CL-ML), Poorly graded

gravel (GP), Clayey gravel (GC), Silt (ML), Silty gravel

(GM), Silty sand (SM), and Poorly graded sand (SP)

respectively. Soil class distribution was digitized after

interpolation and finally layouts of all layers of the study

area (Zone 5 & 6) were made. The GZMs were enlarged to a

scale of 1:70,000.Total one hundred and three SPT reports

were examined for the preparation of GZMs at depth 1 m

and 3 m, while soil profile strata chart was also prepared for the selected section. The database table used for the analysis

examination was constructed from: Borehole ID, Project

Name, Coordinates, SPT N-values, Soil class, Atterberg

Limits, Safe bearing capacity and Shear strength

characteristics.

5. RESULTS 5.1 Percentage of Soil Class Distribution in the Study

Area

At depth 1 m in Zone 5, clay and silty clay or clayey silt

(CL, CL-ML) cover 50 % area ,silt (ML) covers 1 % area,

clayey gravel and poorly graded gravel (GC, GP) cover 49

% area. clay and silty clay or clayey silt (CL, CL-ML) predominant at depth 3 m in geotechnical zonation map

which shows a higher percentage of 62.2 %, Poorly graded

sand (SP) shows 0.7 % area, Clayey gravel and poorly

graded gravel (GC, GP) cover 37.1 % area. Consequently, at

depth 1 m in Zone 6, clay and silty clay or clayey silt (CL,

CL-ML) cover 80 % area, clayey gravel and poorly graded

gravel (GC, GP) cover 20 % area. While at depth 3 m clay

and silty clay or clayey silt (CL, CL-ML) cover 87 % area,

clayey gravel and poorly graded gravel (GC, GP)

considerably reduced from 20 % area - at depth 1 m in Zone

6 to 13 % area (Fig. 2-5).

5.2 Classification Characteristics

The results of the SPT show that the liquid limits ranges

from 18.4 % to 33.1 %, plastic limit from 14.9 % to 21.1 %,

plasticity index 0.8 % to 13.2 % and the moisture content

ranges from 0.5 % to 34.8 % in Zone 5. While in Zone 6 the

liquid limits ranges from 18.1 % to 32.2 %, plastic limit

from 15.1 % to 21.2 %, plasticity index 0.6 % to 14.1 % and

the moisture content ranges from 1.5 % to 52.5 %.

Generally, Coarse - grained soils (gravels etc) are not very

sensitive to moisture change, whereas fine - grained soils

(clays etc) are sensitive to moisture changes. Cohesionless

soils have plasticity index, theoretically, is zero.

5.3 Shear Strength Characteristics

Direct shear test is employed for determining the shear

strength parameters, cohesion or inter-particle attraction (c)

and the angle of internal friction (ϕ). The results revealed

that the cohesion (c) in Zone 5 ranges from 454.1 to 1209.47

PCF while in Zone 6 ranges from 445 to 1427 PCF. The

internal friction angle (ϕ) in Zone 5 varies from 11.3° to

40.8° while in Zone 6 its varies from 22° to 33.7°. Owing to

the increasing amounts of the fines-sized particles, such as

clay, the cohesion of soil increases [5]. Shear strength

characteristics of the fine grained soils are influenced greatly by moisture content variations.

5.4 Bearing Capacity

The load – carrying capacity of the foundation soil and rock

Fig. 1: Land Cover Map of Peshawar District with

Study Area Zones.


without causing intolerable settlement of the structure is

called bearing capacity [6]. Tolerable settlement would not

affect the function or structural integrity of the structure and

is commonly set is about 1 inch. The highest value of the

safe bearing capacity was 2 TSF at depth 0.91 m (3 ft) and

width 3 ft in Hayatabad for an estimated settlement of 1 in recoded due to the poorly graded gravels and clayey gravels

(GP & GC) that reveals the increasing trend of angle of

internal friction resulting increase in bearing capacity of the

soil in Zone 5. In Zone 6 the minimum value of safe bearing

capacity at depth 0.91 m (3 ft) and width 3 ft for an

estimated settlement of 1 in was 0.2 TSF (Fig. 6-7).

5.5 Sub-Soil Profile Soil profile is a vertical cross section of the actual soil strata

at a given site showing sequence and thickness of soil layers

below the natural surface level [7]. The sub-soil profile

section AA covers the area from Hayatabad to Gulbahar in

Peshawar. The sub-soil profile clearly indicates the presence of surface stratum of gravels and silts in Zone 5 while in

Zone 6 the coarse grained soils i.e. gravels are overlaying

over clay (Fig. 8). Ground water table was not encountered

to the exploration depth of 7 m in the sub-soil profile map.

Fig. 2: Geotechnical Zonation Map (GZM) at Depth 1 m (Zone 5)



Fig . 5:

Geotechnical Zonation Map (GZM) at Depth 3 m (Zone 6)



Fig. 6: Bearing Capacity in TSF Zonation Map (Zone 5)

Fig. 7: Bearing Capacity in TSF Zonation Map (Zone 6)


Fig. 8: Sub-Soil Profile Map, Section AA (Zone 5 & 6)

6. DISCUSSION AND CONCLUSIONS It was observed during analysis that SPT N-values are

directly proportional to the soil strength and depth i.e. the

greater the N-values, the stronger the soil mass. The line

slope (m) shows upward trend which means that the ranges

from 0.9376 to 0.9796 for both zones i.e. 5 & 6. The

following range for the goodness of fit was considered, i. R2 > 0.95 means excellent correlation exists between

variables [8]. The Fig. 9 showing an excellent correlation

between the depth versus average SPT N- values of Zone 5.

ii. R2 = 0.90 to 0.95 means very good correlation exists

between variables [8]. The Fig. 10 showing a good

correlation between the depth versus average SPT N- values

of Zone 6.

Conclusion was made that the SPT N-values increase with

depth owing to pressure, compaction and increase in content

of clay and clayey silt or silty also the high value of friction

angle indicates dense conditions in the granular soils. The

relationships found up to 5 m depth are of straight line

equations with selected intercepting values 11.333 and

2.6458 are as shown in graph equations.

Fig. 9: Graph Showing Regression Analysis between depth

versus Avg. SPT N-value of Zone 5

Fig. 10: Graph Showing Regression Analysis between depth versus

Avg. SPT N-value of Zone 6


This research collates the available one hundred and three

geotechnical sub-soil SPT reports of Peshawar urban

settlements. The standard penetration N-values is an index

which is directly proportional to the soil strength. The work

will assist as a ready reference guide for practicing

geotechnical Engineers and Researchers in Peshawar. This is valuable in the aspect that, it will reduce considerably the

initial costs of new proposed projects which is to initiate in

areas covered in this paper.

7. REFERENCES

[1] Suwanwiwattana, P., Chantawarangul, K.,

Mairaing, W., & Apaphant, P., “The development of geotechnical database of Bangkok subsoil using

GRASS-GIS,” 2001, November, pp. 5-9.

[2] Hayat, K., 2003, “Geotechnical zonation and their

relation to geology of Pakistan”, Ph.D. Thesis,

University of the Punjab, Pakistan.

[3] Aslam, M., Hussain, A., Ashraf, M. & Afridi, A. G. K., 2006, Geological Map of North West

Frontier Province, Geological Survey of Pakistan.

[4] Aguib, A., 2005, “GIS application for constructing

knowledge base and representing 3d geotechnical

data”, Proceedings of 11th International Colloquium on Structural and Geotechnical

Engineering, Ain Shams University, Egypt.

[5] Jumikis, A. R., Soil Mechanics, Neeraj, Galgotia,

New Delhi, p. 33.

[6] Chandra, K. U., Soil mechanics and Foundation

Engineering, PHI learning private limited, New

Delhi, P. 138.

[7] Jumikis, A. R., Soil Mechanics, Neeraj, Galgotia,

New Delhi, p. 32.

[8] Hoffmann, J. P., Beacom, K. & Cooper, A.,

“Linear Regression Analysis : Assumptions and

Applications.”

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PROFILING AND ZONING OF GEOTECHNICAL SUB-SOIL DATA USING GEOGRAPHIC INFORMATION SYSTEM · 2016-01-25 · PROFILING AND ZONING OF GEOTECHNICAL SUB-SOIL DATA USING GEOGRAPHIC INFORMATION