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REVIEW OF CPT BASED DESIGN METHODS FOR ESTIMATING AXIALCAPACITY OF DRIVEN PILES IN SILICEOUS SAND

By

Juan Carlos Monz6n A.

B.S. Civil EngineeringUniversity of Florida, 2001

SUBMITTED TO THE DEPARTMENT OF CIVIL AND ENVIRONMENTAL ENGINEERINGIN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF

MASTER OF ENGINEERING IN CIVIL AND ENVIRONMENTAL ENGINEERING

AT THE

MASSACHUSETTS INSTITUTE OF TECHNOLOGY

JUNE 2006

02006 Juan Carlos Monz6n A. All rights reserved.

The author hereby grants to MIT permission to reproduceand to distribute publicly paper and electronic

copies of this thesis document in whole or in partin any medium now known or hereafter created.

Signature of Author:

Certified by:

Accepted by:

Departme of Civil and EnvironmentaThgjneeringMay 26, 2006

A-

A, ,,,,.Andrew J. Whittle

Professor of Civil and Environmental EngineeringI Thesis Supervisor

A

AndN4A-hittleChairman, Departmental Committee for Graduate Students

k4ASSACHUSETS INS EOF TECHNOLOGY

[JUN 7 2006

LIBRARIES

REVIEW OF CPT BASED DESIGN METHODS FOR ESTIMATING AXIALCAPACITY OF DRIVEN PILES IN SILICEOUS SAND

By

Juan Carlos Monz6n A.

Submitted to the Department of Civil And Environmental Engineeringon May 26h, 2006 in Partial Fulfillment of the Requirements for the Degree of

Master of Engineering

ABSTRACT

The Cone Penetration Test has been used for more than 30 years for soil exploration purposes. Itssimilarities in mode of installation with driven piles provides the potential of linking key variables of piledesign and performance, such as base resistance and shaft friction, to measured cone tip resistance.

Large scale pile load tests, performed in the last two decades, have shown better agreement with recentCPT based design criteria, than with conventional American Petroleum Institute (API) earth pressureapproach design guidelines. The CPT based design methods provide a more coherent framework forincorporating soil dilation, pile size effect, pile plugging during installation, and the friction at the pile-soilinterface.

A review, of four recent CPT based design methods and the API design guidelines, for estimating axialcapacity of driven piles in siliceous sands was performed by comparing their predictive performance to sixdocumented on-shore piles with load tests. First, a detailed site investigation based on CPT data wasperformed to validate the provided soil profile, and to evaluate the accuracy of the CPT readings toidentify and classify soil strata. Three piles were selected for further study and axial capacity calculations.

Three of the design methods, UWA-05, ICP-05 and NGI-05, prove to accurately predict axial pilecapacities for on-shore short piles founded on sites where sand dominates. Analysis against a larger andmore detailed database is required to validate their performance in multilayer soil profiles.

Thesis Supervisor: Andrew J. WhittleTitle: Professor of Civil and Environmental Engineering

2

ACKNOWLEDGMENTS

I acknowledge and gratefully thank, Mr. Thomas Shantz, Senior Research Engineer at the California

Department of Transportation (CALTRANS), who kindly provided the information that made the

execution of this thesis possible.

I would like to extend a special thank you to my thesis supervisor, Professor Andrew Whittle, for his

knowledge, critical thinking, enthusiastic interest, and for the time he dedicated to guide and teach me; not

only in this thesis but in my courses at MIT.

A warm thank you goes to my family, for their love, understanding, and support; to my mother for making

this Master possible; and to my grandfather, who introduced me to Civil Engineering, a passion we share.

Special thanks got to Diana Escobar, for her love, inspiration, encouragement, and for the life we are

about to start together.

This thesis is dedicated to the loving spirit of my sister Natalia, and her journey to recovery:

"Hoy no caminas junto a m', pero tus huellas me acompafian a tu encuentro."

3

TABLE OF CONTENTS

AB STRACT .............................................................................................................................................. 2

ACKNOW LEDGM ENTS ......................................................................................................................... 3

TABLE OF CONTENTS .......................................................................................................................... 4

LIST OF FIGURES ................................................................................................................................... 6

LIST OF TABLES ..................................................................................................................................... 7

1. INTRODUCTION ............................................................................................................................ 8

2. BACKGROUND ON DESIGN M ETHODS ................................................................................... 9

3. AXIAL PILE CAPACITY - OVERVIEW ..................................................................................... 11

3.1. Basic design forraulation ....................................................................................................... 11

4. DESCRIPTION OF DESIGN M ETHODS .................................................................................... 13

4.1. API-00 .................................................................................................................................... 14

4.2. FUGRO-05 ............................................................................................................................. 16

4.3. ICP-05 ..................................................................................................................................... 18

4.4. NGI-05 ................................................................................................................................... 22

4.5. LTW A-05 ................................................................................................................................. 24

5. CALTRAN S PILE DATA .............................................................................................................. 30

5.1. Pile-site characteristics report ................................................................................................ 31

5.2. CPT profiles ........................................................................................................................... 31

5.3. Load tests ............................................................................................................................... 31

5.4. Pile and site data overview .................................................................................................... 32

6. SOIL-PROFILE CHARACTERIZATION .................................................................................... 33

6.1. General procedure .................................................................................................................. 33

6.2. Site interpretation results ....................................................................................................... 38

7. AX IAL PILE CAPACITY PREDICTION ..................................................................................... 53

7.1. Spreadsheet input data ........................................................................................................... 53

7.2. General calculation procedure ............................................................................................... 53

7.3. Clay layers - Load contribution ............................................................................................. 54

7.4. Spreadsheet output ................................................................................................................. 55

7.5. Pile M IT-4 capacity prediction .............................................................................................. 55

7.6. Pile M IT- 1 capacity prediction .............................................................................................. 63

7.7. Pile M IT-5 capacity prediction .............................................................................................. 67

8. SUMMARY OF REVIEW OF CPT DESIGN METHODS...........................................................75

8.1. Tension loading......................................................................................................................75

8.2. Com pression loading ............................................................................................................. 76

8.3. API-00....................................................................................................................................77

8.4. FU GRO -05.............................................................................................................................77

8.5. ICP-05....................................................................................................................................78

8.6. N GI-05...................................................................................................................................78

8.7. U W A -05.................................................................................................................................79

9. CON CLU SION .............................................................................................................................. 80

REFEREN CES ........................................................................................................................................ 81

APPEN D ICES Appendix A - Site Investigation pile M IT-I .............................................................. 84

Appendix A - Site Investigation pile M IT-1 ....................................................................................... 85

Appendix B - Site Investigation pile M IT-5 .................................................................................. 91

Appendix C - Pile-soil profile for pile MIT-3.....................................................................................98

Appendix D - Pile-soil profile for pile M IT-6 ................................................................................ 99

Appendix E - MIT-1 - Axial capacity prediction - Second Scenario (Mostly sand profile)...........100

5

LIST OF FIGURES

Figure 3.1 - Three main phases during the history of a driven pile: ....................................................... 12

Figure 4.1 - Relative density classification (API 2000)......................................................................... 15

Figure 4.2 - FUGRO-05 dimensional parameters................................................................................... 17

Figure 4.3 - Interface friction angle, 5, variation with D50 (Lehane et al. 2005c).................................26

Figure 4.4 - Determination qc using the Dutch averaging technique (Lehane et al. 2005b).................28

Figure 5.1 - Caltrans Test sites (Olson and Shantz, 2004)..................................................................... 30

Figure 6.1 - Comparison of measured )' from frozen samples vs. qt (Mayne 2005)............................ 36

Figure 6.2 - Preconsolidation Stress in Clay from Net Tip Stress (Mayne 2005)................................. 37

Figure 6.3 - Pile MIT-4- Pile-soil elevations diagram........................................................................... 41

Figure 6.4 - Pile MIT-4 - Chart A - Vertical profile, CPT readings..................................................... 42

Figure 6.5 - Pile MIT-4 - Chart B - CPT normalized profiles................................................................. 43

Figure 6.6 - Pile MIT-4 - Chart C - Friction angle and relative density for cohesionless layers........... 44

Figure 6.7 - Pile MIT-4 - Chart D (Undrained strength and stress history of clay layers)..................... 45

Figure 6.8 - Pile MIT-4 - Chart E - Soil Classification (Robertson and Campanella, 1988)................. 46

Figure 6.9 - Pile MIT-1 - Pile-soil elevations diagram.......................................................................... 48

Figure 6.10 - Pile MIT-5 - Pile-soil elevations diagram........................................................................ 51

Figure 7.1 - MIT 4 - Tension load test and predicted axial capacity......................................................57

Figure 7.2 - MIT-4 - Tension - Axial capacity distribution................................................................... 59

Figure 7.3 - MIT 4 - Compression load test and predicted axial capacity............................................. 60

Figure 7.4 - MIT-4 - Compression - Axial capacity distribution.......................................................... 62

Figure 7.5 - MIT-1 - Tension load test and predicted axial capacity ................................................... 64

Figure 7.6 - MIT-I - Tension - Axial capacity distribution...................................................................66

Figure 7.7 - MIT-5 - Tension load test and predicted axial capacity ................................................... 69

Figure 7.8 - MIT-5 - Tension - Axial capacity distribution...................................................................71

Figure 7.9 - MIT-5 - Compression load test and predicted axial capacity ............................................ 73

Figure 7.10 - MIT-5 - Compression - Axial capacity distribution........................................................ 74

6

LIST OF TABLES

Table 4-1 - Timeline of the development of design methods for offshore piles (Chow 2005)................13

Table 4-2 - Coefficients of lateral earth pressure, Kf..............................................................................14

Table 4-3 - API RP 2A (2000) design parameters for Cohesionless Siliceous Soil .............................. 15

Table 5-1 - Available information matrix .............................................................................................. 30

T able 5-2 - C PT soundings ......................................................................................................................... 32

T able 5-3 - Site inform ation ........................................................................................................................ 32

T able 5-4 - Pile properties........................................................................................................................... 32

Table 5-5 - Load-deflection tests ................................................................................................................ 32

Table 7-1 - MIT-4 - Coverage of pile embedment per layer ................................................................. 55

Table 7-2 - Pile MIT-4 - Pile axial capacity overview ............................................................................ 56

Table 7-3 - Pile MIT-1 - Pile axial capacity overview based on profile derived in Section 6.2.2...... 63

Table 7-4 - MIT-5 - Coverage of pile embedment per layer................................................................. 67

Table 7-5 - Pile MIT-5 - Pile axial capacity overview ............................................................................ 67

Table 8-1 - Summary of prediction of total pile capacity in Tension ..................................................... 75

Table 8-2 - Summary of prediction of total pile capacity in Compression............................................ 76

7

1. INTRODUCTION

Historically, pile design in sands has been based on an earth pressure approach, and described by simple

linear relationships for the unit shaft friction and unit base resistance. In both cases, the approach imposes

limiting values at some 'critical depth' expressed either in absolute terms or normalized by the pile

diameter (Randolph 2003). This approach has been incorporated into the American Petroleum Institute

(API) offshore pile designs guidelines since 1969.

The Cone Penetration Test (CPT), and piezocone penetration test (PCPT), have been widely used in

geotechnical site investigations for more than 30 years. In these tests, soil profiling is based on continuous

measurements of cone resistance (q), sleeve friction (f,) and pore pressures generated at the tip or base (u,

or u2 respectively) of the cone as it penetrates the soil at a constant rate. These tests trace its origins to the

work of Wissa and Torstensson in 1975 (Baligh et al. 1980).

The similarities in mode of installation of driven piles and CPT probes indicated that further development

of the CPT method should improve the pile design methods. Early attempts at correlating CPT

measurements to pile capacities was performed by Bustamante and Gianeselli (1982), and has evolved to

link cone tip resistance (qg) to pile's base resistance and shaft friction resistance.

Large scale pile load tests performed in last two decades have advanced the understanding of driven piles

in sand, as they have identified the gradual degradation of shaft friction at any given depth as the pile is

driven progressively deeper (Randolph 2003). The results of the load test differ significantly from

predictions based on conventional API design criteria but show good agreement with those based on more

recent CPT based design criteria.

The present document provides a comparative review of five design methods for estimating axial capacity

of piles in siliceous sands. The design methods comprise four recent (2005) CPT based design methods,

and the API earth pressure approach.

The current review compares the predictive performance of the proposed CPT design methods using data

for six well documented on-shore piles and load tests. Chapters 2 to 4 present an overview of methods

used to estimate axial pile capacity in sands and the four proposed CPT design methods. Chapters 5 and 6

describe the site conditions and soil profile interpretation based on CPT data. Chapters 7 and 8 apply and

compare the proposed CPT design methods to estimate the capacity measured in the pile load tests.

8

2. BACKGROUND ON DESIGN METHODS

In the last two decades, a series of load tests were performed on driven piles at sufficiently large scale to

obtain reliable pile load test data in very dense sand for development of improved offshore pile design

criteria for North Sea type conditions and to contribute to the definition of new Eurocodes. These load

tests were part of a European initiative called EURIPIDES, designed to provide more confidence and less

conservatism for new design guidelines for offshore pile foundations (Zuidberg & Vergobi, 1996).

The Euripides program comprised of a highly instrumented (0.76 m) diameter driven pile that was tested

at one location, extracted and redriven and tested at a second location. Static compression and tension tests

(30 MN) were performed at three penetration depths (30.5 m, 38.7 m and 47.0 m) at the first location, and

at one penetration depth (46.7 m) at the second location. The latter series of tests was repeated after 1.5

years. Further background to the Euripides tests can be found in Zuidberg & Vergobi (1996).

The results of the EURIPIDES load tests revealed that the American Petroleum Institute (API) offshore

pile designs guidelines were very conservative and underestimated the pile load capacities in dense sands.

These findings confirmed earlier results obtained from load tests performed by Saudi Aramco in Ras

Tanajib in the Arabian Gulf in 1985 (Helfrich et al., 1985; Stevens and Al-Shafei, 1996). In this program a

highly instrumented pile was driven to 17 m depth and tested. After pulling the pile, a casing was driven to

17 m below ground level, the soil plug removed and the instrumented test pile was driven through this

casing to 25 m depth. Subsequently, another series of static compression and tension tests was performed.

The tests results differed significantly from predictions based on conventional offshore design criteria

given in API RP2A. However, good agreement was obtained with predictions made with more recent,

CPT-based design criteria (Helfrich et al. 1985).

In 2001, the results of EURIPIDES became public, and together with the progress in Cone Penetration

Tests (CPT) site investigations methods, led to the development and/or confirmation of recently proposed

design methods that improved the predictions of the API recommendations, particularly for dense

siliceous sands. These methods were ICP and NEW FUGRO.

Between 2002 and 2004, API funded a project and appointed Fugro N.V. to compile pile load tests results

into a large database, with the objective of comparing and revising those results against the API guidelines

for design of offshore piles; the NEW FUGRO method; and the ICP method that had been successfully

applied in foundation designs of 14 North Sea platforms since 1996.

9

At the end of 2004, the API project was completed; it concluded that the API design guidelines were very

unreliable; it provides less conservatism for increasing length/diameter ratio, and more conservatism with

increasing relative density. For the ICP method it concluded that it was reasonably reliable, in particular

for compression capacity; slightly unconservative for piles in tension; and conservative for end bearing.

In early 2005, the API piling sub-committee, requested Prof. Lehane from the University of Western

Australia (UWA), to conduct an independent evaluation of the existing API recommendations (API-00)

for offshore structures, and those given by the recently proposed design methods for estimating axial

capacity in driven piles, namely: Imperial College (ICP-05), Fugro (FUGRO-05), and the Norwegian

Geotechnical Institute (NGI-05) for axially loaded piles in sand. This review, which was conducted by

Lehane et al. (2005a,b,c), included the compilation of a significantly larger database of pile load tests than

employed in the development of the 3 'new' CPT based design methods and highlighted limitations of

these methods.

The review of the 3 CPT design methods by Lehane et al (2005a,b,c) led to development of the UWA-05

method, and the publication of a comprehensive study that evaluates the performance of the design

methods against a large load pile test database that combines the API and UWA information (Lehane et al.

2005a).

10

3. AXIAL PILE CAPACITY - OVERVIEW

3.1. Basic design formulation

The ultimate capacity of a pile, defined as Qui, is the load that will cause a pile to fail. The value of Qut

(Equation 3-1) is the sum of the contribution of the ultimate shaft resistance Qsf, and the ultimate end

bearing resistance Qbf, minus the weight of the pile.

Quit = Qsf + Qbf -Weight (3-1)

The ultimate shaft resistance of a pile, Qsf, is the sum of the unit shaft friction applied along the embedded

surface of the pile (Equation 3-2).

Qf = 7D r dz (3-2)

The unit shaft friction is defined as the product of the horizontal effective stresses at the failure condition

and the mobilized friction coefficient along the pile's length (Equation 3-3). The mobilized friction

coefficient is defined as the tangent of the pile-soil friction angle, (6):

T f = a-' h . tan 5 ( 3-3 )

The ultimate end bearing resistance, Qbf, is the maximum load that a pile can mobilize at its tip. It is

calculated as the product of the ultimate unit end bearing stress, qbf, and the pile's base area, Ab. The

ultimate unit end bearing stress will be reached at large displacements, therefore the practical definition of

ultimate is often taken as the unit end bearing capacity at a displacement of 10% the pile diameter, qbo.I.

This definition is summarized in Equation 3-4.

g * (34)

Qbf 2

The pile's base area, Ab, corresponds, for the case of closed-ended piles, to the actual physical area of the

pile. In the case of open-ended piles, the formation of a plug must be evaluated, as to determine if the unit

end bearing stress acts solely on the annulus of the pile, or on the soil plug formed in the interior of the

pile during driving. The failure mechanism of the plug can occur either through shear failure of the soil

against the pile's internal surface, or as a bearing failure of the plug's tip. Recommendations to assess the

formation of the plug in an open-ended pile are provided in Lehane et al. (2002) and Paik et al. (2001).

11

The general form of Equation (3-1) for an open-ended pile can be re-written as:

Quit = Qsf+Qbf - Weight =(AD - Jv dz)+ /,Z J qboA -Weight (3-5)

From the previous equations it can be noted that the difficulty in calculating the ultimate pile capacity

depends on the estimation of the stress parameters qbf (or qzo.1) and -ref (or c-'h). This estimation is

challenging because it is influenced on several factors that inherently affect the initial state of stresses in

the soil and that are difficult to quantify. These factors include, but are not limited to: the direction of

loading, soil disturbance due to type of pile installation, pile's properties, size effects, set-up time, etc.

Figure 3.1 provides schematic drawings, of the main phases in the lifetime of a pile, that illustrate some of

the mentioned factors for the case of driven piles.

(a) (b) (c)

Figure 3.1 - Three main phases during the history of a driven pile:

(a) installation; (b) equilibration; (c) loading (Randolph, 2003)

12

4. DESCRIPTION OF DESIGN METHODS

The present section will introduce the formulations and describe the characteristics of the five design

methods, for estimating axial capacity in driven piles in siliceous sands, being reviewed in this document.

(Lehane et al. 2005a)

The design methods can be classified in two groups:

i) Existing API recommendations for offshore structures(API-00), which are based on an earth

pressure approach.

ii) Recent CPT based design methods, namely:

" Fugro, named hereafter (FUGRO-05)

" Imperial College, named hereafter (ICP-05)

* Norwegian Geotechnical Institute, named hereafter (NGI-05)

0 University of Western Australia, named hereafter (UWA-05)

The following figure presents a timeline of the history and development of the design methods.

Method Dates Notes

API 1969 -2005 Earth pressure approach

ICP 1996 -2005 Class-A prediction for EURIPIDES

NGI 1999 -2005 Developed using the NGI database and EURIPIDES

FUGRO 2001 - 2005 Developed using EURIPIDES and the Fugro databaseof open-ended piles using the ICP expression as abase

UWA 2005 Developed using an expanded database

Introduces the use of the IFR to calculate area ratiofor shaft capacity of open ended piles based on cavityexpansion models.

Uses FFR for base capacity of open-ended piles.

Table 4-1 - Timeline of the development of design methods for offshore piles (Chow 2005)

13

4.1. API-00

The design method identified as API-00, corresponds to the recommendations included in the American

Institute of Petroleum manual for offshore pile design, namely: API 2000.

4.1.1. Shaft resistance

The total shaft resistance of the pile is defined by the integral of the unit shaft friction along the pile shaft,

as indicated in equation (3-3). The unit shaft friction is expressed using a Coulomb friction approach that

in general relates the frictional force between two surfaces to the perpendicular normal force applied and

modifies it by a friction coefficient. The friction factor corresponds to the roughness of the contact

materials. Following this approach, the unit shaft friction (tr) is defined as the local effective horizontal

stress on the pile - expressed in terms of the corresponding effective vertical stress (c' 0o) multiplied by a

coefficient of lateral earth pressure (Kf) - and modified by the friction coefficient that corresponds to the

tangent of the friction angle (6) between the soil and pile wall. The previous definition is summarized in

equation (4-1), where the coefficient of lateral earth pressure and the friction coefficient are grouped into a

term named as beta (P).

'f = Kf ' tan 5 -- 'v0 = ).al V- - f (4-1)

It can be noted in equation (4-1), that the value of the unit shaft friction (trf) increases proportionally to the

vertical stress(a',0 ), nevertheless the API-00 design method limits the unit shaft friction (Tflim) to the

values indicated in Table 4.3.

Open ended or Closed end or

unplugged piles plugged piles

Compression 0.8 1.0

Tension 0.8 1.0

Table 4-2 - Coefficients of lateral earth pressure, Kf

The friction angle (6) between the soil and the pile is specified for different densities of non-cohesive

materials in Table 4.3. Classification of a material under a given density can be performed from the angle

of internal friction or the relative density of the material, as indicated in Figure 4.1, which is included into

the API (2000) guidelines.

14

#120 Q*

300

250

200

-150

100

50

00

Figure 4.1 -

*, angle of internal friction0* 3 4 0 45*

20 40 so 80v 1WRELATIVE DENSITY, %

Relative density classification (API 2000)

Soil-Pile Limiting Skin Limiting Unit EndFriction

Density Soil angle, 6 Friction, tflim Nq Bearing, qbo.iI1m

Description [degrees] [kips/ft2 ] [kPa] [kips/ft2 ] [kPa]

Very loose Sand 15 1 47.8 8 40 1.9

Loose Sand-silt

Medium Silt

Loose Sand 20 1.4 67 12 60 2.9

Medium Sand-silt

Dense Silt

Medium Sand 25 1.7 81.3 20 100 4.8

Dense Sand-silt

Dense Sand 30 2 95.7 40 200 9.6

Very Dense Sand-silt

Dense Gravel 35 2.4 114.8 50 250 12

Very Dense Sand

Table 4-3 - API RP 2A (2000) design parameters for Cohesionless Siliceous Soil

15

Vly LOOsM Mwwln Dense VeryLoose Dann Dens

"h waerlTabls

Sand Belowthe w*WeTable

4.1.2. Open ended vs. closed end piles

The calculations of the axial capacity of a driven pile must consider the condition of the pile at its tip. For

the case of a closed-end pile it is clear that the end bearing area corresponds to the physical area of the

pile, in this case no internal shaft friction is possible.

In the case of an open ended driven pile, the condition at the tip must be evaluated for two scenarios:

" The pile is plugged at its tip. For this case the contribution of the plug must be evaluated by

comparing the end bearing capacity of the plugged end area and the shaft friction of the column of

soil against the inner area of the pile. The smallest value will control.

" The pile is unplugged at the tip, in this case the end bearing area corresponds to the physical

annular end area of the pile.

4.1.3. End bearing capacity

The tip resistance of a pile is calculated from the unit end bearing capacity of the soil times the end

bearing area of the pile in contact with the soil.

The unit end bearing capacity is calculated by modifying the effective vertical stress by a dimensionless

bearing capacity factor Nq, (included in Table 4.3) as expressed in equation (4-2). Recall that the unit end

bearing capacity for the API-00 method is defined as the base resistance for a pile tip displacement

equivalent to 10% of the outer diameter of the pile.

qbo.1 = Nq -a ' 0 < qbO.1 11 (4-2)

The maximum limiting values of unit end bearing capacity (qo.iiim) for different densities are tabulated in

Table 4.3; Nq values are also included.

4.2. FUGRO-05

The Fugro-05 design method was developed by Fugro Engineers B.V. for the Fugro Group, an

engineering support company that specializes in geotechnical, survey, and geoscience services

(www.fugro.com).

16


For compression loading the unit shaft friction is defined as:

0.05 -0.9

Zf =O.O8.q C Pa )" RP a R *

0.05 I

rf =0.08 -q a O* (4).0.9 hC Pa )4R*)

For tension loading the unit shaft friction is defined as:

. =0.15 -M -0.85

r,=0.045.q -' max ,4hPa L C

where:

q, = cone tip resistance

C-'vo = vertical effective stress at depth z

h = distance measured from the pile tip,

h = pile length - depth z

R = outside radius of pile (D/2)

Ri= inside radius of pile (Di/2)

R* = equivalent radius = (R2 -R12)0.

R* = R for closed end piles

for h/R* > 4

for h/R* < 4

Pilelength

Figure 4.2 - FUGRO-05 dimensional parameters


The unit end bearing is related to the average cone tip resistance (q, ) and area ratio (Ar). The cone

resistance at the tip should be averaged over a distance ± 1.5 pile diameters from the pile tip following

the recommendations presented by Bustamante & Gianeselli (1982)

-- >0.5

qO 1-= 8.5. - -C- A,Pa Pa)

q = cone tip resistance averaged over a distance ± 1.5 D from the pile tip

Ar = area ratio = 1 -(Di/D) 2 ; Di = 0 for closed end piles

where:

(4-6)

17

(4-3)

(4-4)

(4-5)

z

2R=D4--.b

4.3. ICP-05

The ICP design method was developed from field measurements with the Imperial College Pile at the

University of the same name in London, UK. The shaft capacity equations were based on measurements

made using a closed-ended instrumented pile and soil mechanics principles. The equations were later

revised to include hypotheses made for open-ended piles and confirmed in full scale load tests. The ICP

method has been used in the industry since 1996 and has been validated on a database of 65 pile tests

(Chow 2005).


The method provides distinct approaches for calculating the unit shaft resistance based on the axial

loading condition of the pile.

Pile under COMPRESSION loading

if = 0-',f -tan , = (-'r, +A -'rd tan t5, (4-7)

where

5= constant volume interface friction angle

O'rf = radial effective stress at failure = (O-'rc +A -'rd

C're= radial effective stress after installation and equalization

A U',d = change in radial stress next to the shaft during axial loading of the pile

The value of the constant volume interface friction angle should be measured directly in laboratory

interface shear tests, but may be estimated as a function of mean effective particle diameter (D 50) (Figure

4.3.)

The radial effective stress after installation and equalization (a're ) is defined for this method as follows:

at', =0.029 - a 0 . max ,8 (4-8)Pa R3

where:

ge = cone tip resistance from CPT

('), = vertical effective stress at depth z

h = distance measured from the pile tip; h = pile length - depth z

18

R = outside radius of pile

Ri= inside radius of pile

R* = equivalent radius = (R2 -Ri2)O-; R* = R for closed end piles

For the case of piles with a non-circular cross section (closed-end), the value of R* corresponds to the

radius of a circle with equivalent base area to that of the non-circular pile:

R*= (4-9)

where:

A = gross sectional area of pile (non-circular)

This assumption is only valid for unit shaft friction, i.e. perimeter calculations, and should be modifiedfor unit end bearing capacity area calculations, please refer to corresponding sections!

The change in radial stress (A a',d) is related to dilation at the pile interface during loading. This dilation

(lateral expansion) can be calculated using a cylindrical cavity expansion analogy.

ArACT', = 2 G - (4-10)

R

where

A r = interface dilation, it is estimated at approximately 0.02mm for a lightly rusted steel pile.

G = shear modulus of the soil

R = outside radius

Lehane et al. (2005a) suggest to determine the shear modulus from the small strain shear modulus

(i.e. G = GO), and indicate that this can be estimated as a function of the cone tip resistance from Baldi et

al. (1989):

Go = q .0203 +0.001257 -1.2lx0-5q and )r= q/('vo pa) 0 5 (4-11)

It was found during the calculation phases of this study that Equation (4-11) produced "jumps" for certain

values of cone resistance (qc) which corresponded to a ratio of log(q/a'vo) = 2.11. This unusual behavior

was verified by comparing Equation (4-11) with the data provided in the original paper by Baldi et al.

(1989). It was calculated that the equation that best fitted the data presented in a figure in that paper

(Figure 5 - Q, vs. Go correlation for uncemented predominantly quartz sands) is of the form:

19

-0.7503

Go = q, .1504.1. c (4-12)

In this study, Equation (4-12) was used in substitution of Equation (4-11) for calculating the small strain

modulus.

Pile under TENSION loading

Vf = a .(0.8 - a',+A a',d) tan 5, (4-13)

where

a = 1.0 for closed-end piles and 0.9 for open end piles

Refer to previous section for description of other factors in equation (4-13).


Closed-end piles

The unit end bearing is considered in this method as a function of the average cone tip resistance (qc)

and pile-cone diameter ratio (D/DcpT). The cone resistance at the tip should be averaged over a distance

± 1.5 pile diameters from the pile tip following the recommendations presented by Bustamante et al.

(1982).

The formula for the normalized unit end bearing follows:

qbo. /(qc)= max I - 0.5 log( DU , 0.3 ( 4-14 )

where:

q = cone tip resistance averaged over a distance ±1.5 D from the pile tip

Dcr = 0.036 m

20

Equation (4-14) sets a lower bound to the ratio q* I I / ) at a value of 0.3, one can calculate by setting

1-0.5log D ) = 0.3, that the maximum pile diameter that satisfies this equation is D = 0.9 m, meaning(DCPr

that the development of the method, and hence its applicability, is limited up to this value.

For the case of piles with a non-circular cross section (closed-end), the method considers that the value of

the unit end bearing (qo.1) does not vary due to area size or shape effects at the pile tip (i.e. area ratio, Ar),

therefore the method recommends to calculate the unit end bearing, as follows:

qbO. /(q 0.7 (4-15)

Open-ended piles

The method defines two possible states of an open-end pile, completely plugged or unplugged. The

criteria to determine if a pile should be considered as plugged is indicated in the next equations:

Di < 0.2 (Dr-30) (4-16)

Di< 0.083- -- ( 4-17 )DCPT Pa

where:

Di= inside diameter of the pile in meters

Dr = relative density expressed in percentage

* Plugged piles

Given that a plugged condition in the pile tip is estimated by the previous method, the unit end bearing

capacity (qo.1) can be calculated with the following equation:

qbo./(qc)= max 0.5 - 0.2 5 log(D ,0.15, Ar (4-18)

where:

Ar = area ratio = 1 -(Di/D) 2

Equation (4-18) sets a lower bound to the ratio qbO. I / ) at a value of 0.15, one can calculate that the

maximum pile diameter that satisfies this equation is D = 0.9 m, equal to the limit set forth by the method

for closed-end piles.

21

* Unplugged piles

In the case of an unplugged open-end pile, this design methods assumes that the unit end bearing is

provided by the annular pile area alone (no contribution of the inside shaft resistance) and it is a function

of the average cone tip resistance and the area ratio of the pile (a size effect factor):

qbO.I/(q) A, (4-19)

Note by comparing equations (4-18) for the condition of qbo. = 0.15 and equation (4-19) that it is

possible for an unplugged pile to have higher unit end area capacity than a plugged pile.

4.4. NGI-05

The Norwegian Geotechnical Institute (NGI) design method was established from a data base from high

quality pile tests in sand. (Clausen et al. 2005). The method determines the unit shaft resistance in tension

at a point along the pile's shaft as a function of the relative density of the material, the state of effective

vertical stress, the location of the point in relation to the total depth of the pile, and the condition of the

pile tip: rskin tension = f (Dr, a-'yo , z/zti, , open/closed tip)

The method assumes that the unit shaft resistance of the pile in compression is related to the tension case

by a correlation factor of 1.3: Tfcompression= 1.3 x tf tension

The unit end bearing capacity is defined for the NGI design method as a function of the cone resistance,

the relative density, and the condition of the pile tip: qtip = f (q; , Dr, open/closed tip)


The unit shaft resistance along the pile is given as:

=Dr - Fd -Fj, - F., - F (4-20)Ztip

The unit shaft resistance is set to have a lower limiting value given for each point along the pile as:

Tf (z)> 0.1- ', (4-21)

where:

zei,= pile tip depth

22

pa = atmospheric pressure, expressed in units corresponding to the desired unit shaft resistance

FD. = 2.1(Dr-0.1) 1 7 , with Dr expressed in fractions.

Fload = 1.0 for tension and 1.3 for compression

F = 1.0 for driven open ended piles, and 1.6 for closed-end piles

Fmat = 1.0 for steel and 1.2 for concrete

Fsig (a'vW/pa)~ 2 5 calculated at the depth (z) of the point of interest.

The method introduces a ratio of z/zti,. This value relates the depth of any point along the pile shaft to the

depth of the pile tip. The values of depth should be measured from the top soil elevation, not the pile

head. This ratio includes an effect of reduction of the side friction with depth. This effect is related to the

friction fatigue of the material around the pile. As the pile is driven deeper into the soil, the upper layers

of soil will experience more disturbance from the passing pile than the lower layers.

The NGI method calculates the relative density (Dr) from the cone resistance, (qe):

Dr =0.4- ln c 1 (4-22)22(o', pa )O.P _

The previous equation can provide values of Dr > 1, these values should be used. NGI also developed a

best fit relationship to correlate standard penetration test values (NI) to cone resistance equivalence. The

correlation is as follows:

qc =2.8 -N, -Pa (4-23)

The measured N1 values correspond to blow counts corrected for a reference confining pressure of 1 atm,

as introduced by Peck et al. (1974):

N =CN -N (4-24)

where: CN = 0.77log 20( 'Y V (TSF)

N = Standard penetration resistance measured in the field (Blows/ft)


The unit end bearing capacity is defined for the NGI design method as a function of the cone resistance at

the pile tip level (q,up), the relative density (Dr), and the condition of the pile tip: open or closed end.

23

For the case of a driven closed-end pile the unit end bearing capacity is expressed as:

q =- 0.8 ''' (4-25)1+ Dr

For the case of a driven open-end pile the unit end bearing capacity is calculated from the smallest value

of the core resistance (internal side friction of the plug-pile and base resistance of the annulus of the pile),

and the base resistance of a plugged condition.

The core resistance is calculated assuming that the state of stress of the soil against the pile annulus

corresponds to cone resistance, qg, and that the value of internal side friction of the plug-pile interface is

equal to 3 times the external value of the unit shaft resistance.

The end base resistance of the plugged portion of the pile is expressed as:

qbo.1 = '0.7 (4-26)l+3D,.

4.5. UWA-05

The UWA-05 method was developed at the University of Western Australia, at Perth, Lehane et al.

(2005b). It was proposed based on the findings of a review process of the previously described CPT based

design methods, performed at UWA at request of the API sub-committee on piling (Lehane et al., 2005a)

and against a wider load test database that comprised 231 tests.


The method provides the same approach for calculating the unit shaft resistance for compression and

tension loading, the only difference being the reduction of the shaft resistance by 25% for the case of the

tension loading.

Vf = af' 'd ta = ', (4-27)

where

'rf = local shear stress at failure along the pile shaft

5, = constant volume interface friction angle

24

O'fr = radial effective stress at failure = (a'rc +A -'rd )

a'c= radial effective stress after installation and equalization

A u'rj = change in radial stress due to loading stress path

f/fe = 1 for compression loading and 0.75 for tension loading

The value of the constant volume interface friction angle (8cv) is related to the relative roughness of the

steel and the soil (Uesugi et al. 1986) and it should be measured directly in laboratory interface shear

tests, but it may be estimated as a function of mean effective particle diameter (D50) indicated in

Figure 4.3.

The radial effective stress after installation and equalization is defined for this method as follows:

a' =0.03 -q - Ar,f 0 .3 max C,2 ]-0-5 (4-28)

where:

qc = cone tip resistance from CPT

Areff = effective area ratio = 1 - IFR(Di/D)2

IFR = Incremental Filling Ratio

Di= inside pile diameter. (Di = 0 for closed ended piles)

D = outside pile diameter

h = distance measured from the pile tip; h = pile length - depth z

A simplified approximation for IFR averaged for the last 20 pile's diameters of penetration is considered

to be a function of the pile inside diameter (Di) is given as:

IFRavg = min 1L1,JJ Dj: expressed in meters (4-29)

The change in radial stress is assumed for this method to be minimal for full scale offshore piles, it can be

expressed using a cylindrical cavity expansion analogy:

Ar

A-'rd = 4G-- (4-30)D

where

A r = interface dilation, it is estimated at approximately 0.02mm for a lightly rusted steel pile.

25

G = operational shear modulus of the soil ( G = G. is assumed). The method suggests to

determine the shear modulus from an equation based on Baldi et al. (1989):

G=q, .185*q 1Nj0. (4-31)

qclN = (q a a )05 (432)

For the case of piles with a non-circular cross section (closed-end), the value of R* corresponds to the

radius of a circle with equivalent base area to that of the non-circular pile.

32 -Employed fordatabaseovaluation

I Li I 11

30 T I i i I FI I

26- 24e-1 -r4-4 e4c-4 t+o+ I- - I- I 1-4

I I I1II 1I liii

22 - - 1T-T11 F1 - 1 TT17F117 FT -r-

26 ILJ~44L I..4 LLt[I42

I III'III I

l | | III! i i| I i I i i i I Il

I l i i l i I 11111||

20

0.01 0.1 1 10

Median Grain Size, D5o (mm)

Figure 4.3 - Interface friction angle, 8, variation with D50 (Lehane et al. 2005c)

The UWA-05 and ICP-05 share the same basic formulation for calculating unit shaft frictions (e.g.

equation 4.27 and 4.8 respectively), but differ in the estimation of the degree of soil displacement caused

by pile installation. In the UWA-05 method, the final degree of displacement is expressed in terms of an

effective area ratio, A,,eff, (Equation 4-28). This ratio accounts for the degree of displacement that is

imparted to any given soil strata during pile installation, i.e. the displacement experienced by that strata

when it was located in the vicinity of the tip during driving. The effective area ratio is unity for closed-

ended piles; for open-ended piles, this ratio accounts for the soil displacement due to the pile material

itself and the additional displacement imparted when the pile is partially plugging or fully plugged

during installation (Lehane et al. 2005c).

26


In this design method the unit end bearing is determined in a general case for open and closed ended piles

without the explicit consideration by the user of a plug formation at the pile's tip. In this regard the

method is user independent. The unit end bearing capacity for a displacement, 6 = 0.1 D, at the head of

the pile is given by:

qbO. = 0.15 +0.45 -A,,, (4-33)

where

q = cone tip resistance averaged using the Dutch method. See Figure 4.4.

In the Dutch method, the pile outside diameter (D) should be used for closed-end piles, while an effective

diameter must be used for open-end piles.

The effective diameter should be calculated using this equation:

D= D (Arb,eff (4-34)

where:

Arb,ff= effective area ratio, which is unity for a closed-ended or fully plugged pile.

Arbeff =1 - FFR -(D /D) 2 (4-35)

FFR = Final Filling Ratio, measured at the end of pile driving, and averaged over a distance of 3

diameters from the pile tip.

An approximate formula for estimating FFR as a function of the pile internal diameter (Di), is given by:

0.2~FFR =min 1, 1. Di: expressed in meters (4-36)

Lehane & Randolph (2002), have shown that, if the length of the soil plug is greater than 5 internal pile

diameters (5Di), the plug will not fail under static loading, regardless of the pile diameter.

27

Cone resistance qc

e

?48D

Envelope of c ,aminimum q, values I

b

2

F

Procedure:

1 = Average q. over adistance of yD below the piletip (path a-b-c). Sum q,values in both the downward(path a-b) and upward(path b-c) directions. Useactual q values along path a-band the minimum path rulealong path b-c. Compute q.,for y values from 0.7 and 4.0and use the minimum q.values obtained.

qc2 = Average q. over adistance of SD above the piletip (path c-e). Usethe minimum path rule asfor path b-c in the q%computations. Ignoreany minor 'x' peakdepressions if in sand,but include inminimum path if in clay.

Figure 4.4 - Determination q, using the Dutch averaging technique (Lehane et al. 2005b)

The authors of the UWA design method indicate that the Dutch averaging procedure provides similar

results (q, ) as the procedure of averaging the cone tip resistance over a distance ± 1.5 pile diameters

from the pile tip recommended by Bustamante et al. (1982), given that the values of qc do not vary

significantly at the pile tip.

For offshore conditions the CPT profiles are often not continuous, and therefore the UWA authors present

a conservative approach for averaging q, , Figure 4.4:

(4-37)

where:

qca = is the minimum value of qc over the depth interval extending from the pile tip to a depth of

between 0.7 D* to 4 D* (D* as in equation 4-34)

qcb = is the average qc value from the tip of the pile to a height of 8 D* above it.

28

0

i-

6

qC = (qca, -- cby )2

4.5.3. Simplified UWA-05 desian method

The UWA methods presents a simplified version of the method applicable to offshore piles with diameter

equal or larger to 1.00 m. For this dimension the incremental filling ratio (IFR) is equal to unity, and the

stress loading path tends to zero (A cr'rd ~ 0), and equation (4-27) takes the form of equation (4-38) in

compression and equation (4-39) in tension.

4.5.4. Shaft friction in compression

0.3 F (h~ \-0.5 (-8=0.03 -q, - A,m.3 Max ,2 ( 4

L D JJ] 4-8

4.5.5. Shaft friction in tension

=0.75-0.03 -q [ - ,.3 max ,52)] (4-39)

where:

q,= cone tip resistance from CPT

Ar = area ratio = 1 - (Di/D) 2

D = outside pile diameter

h = distance measured from the pile tip; h= pile length - depth z

4.5.6. End bearing

qbo.1 /(qc = 0.15 +0.45 -Ar (4-40)

where

Ar = area ratio = 1 -(Di/D) 2

Di= 0 for closed-end piles.

29

5. CALTRANS PILE DATA

The California Department of Transportation (Caltrans) gathered information from hundreds of pile load

tests performed since the 1960's on driven piles, and adjusted it to create a data set of 319 tests performed

on 227 piles at 75 bridge sites (Olson and Shantz, 2004). Most of the tests were performed in heavily

populated areas along the California coast (Figure 5.1).

Eureka

San 0 PC entoRosa ac

Bay 0 ModeArea oSalins

*P Visalia

a n 0

Figure 5.1 - Caltrans Test sites (Olson and Shantz, 2004)

Mr. Thomas Shantz, Senior Research Engineer at Caltrans, kindly provided data from 6 project sites in

Los Angeles and San Francisco for this research project.

The information provided included site characteristic reports, CPT soundings, and pile load-deflection test

results. The following table provides a summary of the available information for each of the six sites,

arranged under an arbitrary numbering system (MIT #) that will be used in this document to reference the

pile information in a brief manner.

MITID ride lcatonCPT Site report &MIT ID Bridge location Sounding Load Test

1 North East Conn. OC, Br. No. 57-783F UTC-40 38-012 Los Coyotes Diagonal, Br. No. 53-1193S - 56-013 Rte 2/5 Separation Bent 10, Br. No. 53-527L UTC-27 62-014 SFOBB Bent E31R, Br. No. 33-0025 UTC-09 86-01/025 Mission Ave. Via., Br. No. 57-1017R/L Bent 2L UTC-37 87-01/026 La Cienega-Venice Sep. Bent 5, Br. No. 53-2791S UTC-28 88-01

Table 5-1 - Available information matrix

30

5.1. Pile-site characteristics report

The report, written in MathematicaC format, is an overview of the pile and site characteristics for any

given site. First, it discusses the agreement between available data, e.g. SPT tests, boring logs, laboratory

testing, driving records, CPT soundings; and provides general comments on the results of the load tests,

the pile behavior, and on any other relevant information.

Next, a data quality assessment is done by assigning grade values to the data relative to a rating criteria

developed for the database. This rating has qualitative meaning only within the Caltrans dataset, therefore

it will not be considered in this study.

A description of the pile physical properties and dimensions; and soil profile follows. The parameters

reported for each layer include: Undrained Strength (psf), set to zero for sands; N values, set to zero for

clays; and unit weights (pcf).

Finally, a prediction of axial pile capacity based on SPT N values correlations is presented. For

calculation purposes, the report estimates the N values of clays based on a correlation with the undrained

strength (Olson and Shantz, 2004).

5.2. CPT profiles

The cone penetration test (CPT) profiles provide continuous readings at 0.05 m depth increments for tip

resistance (q), sleeve friction (fs), and shoulder pore pressure (u2) for all of the sites. The data is presented

in an Excel spreadsheet where the 1s column describes the depth in (meters), the 2d column the tip

resistance in (tsf), 3" column the sleeve friction in (tsf), and the 4h column the shoulder pressure, u2, in

(psi). The data was transformed into SI-units for the purpose of this study.

5.3. Load tests

Load-displacement pile tests were provided for each site. Piles MIT-4 and MIT-5 included both up-lift

and compression readings. The remaining piles only included up-lift load tests.

31

5.4. Pile and site data overview

MIT CPT Top of Top of

ID Sounding Sounding SoundingElevation Elevation

No. (ft) (m)

1 UTC-40 35 10.672 - 0 0.003 UTC-27 361 110.064 UTC-09 14 4.275 UTC-37 36 10.986 UTC-28 88 26.83

Table 5-2 - CPT soundings

MIT Surface Watertable Watertable Footing Pile top Pile Tip Pile

ID Elevation depth Elevation elevation elevation Elevation embedmentlength

(m) (m) (m) (m) (m) (m) (m)

1 8.54 1.52 4.88 6.40 7.32 -6.71 13.112 6.10 4.88 -0.61 4.27 5.79 -10.67 14.943 110.06 11.13 97.56 108.69 110.52 94.97 13.724 3.05 0.00 0.30 0.30 0.30 -12.96 13.265 10.67 2.13 6.40 8.54 9.45 -1.83 10.376 27.13 4.73 19.97 24.70 25.30 8.23 16.46

Table 5-3 - Site information

MTPile Stick Pile WallAra WihD Pile type Tip length upk embeded Pile width thicness Perimeter Area Weigh

MIT ile ype Tip engt up length

________ ____ (in) (in) (in) (in) (cm) (in) (M2) (kN)

1 PP 16x0.5 open 14.02 0.91 13.11 0.41 1.27 1.28 0.0157 16.862 PP 14x0.44 open 16.46 1.52 14.94 0.36 1.12 1.12 0.0121 15.233 HP 10x57 open 15.55 1.83 13.72 0.25 0.00 1.03 0.0108 12.904 Steel open 13.26 0.00 13.26 0.61 1.27 1.91 0.0238 24.175 Square conc. closed 11.28 0.91 10.37 0.36 0.00 1.12 0.0993 26.386 HP 14x89 open 17.07 0.61 16.46 0.36 0.00 1.45 0.0168 22.01

Table 5-4 - Pile properties

MIT Load Test Test location Uplift (mm) Compression (mm)ID 1.27 2.54 5.08 1.27 2.54 5.08

No. (KN) (KN) I (KN) (KN) I (KN) (KN)

1 38-01 North East 1068 1068 1068 0 0 02 56-01 Los Coyotes 1313 1522 1558 0 0 03 62-01 2-5 Sep 356 356 356 0 0 04 86-01/02 Bent E31 R 1246 1358 1358 2493 2737 27375 87-01/02 Mission Ave 490 614 614 1148 1148 11486 88-01 La Cienega 1513 1780 1958 0 0 0

Table 5-5 - Load-deflection tests

32

6. SOIL-PROFILE CHARACTERIZATION

The first analytical task undertaken in this study was to interpret various soil parameters for each of the

six sites based on the CPT soundings, and assess the accuracy of those results to confirm the applicability

of the CPT method.

6.1. General procedure

a) Collect all data pertaining to each of the six sites and reference it according to Table 3. Given that

the CPT soundings and the borehole information included in the Pile-site characteristics report

were referenced to different elevations, it was necessary to superimpose and align all the data

relative to a fixed datum. This was done by drawing each profile to scale in Autocad. Each sketch

includes elevations for: the CPT sounding, the surface, the top of pile, the bottom of the footing,

the watertable, the tip of the pile, and for each of the soil layers described in the borehole log. For

each of the soil layers descriptive information included the soil type, unit weight, standard

penetration blow counts (N), and undrained shear strengths.

b) Draw profile of vertical stresses ( a,.; a',O; assuming hydrostatic pore pressures, u.) based on

quoted unit weights of the borehole logs.

c) Draw CPT profiles for tip resistance, sleeve friction, and shoulder pore pressure (u2) readings.

d) Draw normalized CPT profiles: i) qc-ayo/J', 0 , ii) f,/q, and u2/qc.

e) Detect locations of clean sands, which will occur at Au = (u-u0 ) 0 and relative high values of q.

f) Detect fine grain deposits, as evidenced by high values of u2/qc (>0.7) and low values of q.

g) Label soil layers as probable sands or clays.

h) Calculate the friction ratio (f,/(qt-cor) * 100%) and classify the soil deposits according to the chart

developed by Robertson & Campanella (1988).

i) Develop correlations of tip resistance vs. depth for various relative densities, Dr. (Jamiolkowski et

al. 2001). Details are provided in section 6.1.2.

j) Develop correlations of tip resistance vs. depth for various angles of effective friction, j'

(Mayne 2005). Details are provided in section 6.1.3.

k) Calculate maximum effective past pressure for clay layers (For correlations of q, and a'p; Mayne,

2005).

1) Calculate undrained shear strength (su Dss) for estimated OCR as per Ladd (1991).

m) Calculate cone resistance coefficient Nk~ (qt-avo)/su for clay layers.

n) Graph previous results against depth, and compare them to reference values and correlations.

33

o) Iterate with more detail where applicable to classify definite soil layers.

p) Label interpreted soil profile and compare it to Caltrans profile

q) Repeat cohesionless materials graphs for relative density (i) and friction angle (j), assigning to the

clay layers a value of zero for q.

r) Repeat graphs (k),(l),(m); for clay layers assigning a value of qe equal to zero for the sand

deposits.

s) Draw interpreted soil profile with calculated soil identity parameters (s", ', Dr, etc.), and compare

it to Caltrans profile.

6.1.1. Soil classification

It was mentioned in the preceding heading that the soil profiles were classified using the chart developed

by Robertson and Campanella (1988) for CPT tests. The input parameters of the log chart are based on

the CPT readings, were the abscissa corresponds to the Friction Ratio, and the ordinate to the Normalized

Cone Resistance:

Friction ratio: " -100% (6-1)(q, o-,)

Normalized cone Resistance: q' - (6-2)

For the sake of this study, and to allow a more expedient sorting of the many data points available for

each site, the soil classification chart was digitized. This permitted superposition of the data points on top

of the digitized chart.

6.1.2. Cohesionless layers

The relative density (D,) and the angle of effective friction (4') were determined for the cohesionless

layers present in each site. These parameters, not only provide information that allows classification of

the soil deposits, but also they are input parameters of the API-00 and NGI-05 design methods review

herein.

The relative density (D,) was calculated using an empirical equation proposed by Jamiolkowski et al.

(2001), based on the earlier worked of Schmertmann (1976). This correlation relates the relative density

(D,) to the cone tip resistance (q,) and to in-situ the mean effective geostatic stress:

34

O'm = 1+2KO )- a' (6-3)3

where:

KO ~ 0.40

Om' and a', should be expressed in [kPa] to input equation 6-13.

The relative density equation was developed for unaged, uncemented silica sands of low to moderate

compressibility, and can be rearranged to calculate the tip resistance as a function of vertical effective

stress (thus depth) for selected values of relative density (equation 6-3). The results can be plotted in

design charts with a family of curves representing the range of the relative density, the outcome illustrated

in Figure 6.6.

qC =eC2D, .C 0 .(Y :)c (6-4)

where:

C2 = 2.96, C1 = 0.46, C0 * = 300

Dr = relative density (in decimals)

K,~0.40

qe and am' are expressed in [kPa]

The angle of effective friction (#') was assessed in a similar manner as the relative density. Design charts

were developed for each site, by means of an equation (6-5) proposed by Mayne (2005) based on

empirical CPT relationships developed from statistical analyses of data measured in a calibration

chamber.

#'=17.6* + I - log( U- 1 ( 6-5 )

Mayne (2005) concludes that the empirical equation compares well to measured data obtained from

results of undrained triaxial compression tests performed on high quality samples at four river sites

(Mimura 2003). The following figure illustrates the comparison.

35

a)4)

50

451

40

351

IN Yodo RiverX Natori River

- Tone RiverI----------40 Edo River

*K&M90

- -- -- - #'(deg}= 17.6 +11.0. -10

30 .- . . - -.0 100 200 3

Normalized Tip Stress, qt1

00

Figure 6.1 - Comparison of measured #' from frozen samples vs. qt (Mayne 2005)

The transformed equation that allows plotting the cone tip resistance against the vertical effective stress

for given values of angles of effective friction is presented:

( '17.6*

q ~=o, 1i 11' (6-6)

where:

qt and avo' are expressed in units of atmospheres.

Figure 6.6 includes the design charts calculated for pile MIT-4.

6.1.3. Fine grain (Clay) layers

Three parameters were determined for identification of the clay layers, these were: overconsolidation

ratio, undrained shear strength, and cone resistance coefficient. The details of their required calculations

follows.

The maximum effective past pressure (a'p) for clay layers was determined using an analytical formulation

developed by Mayne (2005) on the basis of spherical cavity expansion theory and critical state soil

mechanics concepts. The formulation relates the overconsolidation ratio (OCR = Zi) in clays to CPTV0

parameters in the following simplified form for intact clays:

36

a

o-'P = 0.33-(q, -o-) [

Mayne (2005), indicates that the validity of equation (6-7) was confirmed by statistical analysis of

piezocone-oedometer data in a variety of clays. Figure 6.2 illustrates the agreement in the data.

100W0

ow

1100

100

Figure 6.2 -

1000 10000Net Cone Restdtmice, q,-a, (IWO.)

Preconsolidation Stress in Clay from Net Tip Stress (Mayne 2005)

The undrained shear strength (su) was calculated following the empirical equation presented by Ladd and

Foot (1974) and Ladd (1991), which correlates a power function of the overconsolidation ratio (OCR =

a,'/ av') and the effective stress of the clay; to its undrained shear strength ratio.

(( I/DSS=S-OCRm (6-8)

where:

S = undrained strength ratio of K0 normally consolidated clay

m= is an empirical coefficient

Extensive correlations (Ladd, 1991) show S = 0.22, and m = 0.80.

The cone resistance coefficient (Nk) is proportional to the ratio of the net tip resistance and the undrained

shear strength as indicated in the following equation.

Nk ( t -avoJNk *SU

(6-9)

Empirical correlations established from undrained shear strength measured in direct simple shear tests

(su DSs) report values of Nk that vary in a range of 15 ± 5. The quoted range for Nk implies that the

37

tit

[kPa] (6-7)

undrained strength can vary is as much as 50% (Whittle, 2005). Nevertheless, in this study, the cone

factor, Nk, is used to confirm the existence of clay deposits based on piezocone readings that provided

results within the mentioned range, and not to provide insight on the value of the undrained shear

strength, which was estimated beforehand. Under this premise, the applicability of Nk in this investigation

is validated

6.2. Site interpretation results

The outcome of the interpretation of the soil profiles is presented in a set of charts and a diagram that

illustrate the main findings of the investigation, and that define the profile that will be used for predicting

the axial pile capacity for the methods under consideration in this study. The site investigation

information for each pile location consists of the following documents:

* Pile-soil elevations diagram

* Chart A - Vertical profile, CPT readings

* Chart B - CPT normalized profiles

* Chart C - Internal friction angle and relative density graphs

* Chart D - Undrained strength (se) Cone Resistance Factor (Nk), Overconsolidation Ratio (OCR)

* Chart F - Soil Classification as per Robertson and Campanella (1988)

For the sake of illustration, a detailed description of the site interpretation results for pile MIT-4 will be

presented in the main body of this document, whereas for the remaining piles only a summary will be

presented, their corresponding set of detailed charts can be found in the Appendices.

6.2.1. Pile MIT-4

Section 6.2 - Site investigation results, indicated that six diagrams are produced as the result of the site

interpretation for each pile. These diagrams are included in this section for pile MIT-4 with a detailed

description of their main findings. The descriptive sequence of the interpreted soil profile and the

presentation of the diagrams will start at the pile top and move toward its tip.

Pile MIT-4 is a 13.26 m long, 0.61 m in diameter open-ended steel pipe (Figure 6.3). The pile top is

located at elevation (El.+0.30 in), under approximately 4 meters of a hard material that comprises a

38

compacted fill. This layer acts on the pile solely as overburden. The water table elevation provided by

Caltrans is near the pile top at elevation (El. +0.3 m), (Figure 6.3).

Below the fill, there is a 4 m thick recognizable layer of sand (El. +0.30 m to El -3.88 in). In this layer the

pore pressures readings (u2), Figure 6.4d, indicate that the excess pore pressures created by the piezocone

penetration is almost zero (Au = u2-u0 ~ 0),which is typical behavior of clean sands; additional

confirmation, is provided by the high readings of the tip resistance (qc) in Figure 6.4b; and the low values

of the normalized pore pressure factor (u2/qc) in Figure 6.5c. Review of the relative density (Dr) and angle

of internal friction (b') correlations of section 6.1.2, are presented in Figures 6.6a and 6.6b, respectively.

These data indicate that the layer comprises two recognizable subunits. The first layer (El. +0.42 m to

El. -1.23 m) exhibits "lower strength" compared to the denser layer below (El. +1.23 m to El -3.88 in),

Figure 6.3. The Robertson and Campanella (1988) soil classification ranks these layers as group 6: Sands

- Clean sand to silty sand, as can be appreciated in Figure 6.8b for their corresponding elevations. The

interpretation of this layer as sand matches almost identically with the profile interpreted by Caltrans,

Figure 6.3.

From elevation (El. -3.88 m and El. -9.43 m) there is a layer where the tip resistance readings drop to

small values, while excess pore pressures develop (Figure 6.4b and 6.4d). For this layer the normalized

pore pressure factor (u2/qc) in Figure 6.5c reaches ratios higher than 0.4. The previously described

behavior is expected for clay layers. The existence of a clay layer is confirmed by the calculated

undrained shear strength, of approximately 45 kPa (Figure 6.7b), which is very close to the values

measured in laboratory UU-tests by Caltrans and included in Figure 6.3. The cone resistance factor for

this layer (Nk = 15) are exactly on the average of the reported values in the literature (Aas et al. 1986).

Robertson and Campanella (1988) classify this layer as group 3: Clays - Clay to silty clay. Figure 6.8b

illustrates that there is very small variation in the input parameters for the soil classification, and that the

values are clustered together well into the clay groups (Groups 3 and 4); providing un ambiguous

evidence of the existence of clay (Figure 6.8).

Below the clay layer, (i.e. below El. -9.43 m) there are 4 meters of variable tip resistance (Figure 6.4a)

that indicate the existence of a layer of increasing density, with traces of a weaker material (e.g. El. -12.00

m). The readings of excess pore pressures (Figure 6.4d) indicate that this layer does not effectively

dissipate the excess pore pressure created by the piezocone probe, thus indicating that the layer is not a

clean sand. The normalized pore pressure factor (u2/qc) included in Figure 6.5c, decreases rapidly from

ratios of 0.4 to almost zero, indicating that the presence of cohesionless materials increases with depth.

39

This appreciation is confirmed by the classification of Robertson and Campanella (1988). From elevation

El.-9.43m to El.-10.93 m it ranks the layer as group 5: Sand mixtures, from El.-10.93 m to El. -11.98 m as

group 6: Sands, then from El. -11.98 m to El. -12.13 m as group 3: Clays, and at the bottom of the layer

from El. -12.13 to El. -13.38 as group 6: Sands, as indicated in Figure 6.8b. From the previous description

it is concluded that this layer comprises a sand matrix that increases its density with depth, with an

embedded thin clay layer at El. -12.00 m. The relative density (Dr) and angle of internal friction (')

correlations (Figure 6.6a and 6.6b) provide the means for subdividing the sand matrix into three sub-

layers that match the elevations described in the Robertson and Campanella (1988) classification and that

are illustrated in Figure 6.3. The embedded clay layer at El. -12.00 m is thin but exhibits stiff properties.

The calculated measured of undrained shear strength (Figure 6.7b) varies between 150 kPa and 300 kPa,

but given the small of the clay layer, a lower value of 150 kPa is assigned to this layer. The Caltrans soil

profile fails to recognize this clay layer, this is expected, as its site exploration was performed during the

execution of the standard penetration test, in which sampling occurs at intervals larger than the clay layer.

It should be noted that the pile tip is located in this sand matrix layer, at elevation -12.96 m.

From El. -13.38 m to El. -15.08 m, the cone tip resistance increases continuously, indicating the presence

of sands. This is confirmed by the normalized pore pressure factor (u2/qc) in Figure 6.5c, where the ratios

are equal to zero. Robertson and Campanella (1988), Figure 6.8b, classify this layer as group 6: Sands.

The relative density is estimated using the Jamiolkoski et al. (2003) correlation at 80%. The angle of

internal friction is estimated at 43 degrees (Figures 6.6a and 6.6b).

At the bottom of the CPT exploration data a 0.5 m thick clay layer can be identified on top of the

beginning of a sand layer. The clay layer is identified by the low values of cone resistance (Figure 6.4a)

and by the Robertson and Campanella (1988) classification. Figure 6.3 includes both the Caltrans and the

interpreted profile, together with the significant pile elevations and characteristics.

40

Pile - ID # 4Type of pile: Steel pipe pileEnd condition: Open endedDiameter: 0.61 mThickness: 0.5" (1.27 cm)Base area of pile: 0.0238 m2Perimeter: 1.91 mWeight of pile: 24.17 kN

CPT Top +4.27

Surface

Top of pileBott. footingWater table

+3.05

+0.30

D)

Elevations(m)

Pile tip -12.96

CPT Tip -15.63

2.75

I . ,- q

0.61 --

13.26

+0.30

-3.96

-9.15

-11.59

-13.72

-15.85

CALTRANS Soil Profile

Soil Ysail N Sutype [kN/m3] [bpf] [kPa]

- 19 - -

Fill 18.8 - -

Sand 18.4 21 -

Clay 14.9 - 42.50

Sand 19.5 26 -

Sand 20.4 43 -

Sand 20.4 49 -

+4.

+2.+2.

+0.

-1.2

-3.8

-9.4

-10.

-11.-12.

-13.

-15.-15.-15.

Interpretation based on CPT

Soil * Dr su

27 type [0] [o [kPa]

Fill - - -

577 Clay - - 20

Sand 40 60 -

42

Sand 38 50 -

3

Sand 40 55 -

8

Clay - - 42.50

3

Sand 38 40 -

93Sand 40 65 -

9813 Cla - - 150

Sand 43 80 -

38

Sand 43 80 -

08 7T4 Clay - - 12563 jSand 38 45 -

Figure 6.3 - Pile MIT-4- Pile-soil elevations diagram

41

MIT-4 MIT-4

200 400 0 20,000 40,000 60,000 0

MIT-4

500

MIT-4

1000 -100 400 900 14005.

4.

3

2

1

0*

-1 -

-2

-3.

-4

-5.

-6-

-7.

-8

-9

-10

-11

-12

-13-

-14-

-15-

-16-

, I

' I

, --- U0 ' '

5

4

3

2

1

0

-1

-2

-3

-4

-5

-6

-7

-8

-9

-10

-11

-12

-13

-14

-15

-16

- - - uO --- s'vo -- svo, kPa]

I I

I I

I I

I I

I I

I II I

I I

I I

I I

I II I

I I

I II I

I I

I I

I I

I I

I I

I II I

-Tip resistance (qc), kPa

5

4

3

2

1

0

-2

-3

-4

-5

-6

-7

-8

-9

-10

-11

-12

-13

-14-

-15

-16

-Sleeve friction (fs), kPa]

5

4

3

2

1

0

-1

-2

-3

-4

-5

-6

-7

-8

-9

-10

-11

-12

-13

-14

-15

-16

I II I

I I

I I I

I I

- I I

I I

I I- I I I

I I I

I II I

I II I

I I

I I

I I II I

I I II I

I I I

I I I

I I

I I

* II I

S I

U I

* I I

I I

I I£ I

I I II I I I

I I I

I II I I I

I I

* I I II I I

- Pore pressure (u2) - - - uo, kPa

Figure 6.4 - Pile MIT-4 - Chart A - Vertical profile, CPT readings

42

0

d

C-

[j

MIT-4

0 100 200 300 400 500

MIT-4

0.000 0.050 0.100 0.150

MIT-4

-0.100 0.150 0.400 0.650 0.9005

4

3

2

0

5-

4-

3

2.

1

0

-1

-2-

-3

-4-

-5 -

-6-

-7-

-2

-13-

-14

-15-

-16

-4

-3 -

-4

-5U

-6

-7

-8

-9

-10

-11

-12-

-13

-14

-15

-16

E

w

-12

-13

-14

-15

-16

- -fsqcI-(qc-sv)/s'vo I |--- u2/qc |

Figure 6.5 - Pile MIT-4 - Chart B - CPT normalized proffies

43

MIT-4 - Correlation depth vs qc [kPa] for various 0'(Mayne 2003)

0 10,000 20,000 30,000 40,000 50,000 60,000

432

1:~ 1 V0

-11-1 :T6

-3--4--5-6

-8-9

-10-11-124

A-13-144

-15 4-16

34 36 38 40 42 44 46 =0'(*)

-30 -32 - - -34 -- 36- 38 40 i 42 - 44-46 -- 048 - qc, kPa

MIT-4 - Correlation z vs q, [kPa] for various D,(Jamiolkowski 2003)

0 10,000 20,000 30,000 40,000 50,000 60,000

543

2

0

-2

-31

-4--5-6

-8

-10-11-12-

-13-14-15

-1640% 50% 60% 70% 80% 90% 100% =D,

0.1 - 0.2 - 0.3 0.40.5 0.6 0.7 0.8

' 0.9 1 - qc,kPa

Figure 6.6 - Pile MIT-4 - Chart C - Friction angle and relative density for cohesionless layers

44

C0

a)

MIT-4

0 100 200 300 4005

4

3

2

0

-1

-2

-3

-

-5 - 1

-6-74

-8I

-9I

0 I

-12

13 0 -

-14 o'vo

-15

-16

- - -U0 -s'vo - svo

MIT-4 -SuDSS

0 100 200 300

4.

3-

2

0

-2

-3-

4 4

-6

-7.

-8

-9

-10

-112

-13

-16

su Caltrans su Interpreted, kPa

MIT-4 - Nk

0 10 20 305

3 I4

3-.

11

-1

-2

-3

-4

-50

-61

-,--10

-11

-12

-3

-4

-5

-16

-Cone Resistance Factor

MIT-4 - OCR

0 5 10 15 205-

4

3

2

0-

-1

-2

-3

-4

-5

-6

-7-

-8

-9

-10

-11

-12

-13

-14

-15

-16

I II I

I I II I

-, I I

I I II I

I I II I I

I I I II I I I

I I II I

I I II I

I I II I I

I I

I I I II I I

I II I

I I I II II I I II I II I I II I I

I II I I

I I I II I I II I II I I

I II I I

I I I II I I II I I I

I I I

E~i~Figure 6.7 - Pile MIT-4 - Chart D (Undrained strength and stress history of clay layers)

45

100

10

::1q 7

1000

I1 1 1 Vl .- I- 94

0

>

.U

0cCu-U

0

100.1

Friction Ratio fIs/(qc-v 0)

1. Sensitive Fine Grained2. Organic Soils -Peats3. Clays - Clay to silty clay4. Silt mixtures - Clayey silt to silty clay5. Sand mixtures - Silty sand to sandy silt6. Sands - Clean sand to silty sand7. Gravelly sand to sand8. Very stiff sand to clayey* sand9. Very stiff fine grained*

*Heavily overconsolidated or cemented

1

MIT-4 - Soil Classification(Robertson & Campanella, 1988)

At~ 1

1 K 1-4

5e

3--

0 10 100

--- fs/(qc-svo) - (qc-sv)/s'vo

Figure 6.8 - Pile MIT-4 - Chart E - Soil Classification (Robertson and Campanella, 1988)

46

1000 10000

E

0

Cu

8

5

4

321

0-1-2

-3-4

-5-6-7-8

-9-10-11-12

-13-14

-15-16

-j - i i --L -L;; --L -k -L - -L~

SI I I I t i l

-1 61.616 W - 6 1 .1 - - .6. -6 .6 1 61 .

I 1 , 1 i l l I I I I I I ] I I I I t l

I N ak I I I I I Iti l 1 1 1 1 1 1 1 1 ]

- .- , ,, r-r- - , r, -i-i, ri - - -, , * - r

I I I i l Ii I I I I M l I I I I l I I I I t i l l

I I II I I l l I il I I I I I IT7 "T 1_-

11

6.2.2. Pile MIT-1

In pile MIT-1 the CPT readings end just beneath the tip, providing enough data to interpret the profile

along the pile's length. This pile is a 13.11 m long open-steel pipe pile with a diameter of 0.41 m (Figure

6.9)

There is a poor agreement between the Caltrans and the author's interpreted profile, specifically in the

location and width of the clay layers. The Caltrans profile indicates that the site consists mostly of sand

layers with one clay deposit of approximately 1.20 m thick, located below elevation -3.35 m. This clay

layer corresponds to 9.3% of the total pile's embedded length (13.11 m). In contrast, the interpreted

profile indicates the existence of seven clay layers that equate a total thickness of 9.43 m or 72% of the

pile's embedded length (Figure 6.9). Refer to Appendix B for detailed site investigation charts.

The disagreement between the two interpretations arises due to the peculiar behavior of the site

investigation data, which borderlines the definition between sands and clays for many of the encountered

layers. The findings can be summarized as follows:

* Most of the cone tip resistances (q) indicate the existence of soft deposits. Few layers exhibit

high values of qc commonly found in clean sand deposits.

" The measured pore pressure (u2) is shifted from zero into negative values indicating the existence

of fine grained deposits. The u2 profile increases with depth following a slope that resembles the

assumed hydrostatic pore pressure and for most of the site Au = (u-uO) constant.

* The ratio u2/qc does not provide conclusive results, on the contrary, most of the readings are low,

between - 10% and +10% suggesting the existence of coarse deposits, quite the opposite to the

measured pore pressures u2. There are a few "peaks" that confirm the existence of fine grained

deposits where pore pressure created by the CPT cone were not dissipated.

* The measure sleeve friction (f,) is relatively constant along the entire site, with the exceptions of

the clay layer at elevation +4.00 m and the sand layers at the pile's tip.

* The relative density and angle of internal friction were preliminary calculated for the entire length

of the pile, as if all the layers were sand, the results indicated that most of the pile encounters

loose material and confirmed the existence of the clean clay layer (very low values of Dr).

* The Robertson and Campanella (1988) soil classification ranks most of the site as: "Silt mixtures

- Clayey silt to silty clay", it also confirms that there are clean sands at the pile's tip and a few

layers of clean clays (Please refer to Appendix for detailed chart).

47

9 The calculated values of undrained shear strength and cone factor are slightly higher than the

typical values of clay layers, but in range of the expected accuracy of their predictions.

* It was concluded that the site is dominated by materials classified as silt mixtures.

* It was noted that the soil profile follows a repetitive layering pattern; a sand layer, on top of a

silty clay layer, and so on. The layers are relatively thin, and could potentially conduct water

efficiently, thus explaining the resemblance of the measured pore pressures (u2) to the assumed

hydrostatic condition.

0 The shift of the u2 profile into negative values can be arguably explained to occur because of the

existence of a clay layer at exactly the location of the start of the shift. This layer can hinder the

supply of water to lower layers.

Pile - ID # 1

Type of pile:End condition:Diameter:Thickness:Base area of pile:Perimeter:Weight of pile:

CPT Top +10.6

Surface

Top of pile

+8.54

+7.32

Bottom of +6.40footing

Water table +4.87

Elevations(m)

Pile tip -6.71CPT tip -6.88

Steel pipe pileOpen ended0.41 m0.5" (1.27 cm)0.01 57 m21.28 m16.86 kN

7 --T- - -

0LU-

14.03

0.92

13.11

- 0.41

+10.67

+8.54

+6.40

+4.42

+2.13

+0.61

-2.13

-3.35

-4.57

-5.18

-5.79

-7.01


Soil ysoI N Sutype [kN/m3l [M*A [kPal

- 19 - -

Fill 18.8 - -

Sand 19.6 11 -

Sand 20.04 28 -

Sand 20.1 21 -

Sand 19.6 11 -

Sand 20.1 27 -

Clay 18.8 - 35.91

Sand 20.4 50 -

Sand 19.8 18 -

Sand 20.9 72 -

+10.67

+8.67

+7.82+7.57+7.42

+6.37+6.17

+5.27

+4.62

+3.27

+0.12

-1.08

-2.28

-3.23

-4.10

-4.98-5.38

-6.23-6.88


Soil 0 Dr SUtype [01 1%] [kPa

Fill - - -

Sand 34 20 -

4~- - 901-ana 34 20 -

Clay - - 90-Sand 34 30 -

Clay - - 90

Sand 36 35 -

Clay - - 60

150Clay

Sand

ClaySand

an

38

40

40

45

60

Clay - - 125

Clay - - 90Sand 42 70 -

Clay - - 175

Sand 44 80 -

175

-l -o

Figure 6.9 - Pile MIT-1 - Pile-soil elevations diagram

48

The interpreted site profile for pile MIT-I concluded that 72% of its length is comprised of silt mixtures,

and not of sand materials, which is the scope of this thesis. Nevertheless, this pile will be considered into

the calculation stage that follows in the next chapter, in order to provide more insight into the

interpretation of the soil profile using piezocone data.

6.2.3. Pile MIT-5

Pile MIT-5 is a 0.36 m wide, 11.26 m long, square closed-ended concrete pile. The pile has a length of

embedment of 10.35 m after its tip, located at El. -1.83 m (Figure 6.10).

The surface elevation at the pile location is El. +10.67 m., slightly lower than the location were the CPT

test was performed and that is about 10 m away. The bottom of the footing, which is the effective pile top,

is located at elevation El. +8.54 m. The water table is located at El. +6.40 m (Figure 6.10).

The overburden layer comprises of a 2.5 m deep fill layer with a unit weight of 18.80 kN/m3 as reported

by Caltrans (Figure 6.10).

Below the fill, from elevation +8.54 m to + 4.53 m, three distinct layers of sand are encountered. These

layers exhibit typical cohesionless behavior: the measured cone tip resistance values are relatively high;

the excess pore pressures created by the piezoprobe cone are almost zero (Appendix B - Chart A); and the

normalized pore pressure factor (u2/qc) is close to zero (Appendix B - Chart B). Robertson and

Campanella (1988) define these layers from higher to lower elevation as Sand mixtures, Sand, and Sand

mixtures, respectively. The calculated measured relative density and angle of internal friction, confirms

that the layer in the middle (El. +7.73 to El. +5.5 8) is denser than the two boundary layers. Figure 6.10

presents their calculated soil properties.

Under the sand layers, from elevation El. +4.53 m to El. +1.38 m, an interlayer system of sands and clays

is encountered. This repetitive pattern can be clearly identified from the piezocone data:

* The average values of the cone tip resistance drop, in comparison to the previous sand layers.

There is an increase in variability in the cone tip measurements, the low values correspond to the

clay layers, and the high values to the sand materials. (Appendix B - Chart A).

49

" Excess pore pressures develop and follow an constant average trend. At the location of the sand

layers, the excess pore pressures reduce, and therefore "peaks" occur, i.e. El. +3.25 m (Appendix

B - Chart A).

" The normalized pore pressure factor varies significantly, from values of 0.4 typical in clay, to

values near to zero and common to sands. (Appendix B - Chart B).

" The calculated values of cone factor (N) for the clay layers varies from 15 to 22, a range that is

common to clays (Aas et al. 1986). (Appendix B - Chart D).

" The calculated relative densities calculated for the sand layers classify them as medium dense

sands, with an average value of 40% (Appendix B - Chart C).

" Confirmation of the classification of this soil layers is provided by means of Robertson and

Campanella (1988) in Chart D of the Appendix B.

Figure 6.10 summarizes the soil properties for this interlayer system.

From elevation El. +1.38 m until the tip of the CPT sounding at elevation El. -1.62 m, four sand layers are

identified. The classification of these layers as sand conforms to the cone tip measurements readings that

exhibit a constant increase from elevation E. +1.38 m downward. For that same location the excess pore

pressures measurements, and the normalized pore pressure factors drop to zero. (Appendix B - Chart A

and Chart B). The definition of four different layers, corresponds to their increase in relative density,

which can be clearly identified from the calculated values of relative density as per Jamiolkowski et al.

(2003) in Appendix B - Chart C. The upper layer exhibits Dr = 40%, while the lowest layer an average

value or 70%.

At the tip of the CPT sounding, i.e. El. -1.62 m, the values of cone tip resistance drop and excess pore

pressures develop, nevertheless, the normalized pore pressure factor remains with values close to zero. It

can be argued that the underlying material below the previously described sands, is clay. There is not

enough information to confirm this assumption.

In general terms, the Caltrans profile and the interpreted profile, agree on the location of the upper group

of layers of sand, as well on the lower group. (i.e. El. +8.54 m to El. +4.53 m, and El. +1.38 m to El. -1.62

m respectively) as indicated in Figure 6.10. Both interpretations agree, for both of those sand group

layers, on an increasing trend of sand strength with depth. This fact can be identified by comparing the

calculated relative densities and angles of internal friction with the reported Caltrans N-values (Figure

6.10)

50

The Caltrans profile fails at identifying the interlayer system of sand and clay materials between elevation

El. +4.53 m and El. +1.38 m.

Please refer to the Appendix B for the detailed site investigation charts.

Pile-ID#5

Type of pile: Square concrete pileEnd condition: Closed endedDiameter: 0.36 mThickness: -Base area of pile: 0.0993 m2Perimeter: 1.12 mWeight of pile: 26.38 kN

CPT Top +10.98Surface +10.67

Top of pile +9.45Bottom offooting +8.54

Water table +6.40

a0I-a-0

Elevations(in)

CPT tipPile tip

0

-1.62-1.83

0.91

0.36 -

10.35


Soil ysoil Ntype oimzl [bpfl

+10.67 1

+8.54

+7.62

+6.71

+5.49

+4.57

+3.96

+2.44

+0.91

+0.30

-0.30-0.91

-1.52

18.80

19.8

19.8

20.1

Sand 19.8 9

Sand 19.8 7

Sand

Sand

SandSandSandSand

Sand

20.1

20.4

20.4

20.4

20.4

20.4

20.4

12

20

28

35

56

34

12

-3.05 ' I I


Soil I ' Dr Sutype [0] [% I [kPaJ

+10.98

+8.54

+7.73

+5.58

+4.+4.38+3.83

+3.13+2.73+2.38+2.18+1.38

+0.98+0.28-0.12

-1.62

Figure 6.10 - Pile MIT-5 - Pile-soil elevations diagram

51

Fill - - -

Sand 38 45 -

Sand 40 55 -

Sand 38 40 -

- - 155 F-

Sand 36 30 -

Clay - - 110Sand 38 45 -

JSand 36 30 -

Clay - - 100

Sand 38 40 -

and 40 60 -

Sand 41 65 -

Sand 41 70 -

-- a

Fill

Sand

Sand

Sand

8

8

14

6.2.4. Pile MIT-2

The "Pile-site information report" provided for pile MIT-2 did not agree with the CPT readings. It was

found that those CPT readings correspond to a different site, and therefore this pile will not evaluated in

this study.

6.2.5. Pile MIT-3

For this pile the CPT readings cover 74% of the total length of the pile measured from the top. The scope

of this document requires for axial prediction purposes that the CPT data should cover at least the entire

length of the pile, therefore this pile will not be considered in the axial capacity predictions of this study.

Please refer to the Appendix for the detailed site investigation charts.

6.2.6. Pile MIT-6

For this pile the CPT readings cover 69% of the total length of the pile measured from the top. The scope

of this document requires for axial prediction purposes that the CPT data should cover at least the entire

length of the pile, therefore this pile will not be considered in the axial capacity predictions of this study.

Please refer to the Appendix for the detailed site investigation charts.

52

7. AXIAL PILE CAPACITY PREDICTION

One of the features of the piezocone data is that they provide a continuous penetration record that can be

incorporated directly into the design process for pile foundations. In this study, the piezocone data are at

0.05 m intervals through the length of the pile. This resolution provided 300 to 400 calculation data points

for each pile. To take advantage of this information, and to avoid averaging techniques for each soil layer,

a spreadsheet program was developed in Microsoft's Excel. The spreadsheet was designed to efficiently

process the CPT readings, compare and relate the elevation datum, and predict the axial capacity of each

pile for the 5 methods under consideration in this thesis.

This chapter presents the results of the predicted axial capacity, for piles MIT-4, MIT-5 and MIT-1,

calculated following the guidelines of the CPT design methods described in Chapter 4. The predictions

include tension and compression type of loading for each pile. First, the calculation procedure is

described, followed by the graphical representations of the results.

7.1. Spreadsheet input data

The spreadsheet requires the input of:

* The characteristics of the pile: dimensions, elevations, and material properties.

* The site description: surface and water table elevations, and height of overburden material.

* The CPT readings: tip resistance, sleeve resistance, shoulder pore pressure.

* The classification of each data point as either cohesionless (sand), or fine grained (clay) material.

The classification of the soil follows the procedure described in Chapter 6.

7.2. General calculation procedure

The calculation procedure performed by the spreadsheet can be summarized in these steps:

* Insert input data as indicated in section 7.1

* Compare the input elevations and adjusts them to a common datum

* Determine width of overburden layer, defined as soil that contributes to the vertical stress but has

no effect on the side friction of the pile.

" Assign unit weights for each layer (a default value y = 19 kN/m3 is used if no data is provided)

" Assign interface friction angle (6,) for ICP and UWA method. (default value, 6, = 29 0 , if no

data available)

53

* Calculate relative density (Dr) for the NGI method and compare it with the prediction by

Jamiolkowski et al. 2001 (Section 6.1.2).

* Calculate small strain modulus for ICP and UWA methods, compare results (Section 4.3.1)

* Calculate unit shaft friction for cohesionless materials

* Calculate unit shaft friction due to contribution of clay layers (Section 7.3)

* Calculate shaft pile capacity for five design methods

* Calculate end bearing capacity for 10% pile diameter displacement (qbo.1) for 5 design methods

* No plug formation was considered in excess to those guidelines included in the design methods

. Average tip resistance over ± 1.5 D for calculation of tip resistance

* Average tip resistance following the Dutch method for the UWA method (Section 4.5.1)

* Calculate pile tip resistance

* Display figures for unit shaft capacity and axial load distribution for both tension and

compression loading

* Calculate pile's weight

* Display predicted axial pile capacities minus pile weight on corresponding measured load-

deformation test curves

7.3. Clay layers - Load contribution

The approach adopted for calculating the contribution of clay layers to the shaft pile resistance was to

estimate the unit shaft resistance (-rf) from the CPT's cone tip resistance (q) and control the result, by

comparing it to the unit shaft resistance as calculated from the undrained strength.

Lehane et al. (2000) indicate that the unit shaft resistance, ry, varies approximately between the ratios of

qg/20 to qt/50 in (kPa). The precise ratio was estimated by calculating the unit shaft resistance following

the guidelines of the American Petroleum Institute for cohesive soils (API, 1993) that are based on

Randolph and Murphy (1985):

rf =0.5 -(sn - O)05 for su/a'vo < 1 (7-1 )

r0 =0.5 -s' 0.25 for su/a'v. > 1 (7-2)

It was found that unit shaft friction contributed by the clay layers in pile MIT-4 best fitted the ratio qt/25.

54

In pile MIT-5 the best comparison was achieved by the ratio q,/50. Both values fall within the limits

indicated by Lehane et al. (2000).

7.4. Spreadsheet output

The spreadsheet produces a summary of the predicted axial pile capacities for each of the five methods at

each pile site, the output includes:

* Table summarizing pile's axial capacity predictions (e.g. Table 7-2)

* Plot of the predicted and measured axial pile capacity under tension (e.g. Figure 7.1)

" Diagram of axial load distribution and unit shaft friction for tension loading without correcting

for pile's weight (e.g. Figure 7.2)

" Plot of the predicted and measured axial pile capacity under compression (e.g. Figure 7.3)

" Diagram of axial load distribution and unit shaft friction for compression loading without

correcting for pile's weight (e.g. Figure 7.4)

7.5. Pile MIT-4 capacity prediction

Pile MIT-4 is a 0.61 m in diameter steel open-ended pipe with an embedded length of 13.26 m. Section

6.2.1 presented the site interpretation for pile MIT-4, its corresponding soil profile and soil properties are

included in Figure 6.3. The following table (7-1) summarizes the soil profile by main soil groups, as sand

and clay; it is evident that the pile is surrounded by more sand layers than clays', but in very close

proportion. This table, when compared with the estimated shaft resistance for each soil group, will

provide information on the relative contribution of the normalized friction, i.e. average layer pressures on

the shaft of the pile.

Layer Thickness (%)(M)

Sand 7.56 57%

Clay 5.70 43%

Pile embedment: 13.26 100%

Table 7-1 - MIT-4 - Coverage of pile embedment per layer

It must be indicated that only external shaft friction was considered in the pile capacity predictions. Some

of the design methods claim to include plug formation into their formulation (e.g. UWA-05 and ICP-05);

55

therefore, to provide and unbiased evaluation of their performance, no analysis on plug formation was

considered.

The following table summarizes the predicted pile capacity for each of the five design methods under

tension and compression loading. It includes the predicted load for each soil group layer (kN) and its

contribution to the total load as percentage (%). For compression loading, the estimated tip bearing

capacity is indicated separately. Table 7-2 provides the value of the load test, the ratio of calculated axial

load to measured load (QcaIc/Qtest), and an average of the predictions of all design methods.

Load condition API-00 FUGRO-05 ICP-05 NGI-05 UWA-05 Load Test Averages(kN) (kN) (kN) (kN) (kN) (kN)

Tension

Sand - shaft 843 1103 824 579 870 84462% 68% 62% 53% 63% 62%

Clay - shaft 508 508 508 508 508 50838% 32% 38% 47% 37% 38%

Weight of pile -24 -24 -24 -24 -24Pile capacity: 1326 1587 1307 1063 1353 1358 1327

Qcalc/Qtest = 0.977 1.169 0.963 0.783 0.997 1.000 0.978

Compression

Sand-shaft 843 1384 1120 753 1159 105223% 35% 36% 27% 40% 32%

Clay - shaft 508 508 508 508 508 50814% 13% 16% 18% 17% 16%

Tip bearing 2361 2024 1455 1508 1240 171864% 52% 48% 55% 43% 52%


Qcalc/Qtest= 1.347 1.422 1.117 1.003 1.053 1.000 1.188

Table 7-2 - Pile MIT-4 - Pile axial capacity overview

The first conclusion that can be drawn by comparing Table 7-1 and Table 7-2, is that the sands layers

provide a higher load resistance per unit area than the clay layers. This can be identified by comparing the

coverage of each layer and its load contribution, e.g. the sand layers in pile MIT-4 cover 57% (Table 7-1)

of the pile's length, but in average, they provide 62% of the pile axial capacity in tension (Table 7-2).

This is not surprising, as the identified clay layer (El. -3.88m to El. -9.43m) has a relatively low undrained

shear strength (Figure 6.3).

The variation of the ratio (Qcaic/Qtest) in tension is smaller than in compression; in tension the average of

the ratios of prediction to measured values is 0.978, while in tension it is 1.118 (Table 7-2). The increase

in variation in the compression mode is caused by the uncertainties that are involved in predicting a plug

56

formation at pile's tip. The calculated average contribution of the tip is 52% of the load loading capacity

of the pile in compression (Table 7-2).

Each mode of loading, i.e. tension and compression, will be analyzed in further detail with the

presentation of the spreadsheet results in the next sections.

7.5.1. Tension loading

The predictability of the design methods will be presented in this section by introducing the spreadsheet

results illustrated in Figure 7.1 and Table 7.2.

The pile test load-displacement measured curve includes the results of the predicted axial pile capacities

(Figure 7.1). It can be seen in Figure 7.1, that the behavior of the pile in up-lift is somewhat ductile. It

starts picking up load at an increasing rate, yielding is reached at a displacement of approximately, 6 = 20

mm, and a measured load of 1358 kN. In terms of pile diameters, the yielding displacement corresponds

to a ratio of 5/D = 3.28%; in terms of pile length: 5/L = 0.15%. The first unloading-reloading cycle

included in Figure 7.1 suggests that the plastic deformation at yielding should be close to 15 mm. Note

that the slope of the unloading cycles are very flat compared to the original loading slope.

MIT-4 - Pile Load Test Tension (ID 86-02) Load (kN)

0 200 400 600 800 1000 1200 1400 1600

5 . 1_ _ _ _ __. I I . I . I I .

5

10

1E - Load test:138k

API : 1326 kN20 20 -- FUGRO :1587 kN

A- ICP :1307 kN

25 --- NGI :1063 kN-O-UWA :1353 kN

30

40

Figure 7.1 - MIT 4 - Tension load test and predicted axial capacity

57

Three methods (UWA, ICP and API) provide very close estimates of the total axial capacity, on the other

hand, NGI under predicts the capacity and FUGRO over predicts it (Figure 7.1).

Figure 7.2 provides the predicted shaft capacity under tension and the corresponding unit shaft friction.

The following observations can be made:

" API-00 under predicts the contribution of the lower sand layers, this is indicated by the low shaft

friction between El. -11.00 m and El. -13.00 m in Figure 7.2b, and the load axial contribution of

those layer in Figure 7.2a. Under prediction is expected as this method imposes a limiting value

of unit shaft friction. The opposite conclusion can be drawn for the upper layer of sand (Figure

6.3) near the pile top, where the API-00 method over predicts the contribution of those layers in

comparison to the other methods. This behavior is expected, as the API-00 does not account for

friction fatigue effects.

" Overall API-00 provides a good prediction of the pile axial capacity QcaIc/Qtest= 0.977 (Table 7-2)

" FUGRO-05 provide an upper bound prediction along the entire length of the pile (Figure 7.l a),

this behavior is accentuated at the pile tip where the FUGRO method excludes friction fatigue

considerations for elevations less than h = 4R* (Equation 4-5).

* NGI-05 follows a similar trend as API-00 for the lower sand layers (Figure 7.2a), but it differs in

the upper layers, where it becomes more conservative. In terms of total capacity NGI-05 is most

conservative of all methods with a ratio of Qalc/Qtest= 0.783 (Table 7-2).

" ICP-05 and UWA-05 provide very similar results of total predicted capacity (Table 7-2). They

follow a common trend in axial load distribution, but differ in the contribution of the sand layer

between elevations, EL. -11.00 m and EL. -12.00 m (Figure 7.2).

" All of the methods predict that the lower sand layer (i.e. below El. -9.43 m), contribute to 50% of

the total axial capacity of the pile. These layers have a total thickness of 3.50 m (27% of the total

embedded length of the pile).

" The methods provide greater variation in calculated unit shaft friction in sands with increasing

relative density, as can be observed by comparing the soil profile in Figure 6.3 and Figure 7.2b.

In the upper looser sands, the variation is less than 15 kPa, while at the tip it exceeds 100 kPa.

58

MIT-4 - Axial load distribution - Tension - SAND+CLAY [kN]

0 200 400 600 800 1000 1200 1400 1600

I I I

I I I I

I I I I I

I I I I I

- II

-A I a- Fgo ~i lP- '- G -.- W

18001.00

-1.00

-3.00

-5.00

-7.00

-9.00

-11.00

-13.00

-15.00

MIT-4 - Unit shaft friction - Tension - SAND+CLAY [kPa]

0 50 100 150 200 250 300 350 400

-- A I+ FurI C - I ~ -- W

Figure 7.2 - MIT-4 - Tension - Axial capacity distribution

59

1.00

-1.00

-3.00

-5.00

-7.00

EC0

U.1

-9.00

-11.00

-13.00

-15.00

7.5.2. Compression loading

The pile load test under compression for pile MIT-4 is presented in Figure 7.3, the predicted axial

capacities are also included. The behavior of the load-displacement curve is ductile, with small elastic

deformation (e.g. 4 mm after the first unloading cycle). The yielding load is reached at an approximate

displacement at the pile head of 8 = 25 mm (Figure 7.3). This displacement equates to 8/D = 4.1%, which

is considered low given that the methods are based on a ratio of 6/D = 10%. Nevertheless, this state is not

conclusive; based on the deformations read during the load test, it can be argued, that the maximum

displacement was not reached, due to hardening of the load-deformation response. This argument could

validate the results of the UWA-05 and the ICP-05 method that slightly over predict the pile capacity

(Figure 7.3).

The variation of the prediction is higher for the compression mode than in tension, because: i) the API-00

method considers that the calculated unit shaft friction in tension and compression is equal, on the other

hand the CPT based methods allow Ts in compression to be higher than -, tension; ii) Plug formation was

assumed, in other words, no analysis of plug formation was performed in addition to that incorporated in

each method. The UWA-05 and the ICP-05 include formulations that analyzes this problematic condition,

i.e. if the plug is formed, and if so, if it is full or partial.

MIT-4 - Pile Load Test Compression (ID 86-01) Load (kN)

0 500 1000 1500 2000 2500 3000 3500 40000

5-e

E 10

E --- Load test :2737 kN-API :3688 kN

15 -0- FUGRO :3891 kN - - - -

- -ICP :3059 kNS -- NG :2745 kN

20 -0-UWA :2883 kN

25

Figure 7.3 - MIT 4 - Compression load test and predicted axial capacity

60

From the analysis of Figure 7.3 and 7.4 further conclusions can be made:

* The API-00 over estimates the resistance of the unit shaft friction for the upper sand layers

(similar to the tension mode), and consistently under estimates the shaft friction at depth, for the

lower sand layers (Figure 7.4b). The reasons for this behavior were discussed in the tension

section, and apply also to compression given that this method does not differentiate in modes of

loading.

* API-00 predicts an axial capacity for fully plugged mode of 3688 kN (Table 7-2), more than

double of the unplugged condition (1536 kN).

* API-00 follows the similar axial distribution, but it is offset by the tip resistance (Figure 7.4a).

* FUGRO-05 provides an upper bound prediction for compression, primarily due to over

estimating the contribution of the lower sand layers (El. -11.00 m to El. -13.00 m).and for tip

resistance (Figure 7.3a).

* NGI-05 provides the best prediction of load capacity in the compression mode, with a variation

ratio of QcaIc/Qtest= 1.003 (Table 7-2). Its estimation of the tip capacity seems to be consistent with

more refined methods that account for plug formation (UWA and ICP). The estimation of the

shaft resistance is low, thus its overall performance is conservative (Figure 7.3a).

* The ICP-05 and UWA-05 methods provide, again for compression, very close results. Their

computed variation ratios of Qcalc/Qtest differ by 5% (Table 7-2). The differences in predictions

can be traced to the tip bearing, 1455 kN and 1240 kN, respectively (Table 7-2).

. Both methods, ICP-05 and UWA-05, find that the pile is fully plugged. The ICP-05 method

calculates the tip resistance based on q = cone tip resistance averaged over a distance +1.5 D

from the pile tip, while the UWA-05 method calculates it using the Dutch technique

(section4.5.2). In pile MIT-4 the Dutch method provides lower average tip resistance.

* The ICP-05 limits the resistance at the tip, qbo.1, for the case of pile MIT-4 being plugged to 0.15*

q, (equation 4-18), while the UWA-5 method allows a higher stress of almost double this value.

Nevertheless, the UWA-05 method provides overall lower tip resistance due to lower average q,

obtain using the Dutch method.

* Note that despite the high variation in predictions, the variation at the pile tip (e.g. El. -13.00) is

almost identical as the variation of the total axial capacity at the top (Figure 7.4a).

61

MIT-4 - Axial load distribution - Compression - SAND+CLAY [kN]

0 500 1000 1500 20001.00

-1.00

-3.00

-5.00

-7.00

-9.00

-11.00

-13.00

-15.00

2500 3000 3500 4000

. I I . . I . . . ,

I I I

I I

-- A I-e ur ICP -- N l--U A

01.00

-1.00

-3.00

-5.00

-7.00

-9.00

-11.00

-13.00

-15.00

MIT-4 - Unit shaft friction distribution - Compression -SAND+CLAY [kPa]

100 200 300 400

Figure 7.4 - MIT-4 - Compression - Axial capacity distribution

62

500

EC04-

w

I I I

I I II I II I I

I I II I I

I I II I II I I II I II I II I I

I I I II I II II I

I I I

I I II I I II I I II I II I I II I I I

I I II I I I

-API ---Fugro -~-lCP -w--NGI -.-UWA


In section 6.2.2 the results of the site interpretation for pile MIT-i were presented. The interpretation

indicated the existence of cohesionless materials (28%) along the pile's embedded length and abundant

layers of fine grained materials. This interpretation disagreed with Caltrans' profile, which assumed

cohesionless materials for almost the entire profile (97%) as indicated in Figure 6.9 . Pile MIT-I was

nevertheless, considered into the axial capacity calculations included in the present chapter with the

purpose of providing further information on the piezocone's site investigation accuracy.

Pile MIT-1 is an open-ended steel pipe with a diameter of 0.41 m. The load test provided for this pile

included up-lift mode of loading only, and indicated a maximum load of 1068 kN (Figure 7.5).

Two predictions were performed for pile MIT-1, the first followed the interpreted profile of this study,

where clay dominates; the second included a more "subjective" approach in which if only slight

disagreement or indication of probable sands materials could be argued, that data point was assumed as

sand. The second scenario turned out to provide a lower bound to the predictions, with low average value

of axial capacity under tension (800 kN). Appendix E includes axial capacity prediction charts for the

second scenario (i.e. mostly sand profile).

Under the first scenario (interpreted - clay dominated), the axial capacities were over predicted, but in a

much closer range to the measured load test value. The ratios of predicted load to measured load included

in Table 7-3 for the design method confirm this statement (variation is less than 17%).

Load condition API-00 FUGRO-05 ICP-05 NGI-05 UWA-05 Load Test Averages(kN) (kN) (kN) (kN) (kN) (kN)

Tension

Sand-shaft 281 313 256 193 264 26123% 25% 21% 17% 22% 21%

Clay-shaft 953 953 953 953 953 95377% 75% 79% 83% 78% 79%


Qcalc/Qtest= 1.139 1.169 1.116 1.056 1.123 1.000 1.121

Table 7-3 - Pile MIT-1 - Pile axial capacity overview based on profile derived in Section 6.2.2

The fact that the second scenario (mostly sand profile) significantly under predicts the measured axial

capacity, substantiates the interpretation of the soil profile proposed in this thesis. Here, the higher pile

63

capacity of MIT-i is due to the existence of strong clay layers not identified in the original Caltrans

databse (Figure 6.9).

It is important to notice that the predicted axial capacity for the sand layers varies as much as 100 kN

among the design methods, this means a variation of as much as 50% for the lowest prediction. This

variation is considered high for a profile with an interpreted sand cover of only 28% of the pile's length.

The origins of this variation are explored next.


The load-displacement curve for the uplift test is presented in Figure 7.5, it includes the axial load

predictions from the five design methods, which over predict the capacity of pile MIT-1.

Figure 7.5 - MIT-1 - Tension load test and predicted axial capacity

Pile MIT-I experienced a very brittle behavior. After the 4' millimeter of displacement the pile "failed"

for a load of 1068 kN (Figure 7.5). Recalling that the estimated contribution of the clay layers is 953 kN

(Table 7.3), that means that the sand layers provide only around 115 kN of load capacity. Pile MIT-I has

a perimeter of 1.28 m, therefore the corresponding unit side friction for that load is 91 kN/m of pile

length. The sand layers in the profile are very thin, usually less than a 1 meter in width, but at the tip,

64

MIT-1 - Pile Load Test Uplift (ID 38-01) Load (kN)

0 200 400 600 800 1000 1200

0.00

5.00

10.00 Load test -1068 --IAP

- LFUGRO :1249 kNA - A ICP :1192 kN

X-- NGI :1128 kN1 15.00 --- UWA -: 1200kN - -

20.00-

25.00

there at two layers that could potentially provide the required unit shaft friction. These layers are located

at elevation -5.00 m and -6.00 m (Figure7.6). Their location seems to prove the brittle failure during the

pile test. After the clay layers have reached their capacity, the sand layers beneath the clay have to resist

the additional axial load. The failure occurs abruptly once the small contribution of the sand layers at the

tip is reached and all of the previous layers have reached their capacity i.e. no load distribution occurs.

Figure 7.6 provides the predicted shaft capacity under tension and the corresponding unit shaft friction.

The following observations can be made:

* FUGRO-05 provides the lowest shaft friction for loose sands (Elevation +6.50 m, +5.00 m, and 0)

* FUGRO-05 provides the highest shaft friction for dense sands, as can be seen at the increase in

load distribution at the pile tip (Elevation -6.50 in).

" API-00 provides the lowest shaft friction for dense sands, this supports the findings of the many

authors that on that basis developed the design methods being revised here.

" The limiting shaft frictions imposed by the API-00 method at each sand layer are not reached.

* UWA-05 and ICP-05 provide almost identical axial distribution curves and unit shaft friction, and

therefore total axial capacity.

" Plug formation is expected to happen in pile MIT-1. Weak materials are overlying a stiff layer at

the pile's tip. Weak and loose materials will collapse inside the pile and act as overburden on the

plug near the tip.

" The incremental filling ratio (IFR) for the UWA-05 method is 0.76, suggesting that the pile is

partially plugged.

" The NGI-05 method includes a limit on the minimum value on the calculated unit shaft friction, it

corresponds to 10% of the effective vertical stress. This limit controls for most of the pile's

length, from the pile's top to an elevation of -2.70 m where the first medium dense sands are

encountered.

* The location of the clay layers can be identified in the graphs, they occur where the unit shaft

frictions coincide.

" The calculated unit shaft friction among the five methods varies in proportion to the increase in

relative density. The upper loose sand layers vary in less than 10 kPa, while the lower denser

layers vary in as much as 150 kPa.

" In general, for pile MIT-1, the FUGRO-05 method provides the highest estimate of capacity, and

the API-00 the lowest.

65

MIT-I - Axial load distribution - Tension - SAND+CLAY [kNI

0 200 400 600 800 1000 1200

I I I I

I I I I

I I I I

I I I I

I I I I

I I I I

I I I I I I

I I I I

I I I I

I I I

I I I I I

I I I I

I I I I

I I I I

I I I I II I I I I

I I I I

I I I I I

I I I

I I I I

I I I II I

I I I I

I I I II I I I I I

I I I I

I I I

I I I I

I I I I I

I I I I I

I I I I

-API -a- Fugro -~--ICP -- u-- NGI -.---UWA

7.00

6.00

5.00

4.00

3.00

2.00

1.00

0.00

-1.00

-2.00

-3.00

-4.00

-5.00

-6.00

-7.00

MIT-1 - Unit shaft friction - Tension - SAND+CLAY [kPa]

0 50 100 150 200 250 300

-=

-on

-API -Fugro -ICP NGI - UWA


66

7.00

6.00

5.00

4.00

3.00

2.00

- 1.00

0 0.00

w -1.00

-2.00

-3.00

-4.00

-5.00

-6.00

-7.00


Pile MIT-5 is a square concrete pile 10.35 m long (embedment) and 0.36 m wide (Figure 6.10). The

distribution of main soil groups in the pile's embedded length is presented in Table 7-4. Pile MIT-5 offers

the most interesting pile from the point of view of the scope of this thesis, since the profile is dominated

by sand layers (81%).

Layer Thickness (%)(M)

Sand 8.35 81%Clay 2.00 19%

Pile embedment: 10.35 100%

Table 7-4 - MIT-5 - Coverage of pile embedment per layer

The pipe-soil elevations profile in Figure 6.10 summarizes the soil interpretation for pile MIT-5. In

general terms, three strata are found. An upper group of sand layers (El. +8.54 m to El.+4.53 in), a mixed

layer system of sand and clays between El.+4.53 m to El.+1.38 m, and a lower group of sand layers with

increasing relative density (Dr) with depth, from El.+1.38 m and to the pile's tip. For further detail on the

site interpretation please refer to Appendix B. The results of the calculated axial capacity predictions for

pile MIT-5 are shown in Table 7-5, its analysis follows in the next page.

Load condition API-00 FUGRO-05 ICP-05 NGI-05 UWA-05 Load Test AveragesTension_ (kN) (kN) (kN) (kN) (kN) (kN)

Tension

Sand -shaft 530 610 562 546 554 56181% 83% 81% 81% 81% 81%

Clay - shaft 128 128 128 128 128 12819% 17% 19% 19% 19% 19%


Qcalc/Qtest = 1.028 1.159 1.080 1.055 1.068 1.000 1.078

Compression

Sand-shaft 530 895 678 710 739 71035% 53% 54% 59% 58% 52%

Clay - shaft 128 128 128 128 128 1288% 8% 10% 11% 10% 9%

Tip bearing 863 664 439 373 403 54858% 39% 35% 31% 32% 39%


QcalcQtest = 1.302 1.469 1.084 1.054 1.106 1.000 1.203

Table 7-5 - Pile MIT-5 - Pile axial capacity overview

67

The axial capacity predictions of pile MIT-5 under tension using the four CPT-based methods, are in

good agreement with the quoted load test value capacity reported by Caltrans (614 kN, Table 7-5). The

average variation of the design methods

is 1.078 (i.e. 7.8%, Table 7-5).

Note that in tension, the load distribution between the sand and clay layers follows the same proportion as

the soil distribution coverage around the pile, i.e. the sand layers cover 81% of pile's length (Table 7-4)

and in average for the design methods they provide 81% of the capacity (Table 7-5). This coincidence

suggest that the shaft resistance is uniform in the pile, but later it will be shown that this is not the case.

In compression, there is an increase in the variation of the ratio Qcaic/Qtest = 1.203 compared to the tension

case. All of the proposed design methods over predict the pile capacity. NGI-05 provides the lowest

prediction, and thus closest to the measured value, on the other hand the FUGRO-05 provides the highest

prediction;, almost 50% higher than the measured load capacity (Table 7-5).

ICP-05 and NGI-05 present the most consistent prediction in tension and compression, for both cases,

their ratio of variation Qcaic/Qtest is identical, the very small difference, less than 0.1%, is well below the

accuracy that should be expected in any geotechnical calculation. UWA-05 presents a small variation in

both loading modes, however this variation is less than 4%, and therefore well within the "experimental

accuracy" of this analysis.

On the other hand, the FUGRO-05 and API-00 provide large variation between the tension and

compression modes, with ratios that differ 31% and 27% respectively (Table 7.5).

In the next sections, each mode of loading will be analyzed in more detail and in combination with the

output graphs from the spreadsheet program (Section 7.4).


The pile-displacement results for Pile MIT-5 are shown in Figure 7.7. The curve includes 3 loading cycles

that reached a maximum load of 614 kN at a displacement of approximately 5 = 24 mm (Figure 7.7). The

curve exhibits a very ductile behavior under tension loading (Figure 7.7). The yielding point is not well

defined, and in the opinion of the author the load test should have proceeded further to allow better

identification of the capacity. In Figure 7.7, at a displacement of 20 mm a load reading close to 600 kN is

68

reached, the next data point occurs at a displacement of 22 mm and a load of 614 kN (Figure 7.7), after

this maximum the load is released an the unloading cycle begins. It can be argued, that additional load

imposed at the pile at a deformation of 22 mm could further increase the load, and repeat the observed

behavior at the previous loading cycle, e.g. at displacement 10 mm. At that location, and after unloading,

the pile was able to pick-up more load (Figure 7.7).

MIT-5 - Pile Load Test Tension (ID 87-02) Load (kN)

0 100 200 300 400 500 600 700 8000

5

0E 10

-V- Load test :614kN-- API 632 kN15 - - FUGRO :712 kN

A ICP :664 kNX NGI :648 kN

-4-UWA :656 kN20

25

Figure 7.7 - MIT-5 - Tension load test and predicted axial capacity

Details on the load distribution of the design methods are presented in Figure 7.8:

" Figure 7.8b presents the unit shaft friction profile for pile MIT-5. It can be noted that the stiff

sand layer at the pile tip provides a large contribution to the load capacity. Below El. 0 m, the unit

shaft friction increase steadily to average values of 100 to 200 kPa. In the other graph, in Figure

7.8a, it can be noted that the lower dense sand layer provides almost 60% of the total load

capacity of the pile, i.e. 400 kN.

" From elevation El.+2.00 m to El.+8.54 m the unit shaft friction presents a uniform decrease of

resistance that equates to a load of approximately 300 kN.

69

* The contribution of the interlayer system of sand and clay between El.+ 4.53 and El. +1.38 to the

total axial capacity indicates a linear increase (Figure 7.8a), the corresponding average unit shaft

resistance is uniform close to a value of 50 kPa (Figure 7.8b).

" API-00 provides a lowest value on all the predictions. The contribution of the stiff base sand layer

is limited by the guidelines of this method (Figure 7.8b)

* FUGRO-05 provides the highest estimate of tensile capacity. At the pile tip, the method over -

stimates the contribution of the stiff sand layer. The source of this over prediction can be

explained by the fact that the FUGRO-05 method does not include friction fatigue in a zone of 2

diameters from the tip. Given that pile MIT-5 is founded into a stiff sand layer, which is not

corrected by FUGRO-05 the resulting unit shaft friction values are high. FUGRO-05 was

developed from load tests performed in long piles, where the contribution of the small

uncorrected area at the tip doesn't make much difference, but for onshore short piles, this area

greatly influences the results.

" UWA-05, ICP-05 and NGI-05 follow a similar load distribution, from pile tip to top. These

methods experience the larges difference in the interlayer system previously discussed, e.g. at

El.+ 4.00.

" Overall, this pile is a good confirmation of the accuracy of most of the design methods for

application in onshore short piles.

70

MIT-5 - Axial load distribution - Tension - SAND+CLAY [kN]

0 100 200 300 400 500 600 700 800

I II I

- A I - I ur + I - I G -+ W

- I

8.00

6.00

4.00

2.00

0.00

-2.00

MIT-5 - Unit shaft friction distribution - Tension - SAND+CLAY[kPa]

0 50 100 150 200 250 300 350 400

-- API -m--Fugro - -lCP --- NGI -+- UWA

I I II I

I I

I I II I


71

8.00

6.00

4.00C.2U)

2.00

0.00

-2.00

7.7.2. Compression loading

Pile MIT-5 is closed-ended, this provides a great opportunity to establish the applicability of the design

methods in their "pure" tip bearing form. (i.e. without any misinterpretations regarding plug formation)

The compression load-displacement test for pile MIT-5 is shown in Figure 7.9 and includes three loading

cycles up to a load of 1148 kN and a displacement of 23 mm. The load curve indicates a brittle behavior,

common for piles bearing on stiff layers at the tip (e.g. sand layer at El. -1.00, Figure 6.9).

The yielding load is reached at an approximate displacement of the pile head of 6 = 15 mm (Figure 7.9).

This displacement equates to 5/D = 4.2%, which is considered low given that the methods are based on a

ratio of 8/D = 10%. This is especially true for the UWA-05, FUGRO-05 and API-00 methods that specify

this limit at the pile tip, which is expected to be less that the measured values at the top. It appears, that

for on-shore piles, this definition of tip bearing resistance corresponding to 8/D = 10% should be revised.

The brittle behavior of the load test, can be explained by comparing the pile-soil profile of Figure 6.9 and

the calculated unit shaft resistance included in Figure 7.10. The pile tip is anticipated to be located at

EL.-1.83 m, just at boundary of the stiff sand layer and a softer material that follows. The CPT sounding

ends at the pile tip and therefore this underlying layer cannot be identified, nevertheless, the Caltrans

profile included in Figure 6.9, classifies that layer as a medium dense sand layer (N=12). As the pile is

loaded, from head to tip, the maximum capacity of all the soil layers is reached (Figure 7.1Gb), the

remaining load is taken as tip resistance by the stiff sand layer (El. -0.12 m to El. -1.62 in). When that

layer reaches its capacity no further distribution of load is possible, and the pile "fails".

The ICP-05, NGI-05 and UWA-05 provide the best predictions in compression, with a variation of less

than 10% to the measured values (Table 7-2). Out of these methods the NGI-05 has the best accuracy for

pile MIT-5. The similarity in their load distribution profile can be noted in Figure 7.1Oa.

The API-00 method performs in exactly the same manner as in the previously described piles. At the top

layers, it tends to predict a higher unit shaft friction resistance (trf). At the lower stiff layers, the design

method restricts its Trf calculated capacity. These limits are smaller than the available capacity that the stiff

sand layers can provide (Figure 7.1Gb).

72

In pile MIT-5, API-00 fails to incorporate into its prediction the influence of the weak layer of sand under

the stiff bearing layer (El. -0.12, Figure 6.9). Its formulation for calculating the bearing pile capacity is

based on effective stresses at the pile tip location, this number is then modified by a bearing capacity

factor to obtain the unit end bearing (Equation 4-2). This approach excludes any averaging technique and

can over estimate the local bearing capacity of a pile resting just above the boundary of a stiff material

overlying a weaker one, as is the case of pile MIT-5 (El. -1.62, Figure 6.9). In this case the bearing factor

is expected to be greatly influenced by the weaker layer and therefore it should be reduced accordingly,

an averaging technique should be recommended.

In pile MIT-5, FUGRO-05 confirms its past performance; it provides an upper bound prediction to the

design methods. The origins of this over estimation was described in the other pile's description. In

summary, FUGRO-05 was developed from load tests performed on open-ended large scale piles. Its

interpolation to small onshore piles fails to accurately predict their behavior at the tip, especially when

there is a presence of a stiff bearing layer.

MIT-5 - Pile Load Test Compression (ID 87-01) Load (kN)

0 500 1000 15000

5

EE

10 -+- Load test :1148kNE 0

-- API :1495 kN- -6- FUGRO :1661 kN

Mn- ICP :1218 kN

-V- NGI :1184 kNS15 4---UWA 1244 kN

0

25 7s

Figure 7.9 - MIT-S - Compression load test and predicted axial capacity

73

MIT-5 - Axial load distribution - Compression - SAND+CLAY [kN]

0 250 500 750 1000 1250 1500 1750

8.00

-- API

-- Fugro6.00-

---ICP

-- NGI

- UWA

E 4.00-

I I

2.00 -

-2.00-

MIT-5 - Unit shaft friction distribution - Compression -SAND+CLAY [kPa]

8.00

6.00

4.00

2.00

0.00

-2.00

0 100 200 300 400 500 600 700

I I * I I I

-API

-'-Fugro

ICP

-- NGI

-- UWA

II I I

Figure 7.10 - MIT-5 - Compression - Axial capacity distribution

74

8. SUMMARY OF REVIEW OF CPT DESIGN METHODS

This Chapter provides a summary of the pile axial capacity predictions, presented in detail in Chapter 7;

and a review of the considerations and limitations that can be drawn for each of the design methods based

on the analysis performed in this thesis for piles.

Two piles were considered for analysis from the results of the axial capacity predictions, namely: MIT-4

and MIT-5. Pile MIT-1 contained mostly clays, and therefore its calculated capacities, included in section

7.6., were used to confirm the CPT based site investigation, and to provide information on the

performance of the design methods. Nevertheless, being the scope of this thesis the review of pile design

methods in sand, its results cannot be included in the present summary

8.1. Tension loading

Table 8-1 presents the ratios of calculated pile capacity to measured pile capacity (Qcac/Qmeasured) for pile

MIT-4 and MIT-5 under tension. The API design method, based on an earth pressure approach, performs

well, within a variation of 5% of the measured values for the short on-shore piles revised here. The off-

shore design methods provide a greater variation, with a tendency toward the unconservative side (i.e.

Qcalc/Qmeasured >1). The UWA-05, ICP-05 vary in a range from -5% to 10% (Table 8-1), but are considered

acceptable given the Factors of Safety typically used for ultimate capacity of pile foundations

(e.g. F.S.= 2.0). NGI-05 provides great conservatism at Qcac/Qmeasured <0.8. FUGRO-05 has a greater

variation, next to 20%.

Summary of Tension Loading

1.20

1.10 ---- --- ----- ------- - --- - - ------

1.00

CY 0.90 ------ ----- ----- ------- ----------- - - -

0.80 ------------ K------------- ---------------

CY 0.704 5 Pile

*API-0 0 FUGRO-05 A ICP-05 )KNGI-05 0UWA-05

Table 8-1 - Summary of prediction of total pile capacity in Tension

75

The recognized advantages that the CPT design methods have on the API approach in the off-shore arena

(Lehane et al. 2005a), are not fully utilized for smaller scale, onshore piles.

For example, the API method includes limiting values on the unit shaft friction that tend to over estimate

the effect of the friction fatigue due to driving, and therefore underestimate the contribution of shaft

resistance for many soil layers in off-shore piles. The criterion for assigning this limiting value is based

on the effective stresses (i.e. depth of point of interest). For on-shore piles with lengths shorter than 10-20

m, the imposed limitation is only applicable to the lower soil layers. The advantage that the CPT methods

can provide in tension loading is reduced to a smaller area in the on-shore piles.

8.2. Compression loading

In compression, three of the CPT design methods - NGI-05, ICP-05, and UWA-05 - provide the best

agreement of calculated to measured load, for both, open-ended piles (MIT-4), and closed-ended piles

(MIT-5) as indicated in Table 8-2.

The API-00 and the FUGRO-05 method provide unconservative results, being FUGRO the design

method in compression with the highest probability of failure, QcaIc/Qmeasured>1.40, Table 8-2.

Summary of Compression Loading

1.50

1.40 -- ---- -------- -----------------

1.30 ---------- ----------------------- --------

O1 .2 0 -- - - - - - - - - - - - - - - - - - - - - - - -Eo 1.10 ----- A------------------------ -

1.10 ---- ----- t------- - - ----

1.000.90

4 5 Pile

*API-00 OFUGRO-05 ,ICP-05 )KNGI-05 OUWA-05

Table 8-2 - Summary of prediction of total pile capacity in Compression

It was noticed, for the analyzed piles, that the failure load during the compression load tests was achieved

for displacements significantly lower less than 8/D=10%, which is the design criteria of the CPT design

methods. The quality and extent of the load tests, did not allow concluding whether the load test was

terminated before failure was achieved, or that the CPT design methods need to be calibrated for smaller

76

displacement/diameter ratios. Definition of this disagreement will require more detailed load-

displacement curves.

8.3. API-00

The main advantages of the API design method, is that it is a simple method, and that it has been applied

in many offshore areas since 1969 (Chow 2005). This historic record proves its quoted conservatism

(Lehane et al. 2005a), and explains the difficulty of adopting a different standard.

In this study it was found that the API-00 provides reliable total axial pile capacities in TENSION. Its

under prediction of the unit shaft resistance of sand layers at depth, is canceled out by over predicting the

contribution of the shallower sand layers. It was noted that API-00 is more conservative with increasing

relative density, i.e. the influence of the limiting shaft friction is greater, compared to the resistance of a

dense sand near the pile tip (e.g. pile MIT-5).

In COMPRESSION, API-00 proves to be very unconservative for open-ended and closed-ended piles.

For the case of open-ended piles, API-00 fails to predict the formation of soil plug, and therefore further

analysis is required by the used to determine if the unit tip bearing is applied to the pile's annulus, the full

plug area, or if the plug is controlled by the coring resistance against the pile's inner walls. For closed-

ended piles, the pile tip bearing is determined locally at the pile tip, with disregard to the surrounding

layers. This can lead to high probability of failure, if the pile is founded on thin, but stiff sand, underlined

by a weak material layer (e.g. MIT-5).

8.4. FUGRO-05

In the review undertaken in this thesis, the FUGRO-05 design method provided the worst performance,

overestimating the measured capacity by approximately 45% (Table 8-1, and Table 8-2). This method

was developed from empirical results form the Euripides testing program in large scale piles (Zuidberg et

al. 1996), and therefore the limiting values included into its formulations emulate the testing conditions

and dimensions of those load tests. In addition to that, the FUGRO-05 method does not properly deal with

the possibility of a stiff sand layer occurring right at the pile tip (MIT-5 Figure 7.8 and Figure 7.10),

where no reduction of qc for friction fatigue is accounted for. Calibration of the FUGRO-05 for on-shore

piles, is nevertheless possible by adjusting its parameters using a larger database.

77

In COMPRESSION, the FUGRO-05, does not account for the formation of the soil plug. Further analysis

and input by the user is required.

One benefit of the method, is that its formulation and implementation is very simple. It only requires the

input of the pile dimensions and the measured cone tip resistance for the sand layers under consideration.

8.5. ICP-05

The ICP-05 design method was the pioneer of the CPT design methods. It traces its origins to 1996, it has

been used in 14 projects in North Sea (Chow, 2005), and therefore has a good confidence record. Its

formulation and calculation is more time consuming than the previous two methods. In addition to the

pile properties and the measured cone tip resistance, it requires these input variables: small strain shear

modulus (G0), and the constant volume interface friction angle (6,v). It provides two determine if a soil

plug formation should be considered. Pile tip resistance is provided by three equations, depending on the

plug formation, and pile geometry.

The ICP-05 was developed from a theoretical framework, but adjusted to a database of piles mostly

smaller than 0.9 m in diameter. In this regard, it suits the onshore pile dimensions better than other

methods developed for larger piles.

Its performance in tension and compression loading was satisfactory.

8.6. NGI-05

The NGI-05 design method performed conservatively for the loading modes explored in piles MIT-4 and

MIT-5.Its formulation is not related directly to the measured cone resistance, qc, but indirectly, because

this parameter is used to calculate the relative density of the sands layers. The calculated relative density

is then incorporated as a factor in the equation for predicting the axial capacity (Equation 4-20).

The calculation procedure of NGI-05 is simple for shaft resistance. Tip bearing requires soil plug

formation considerations, and therefore it is not user independent.

78

This method tends to under predict the unit shaft friction for medium to dense sands layers near the

surface (Figure 7.2 and Figure 7.4). A minimum value of unit shaft friction, tf = 10% the effective vertical

stress, is imposed for this method by equation 4-21. When the water table is located near the pile top, the

resulting unit shaft frictions are too low (Figure 7.2 and Figure 7.4 for pile MIT-4).

8.7. UWA-05

The UWA-05 design method performed well in this short study. In tension and in compression, open-

ended or closed-ended, its predictions varied less than 10% of the measured load-test values.

The calculation time and effort of this method is the largest of all the methods, but it has the advantage

that it is user independent. It was developed in the same theoretical framework as the ICP-05, and

therefore it follows the same logic and basically the same parameters. One difference is the evaluation of

the formation of a soil plug, which is included intrinsically in the method formulation. Its results in

compression, indicate that its approach is correct.

Its performance both in tension and compression are the most consistent of the design methods (Table 8-1

and Table 8-2) for the short on-shore pile considered in this thesis.

79

9. CONCLUSION

The execution of this thesis provided a great opportunity to review the applicability and accuracy of the

piezocone (CPT) measurements as a site investigation tool, and their use in predicting axial capacity of

driven piles in siliceous sands.

A detailed site investigation was carried out on a set of on six sites provided by Caltrans (Chapter 5).

Three of these sites have been examined in detail.

Two piles were used for comparing the four off-shore CPT based design methods for predicting axial pile

capacities and the API design criteria; these piles were: MIT-4 and MIT-5. The predictions were

calculated for short on-shore driven piles and compared against the measured load tests.

It was found that a the third test, MIT-1, was performed at a site with more clays than expected

(according to Caltrans database). A revised interpretation of the soil profile was used to compute the pile

capacity; it produced much better estimates of capacity than to those obtained using the original soil

profile.

and that was allegedly founded on sands, was effectively mostly covered by clays. These CPT site

interpretation results were confirmed by calculating the pile axial capacity and compare it to the load test.

The interpreted profile, that include mostly clays, provide a closer and better fit, than the site modeled

with sands only.

The results indicate that of the four off-shore design methods, three of them provide consistent and

conservative results. These methods are: ICP-05, NGI-05, and UWA-05. It was also found that for short

piles (e.g < 20 m) the API-00 design method provides similar results as to CPT-based design methods.

The CPT design methods incorporate a theoretical framework that improves the basic formulation of the

API-00 method. Further comparison of those methods against a larger database should improve their

applicability in both offshore and onshore locations.

This thesis concludes that design guidelines based on CPT measurements allow in depth analysis and

provide detailed information of the soil strata found in a given site. In this sense, they provide the

Geotechnical Engineer the tools to perform a sound and coherent foundation design.

80

REFERENCES

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API (2000), "RP 2A: Recommended Practice for Planning, Designing and Constructing Fixed OffshorePlatform." American Petroleum Institute, Washington D.C.

Aas, G., Lacasse, S., Tunne,T., Hoeg, K. (1986). "Use of in situ tests for foundation design on clay."Invited lecture ASCE Specialty Conference "in-situ'" Blacksburg

Baldi, G., Belloti, R., Ghionna, V., Jamiolkowski, M., Lo Pesti, D.F.C. (1989). "Modulus of sands fromCPT's and DMT's."12th International conference on soil mechanics and foundation engineering,Rio de Janeiro, pp. 165-170.

Baligh M.M., Ladd C.C. (1980). "Cone Penetration in Soil Profiling. Journal of the GeotechnicalEngineering Division." Proceedings of the American Society of Civil Engineers, Vol. 106, No.GT4, April, 1980, p.p. 447-461

Bustamante, M., Gianeselli, L. (1982). "Pile bearing capacity prediction by means of static penetrometerCPT." Proceedings of the 2nd European Symposium, Amsterdam, pp. 492-500.

Chow, F. (2005). "Time effects on piles and on their design methods. Presentation in the workshop: Axialcapacity of piles in siliceous sand." International Symposium on Frontiers in OffshoreGeotechnics, Perth, Australia (IS-FOG 2005)

Clausen, C.J.F., Aas, P.M., Karlsrud, K., (2005). "Bearing capacity of driven piles in sand, the NGIapproach". International Symposium on Frontiers in Offshore Geotechnics, Perth, Australia (IS-FOG 2005)

Helfrich, S.C., Wiltsie, E.A., Cox, W.R., Al Shafie, K.A. (1985). "Pile Load Tests in Dense Sand:Planning, Instrumentation, and Results." Proceedings, 17th Offshore Technology Conference,Houston, Tex., May 191985, OTC Paper 4847, Vol. 1, pp. 55-64.

Jamiolkowski, M.B., Lo Presti, D.F.C., Manasser, M. (2001). "Evaluation of relative density and shearstrength of sands from CPT and DMT." Soil Behavior and Soft Ground Construction,Cambridge, GSP No. 119, ASCE, pp. 201-238.

Jardine, F.M., Chow, F.C., Overy, R.F., Standing, J.R. (2005). "ICP design methods for driven piles insands and clays." Thomas Telford, London.

Kolk, H.J., Baaijens, A.E., Senders, M. (2005). "Design criteria for pipe piles in silica sands."International Symposium on Frontiers in Offshore Geotechnics, Perth, Australia (IS-FOG 2005)

Ladd, C.C. (1991). "Stability evaluation during staged construction." Terzaghi Lecture, ASCE Journal ofGeotechnical Engineering 117 (4): p.p. 540-615.

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Ladd, C.C., Foot, R. (1974). "New design procedure for stability of soft clays." J. of Geot.Eng. Div., ASCE, GT7, pp. 763-786.

Lehane, B.M, Chow, F.C., McCabe, B.A., Jardine, R.J. (2000). "Relationships between shaft capacity ofdriven piles and CPT end resistance." Proceedings of the Institution of Civil Engineers,Geeotechnical Engineering, Vol. 143, No. 2, p.p. 93-101

Lehane, B.M, Randolph, M.F. (2002). "Evaluation of a Minimum Base Resistance for Driven Pipe Pilesin Siliceous Sand." ASCE Journal of Geotechnical and Geoenvironmental Engineering, Vol. 128,No. 3

Lehane, B.M., Schneider, J.A., Xu, X. (2005a). "A Review of Design Methods for Offshore Driven Pilesfor Offshore Driven Piles in Siliceous Sand." GEO 05358, University of Western Australia,Perth.

Lehane, B.M., Schneider, J.A., Xu, X. (2005b). "CPT Based Design of Driven Piles in Sand for OffshoreStructures." GEO 05345, University of Western Australia, Perth.

Lehane, B.M., Schneider, J.A., Xu, X. (2005c) "The UWA-05 method for prediction of axial capacity ofdriven piles in sand." Proc. of the International Symposium on Frontiers in Offshore Geotechnics,Perth, Australia (IS-FOG 2005)

Mimura, M. (2003). "Characteristics of some Japanese natural sands - data from undisturbed frozensamples". Characterization and Engineering Properties of Natural Soils (2), Swets andZeitlinger, Lisse, p.p. 1149-1168.

Mayne, P.W. (2005). "Integrated Ground Behavior: In-Situ and Lab Tests. Deformations Characteristicsof Geomaterials." Proceedings IS Lyon, Taylor & Francis, London, Vol. 2, p.p. 155-177

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Randolph, M.F., Murphy, B.S. (1985). "Shaft capacity of driven piles in clay." Proc. 17th AnnualOffshore Technology Conference, Houston, 1, p.p. 371-378.

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Robertson, P.K., Campanella, R.G. (1988). "Guidelines for Use, Interpretation and Application of theCPT and CPTU." UBC, Soil Mechanics Series No. 105, Civil Eng. Dept., Vancouver, B.C., V6T1W5, Canada, 197 pp.

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Schmertman, J.H. (1976). "An Updated Correlation between Relative Density Dr and Fugro-TypeElectric Cone Bearing, qc". Contract Report DACW 39-76 M 6646 WES, Vicksburg, Miss.

Stevens, R.F., Al-Shafei, K.A. (1996). "The applicability of the Ras Tanajib Pile Capacity Method toLong Offshore piles." Proceedings Offshore Technology Conference, Houston, Texas, May 1996,OTC Paper 7974, Vol. 1, pp. 171-180.

Uesugi, M., Kishida, H. (1986). "Influential factors of friction between steel and dry sands". Soils andFoundations, Vol. 26, No. 2, pp. 33-46

Whittle, A.J. (2005). "Class Notes." Massachusetts Institute of Technology, MIT - 1.364 AdvancedGeotechnical Engineering, Chapter 5, p.p. 3-39

Zuidberg, H.M., Vergobbi, P. (1996). "EURIPIDES, load tests on large driven piles in dense silicasands." Proceedings, 28th Offshore Technology Conference, Houston, Tex., May 1996, OTCPaper 7977, Vol. 1, pp. 193-206.

83

APPENDICES

84

Appendix A - Site Investigation pile MIT-1

PILE MIT-1 - SITE INTERPRETATION RESULTS

Pile - ID # 1


CPT Top +10.67

Surface +8.54

Top of pile +7.32

Bottom offooting

+6.40

Water table +4.87

Elevations(m)

Steel pipe pileOpen ended0.41 m0.5" (1.27 cm)0.0157 m21.28 m16.86 kN

-t

CI-a.

Pile tip -6.71CPT tip -6.88

0.92

14.0313.11

-0.41

+10.67

+8.54

+6.40

+4.42

+2.13

+0.61

-2.13

-3.35

-4.57

-5.18-5.79

-7.01


Soil yso"I N Sutype [kNm3j [bpf ikPal

- 19 - -

Fill 18.8 - -

Sand 19.6 11 -

Sand

Sand

Sand

20.04 28

21

11

Sand 20.1 27 -

Clay

SandSand

Sand

5018

72

35.91

20.1

19.6

18.8

20.419.8

20.9

+10.67

+8.67

+7.82

+7.42

+6.37+6.17

+5.27

+4.62

Sand

J aydClay

Clay

Sand

Clay

34

36

30

35

+3.27 i t i i

+0.12

-1.08

-2.28

-3.23

-4.10

-4.98-5.38

-6.23-6.88


Soil * Dr Sutype (*I [% I kPa

Fill - - -

34 20

34 2090

90

60

150Clay

Sand

ClaySand

Clay

Clay

ClaySand i 44 1 80 -

38

40

40

42

45

60

60

70

175

125

90

175

85

. "w

MIT-1a MIT-lb

0 200 400 0 10,00011 -

10

9

8

7

6

5.

4

.2 2

] 1

0

-1

-2

-3

-4

-5

-6

-7

ovo

U0

11

10

9

8

7

6

5

4

3

2

1

0

-1

-2

-3

-4

-5

-6

-7

I--- s'vo - - - uO -svo, kPa I

20,000

I I

I I

I II I

I II II I

I I

I I

I II I

I II II I

I II II I

4i~IIIiII I

-

---Tip resistance (qc), kPa

MIT-Ic

0 200 400 600 800

I II I

I I II I I

-

-

MIT-i - Chart A - Vertical profile, CPT readings

86

11

10

9

8

7

6

5

4

3

2

1

0

-1

-2

-3

-4

-5

-6

-7

I II I I

I I

I I II I

I I II I

I II I

I I

I II I

I II I

I II I

I I

I I II I I

I II I

I II I I

I II I

I I II I

I II I

I I

I II II I

I II I I

- Sleeve friction (fs), kPa

MIT-Id

-100 0 100 200 300 40011

10

9

8I I

7I I I

I I II I I

6

5I I

4

3

2

1 - - - - I -

I I I

0

-1

-2II I I

-3

-5

-6

-7

-Pore pressure (u2) - - - uo, kPa

-

MIT-I MIT-I MIT-1

0 100 200 300 400 500 0.00 0.05 0.10 -0.10 0.15 0.40 0.65 0.90I I 1~ ~I I I I I I

I I I I I I I I II I I I I I I I II I I I I I I

I I I I I II I_I I I

I I I I II

I I I I I I II I I I I I I

I I I I I II I I I I I I

I I I I I I II I I I I I I II I I I I I II I I I I I I

I I I I I I I II I I I I II I I I I II I I I I I I I

I I I I I I I I II I I I I I I II I I I I I I I I

I I I I I I

11

10-

9.

8

7-

6-

5-

4

3-

I II II II I

I I I I I I I II I I I I I I

I I I I I I I I II I I I I I I I

I I I I I I I I II I I I I I I

I I I I I I I II I I I I I I I

- ~ -I------I I I I I I I

I I I I I I I II I I I I I II I I I I I

I I I I I I II I I I I I II I I I I I I

I I I I I

I I I I I I II I I I I I I I

I I I I I I I II I I I I

I I I I I II I I I I I II I I I I I I I I

I I I I I I I


I I I I I I I II I I I I I I

I I I I II I I II I I I I I I

I I I I I I I I I

I I I I I I I II I I I I


I I I I I I II I I I I I I I

I I I I I I I II I I I I I I I

I I I I I I II I I I I I II I I I I II I I I I I I I

- (qc-sv)/s'vo

11

10

9

8

7

6

5

4

3

2

0-

-1

-2

-3

-4-

-5-

-6-

-7.

11

10

9

8

7

-o

-6

-7

-fsqc

I I II I I II I II I I

I I I II I I I

I I II I I

I I II I

I I II I I I

I I II I

I I I II I I I

F~I. I III I II I I

I I I

I I I I

I I II I I

I I I II I I

I I II I

I II I I

I I II II I I I

--- u2qc

MIT-1 - Chart B, CPT normalized profiles

87

I I II I I II I I II I I,1

E

S2-

1

0-

-1

-2-

-3-

-41

-5

-6-

-71

.

I II I I

I I I I

I I I II I

I I I II I

I II I I II I I I

I I

I I I II I II I I II I I I

I II I II I II I I I

I II I I

I II I

- -~ I I II II I I II I I II I I I

I I II I I II I II I I I

I I- -.----I. I I I

I I II I I II I I II I I I

6

5

MIT-1 - Correlation depth vs qc [kPa] forvarious ' - (Mayne 2003)

0 10,000 20,000 30,000 40,000 50,000 60,00011

10

9

8

7

6

5

4

3

2

1

0

-1

-2

I I II I I

I I I

I I

I II I I

I I

I I

42 44 46 = 4' [0] 40% 50% 60% 70% 80% 90%

- 30 - 32 - - - 34 -- 36- 38 40 -'42 44

46 - 48 - qc, kPa

0.1 - -0.2 - 0.3 -m--0.40.5 - 0.6 '-0.7 0.8

-- 0.9 1 qc,kPa

MIT-1 - Chart C . Friction angle and Relative density graphs for cohesionless materials

88

11

10

9

8

7

6

5

4

3

2

1

0

-1

-2

-3

-4

-5

-6

-7

E

0

CIO

ED

MIT-1 - Correlation z vs q, [kPa] for various Dr(Jamiolkowski 2003)

0 10,000 20,000 30,000 40,000 50,000

Axx

-3

-4

-5

-6

-73436 38 40 100% = D,

MIT-1

11

10

9

8

7

6

5

4

3

2

1

0

-1

-2

-3

-4

-5

-6

-7

MIT-1 -suDSS

0 100 200 300 400

- I

- I

I-I

-I v Ivo

' 'I ' I'

o 100 200 300I I I I I II I I I I I I II I I I I I II I I I I I I II I I I I I


I I I I I I II I I I I I I II I I I

I I I I I II I I I I

I I I I I I

I I I I I I I II I I

I I

I I I I I I I II I I


I I I I I I I

I I I I I I II I I I I I II I I I I

11

10

9

8

7

6

5

4

3

2

1

0

-1

-2

-3

-4

-5

-6

-7

I I II I I I II I I I I I

I I I I I II I I I II I

I I I I II I I

I I I I I I I I I

:7 I I :I I I : :I.1

MIT-1 - Nk

0 10 20 3011

10

9-

8-

7.

6-

5

4-

3

2-

1

0

-1

-2

-3

-4

-5

-6

-7.

MIT-1 - OCR

0 5 10 15

I I II I

I I II I II I I

I II I

I I I

I I I

I I

I I

I I II I I

I I II I

I I

I I I

I I II II I

I I II I

I I

I I

I II I

I I I

11

10

9

8

7

6

5

4

3

2

1

0

-1

-2

-3

-4

-5

-6

-7 -

I- - - u0 - s'vo ----- svo - Su Interpreted, kPa -- Cone Resistance Factor

MIT-1 - Chart D, (Undrained strength and stress history of clay layers)

89

I II I

I I I II I I I I I

I I I I I I II I I I I

I I I I I I I II I I I I I II I I I I

I I I I I II I I I I II I I I I

I I

C

0

w

-- OCR

I I II I

I II I

I I I

I II I

I I I

I I

I I

I I

I I

I I

I I II I II I II II I I

I I

I I II I II I II I I

I I

k 0

1000 1. I''''I

7t:-9-N4

1-1

(D

0

0

0*

G)

0.1

100

10

11

Friction Ratio (

10

1. Sensitive Fine Grained2.3.4.

Organic Soils -PeatsClays - Clay to silty claySilt mixtures - Clayey silt to silty clay

5. Sand mixtures - Silty sand to sandy silt6. Sands - Clean sand to silty sand7. Gravelly sand to sand8. Very stiff sand to clayey* sand9. Very stiff fine grained*

*Heavily overconsolidated or cemented

1


A~ X

6 X

0 10 100

F-- fs/(qc-svo) -- (qc-sv)/s'vo

MIT-1 - Chart E - Soil Classification (Robertson and Campanella, 1988)

90

0

1000 10000

0

U

11

10

9

8

7

6

5

4

3

2

1

0

-1

-2

-3

-4

-5

-6

-7

84

I I I IfIi l

I i I l l , i i l i l i I l i I I I f i l l I I I I I I

I r M O I- I I I I I Ili i IiI i I I i I

Appendix B - Site Investigation pile MIT-5

Pile MIT-5 - SITE INTERPRETATION RESULTS

Pile - ID # 5


CPT Top +10.98Surface +10.67

Top of pileBottom offooting

Square concrete pileClosed ended0.36 m

0.0993 m21.12 m26.38 kN

+9.45

+8.54

Water table +6.40

-0

Elevations(in)

CPT tipPile tip

0

-1.62-1.83


Soil y-oi Ntype [kN/m3] [bpfq

0.91

0.36

10.35

+10.67

+8.54

+7.62

+6.71

+5.49

+4.57

+3.96

18.80

19.8

19.8

20.1

19.8

19.8

20.1

Sand

SandSandSandSand 20.4_[ 34

Sand

+2.44 1 i

+0.91

+0.30

-0.30-0.91

-1.52...

-3.05

20.4

20.4

20.4

20.4

20.4

20

28

35

56

12


Soil ' Dr Sutype 10 [%] [kPa]

+10.98

Fill - - -

+8.54Sand 38 45 -

+7.73________

Sand 40 55 -

+5.58

Sand 38 40 -+4.5 4. -' - -

+3.83 Sand 36 30 -

+3.13 Clay - - 110

+2.73 Sand 38 45 -+2.38 - -+2.18 Sand 36 30 -

+1.38 Clay - - 100

Sand 38 40 -

+0.28 Sand 40 60 -

Sand 41 65 -

Sand 41 70 -

-1.62

Pile-soil elevations profile

91

- 19

-8

8

14

9

7

12

Fill

Sand

Sand

Sand

Sand

Sand

Sand

MIT-5

0 100 200 30011 .

10

9 -

8

7-

6-

5I

4 I

3

0

-1 '

- I

uo I-3

- - -uo --- s'vo - -so

MIT-5

0 10,000 20,000 30,000

I. . ,

I

I

I I II I I

I I I

I

MIT-5

0 200 400

10 I

8

7

6

9

4 -I

3

2

1

-2

I31

600 800

-Tip resistance (qc), kPa --- Sleeve friction (fs), kPa

MIT-5 - Chart A - Vertical profile, CPT readings

MIT-5

-100 -50 0

I 9 II II II I

9 I

I II II II II II I

I II II II I

I II I I

I I

I I II I

I I

I II

I I

I I I

I I

I II I III II I

I II II I I

I I I

I I

I I II I II I II I I

I-- Pore pressure (u2) - - - uO, kPa

50 100

92

MIT-5

0 100 200 300

MIT-5

0.000 0.020 0.040 0.060 0.080

MIT-5

-0.040 -0.020 0.000 0.020

I I II I II I I I I

I I I IC I I I

___ I- I I I II I II I I I

I I II I I

I I II I I II I I II I I I II I I

I I II I I II I I I

I I II I I

I I I I II I I

I I II I I I

I I I II I I I II I I I II I I I

I I II I I

I I II I I I

I I II I I

I I I II I I I

I I I I

I I I I

I I II I I I

I II I I I II I I I I

I I I II I I I I

I II I I I I

I I I II I I II I I I I

I I I II I I I II I I I

I I I II I I

I I II I I I II I I I

I I I

I I II I I II I I

I I I II II I I I

I I I II I I I

I I I I II I I C I

' ' I ' I'

10

7

5

4-

3-

2-

0

-2-

-3-

I I

I I

I II I

I I II I I

I I

I I I

I I

I I II I II I

I I II I II II I

I II I I

I II I

I I 1I I

I I II I I

I II I

I I I

I I I

I II I I

I I

I II I

I II II I II I I

I II I

I II I

I II I

I I

I II I I

-*- fs/qc

MIT-5 - Chart B, CPT normalized profiles

11

10-

9-

8

7

6

5

3

2

1

0

-1

-2

-3

11

10

9

8

7

6

5

4

3

2

0

-1

-2

-3

(qc-sv)/s'vo -+-u2/qc

93

-

8

1

MIT-5 - Correlation depth vs qc [kPa] for various(Mayne 2003)

10,000 20,000 30,000 40,000

MIT-5 - Correlation depth vs q, [kPa] for various Dr(Jamiolkowski 2003)

0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 40,000

1-I.1fEli 3k1 x!l

I ---

.15-I.a--~--J~I UlZLtiZ][IflV-kL

. K . U

-u

9

8

7

6

5

4

3

2

1

0

-1

-2

F Iti -

34 36 38 40 42

11-

10

9

8

7-

E

0D

6

5

4

3

2

I

0

-1

-244 = [*]

I I II

L S I IL I

a d=.; I ILI I

A 1~1X~X-\-~--~Iii U~I

A IiUii U

___ lA~I~U i~ i IY

- -4-"

I1

ti

I-

'I

I II II I

I

U II

:I- -

30% 40% 50% 60% 70%

I I I

80% 90% = Dr

34 -"-36 -u-38 -- 40 -+-42 -44 -46 -+-48 -qc, kPa -0-0.1 0.2 -"--0.3 -- 0.4 -- 0.5 - -0.6 - 0.7 - 0.8 - 0.9 -- 1 -.- qc,kPa

MIT-5 - Chart C . Friction angle and Relative density graphs for cohesionless materials

94

011

10 II.

11C0

cc

Q)

EIE

I:

-- 30 -32

k X I X

==t A7

MIT-5

0 100 200 300 0

10

9 -

I I I I I I I I I I i

I I I I I I I I I I i

8

I I I I I I i i I I I I I I I I I I I

E | 1 1 i i I i6-

E_ 5-cc . I I I

3-

2-I l e i I I I I

0

-1

-2- UO VI

-3 -

- - - u0 --- s'vo -svo

11

10

9

8

7

6

5

4

3

2

1

0

-1

-2

-3

MIT-5 - Depth vs Su OSS

100 200

--- su Interpreted, kPa

I I I II I I I I

S I I I I I I IS I I I I I I I

I I I I I II I I I I II I I I I I I

I I I I I I II

I I I I I I

I I I I I

I I

0

MIT-5 -Depth vs Nk

10 20 30

I- Cone Resistance Factor I

MIT-5 - Chart D, (Undrained strength and stress history of clay layers)

95

11

10

9

8

7

6

5

4

3

2

1

0

-1

-2

-3

MIT-5 - Depth vs OCR

0 10 20 3011

10

9 -

8

7-

6

5

4

3-

2

1

0

-1

-2

3.

8 - -- - --

. Sensitive Fine Grained

. Organic Soils -Peats

. Clays - Clay to silty clay

. Silt mixtures - Clayey silt to silty clay

. Sand mixtures - Silty sand to sandy silt

. Sands - Clean sand to silty sand

. Gravelly sand to sand

. Very stiff sand to clayey* sand

. Very stiff fine grained**Heavily overconsolidated or cemented

1


MIT-5-Soil Classification (Robertson & Campanella 1988)

1000,

9

100

z 010

4.,

3

0.1 1 10Friction Ratio

E

0(U*

5

4

3

2

1

0

-1

-2

-30 10 100

--- fs/(qc-svo) -- (qc-sv)/s'vo

MIT-5 - Chart E - Soil Classification (Robertson and Campanella, 1988)

96

11

10

9

8

7

6

I T I I Iill11111 1II -1 1 T

11 1 1 1 | 1 111 1

I I I I 1 1 f i ll 11 1 1 1 1 1 1 1 1 1 1 1 1 1 1

I I I I I f ll1 , i i 1 I l II I I I I 1 I I I I I 1 1 I I I I I I

1111I

T 1 1111 I I

1 1=911 I I1 1 1 1 111 1 1 1 1 111 1 1 1 f1 111

t I I I I I t t 1 1 I I t I I I

1 ~ ~ ~ ~ ~ ~ ~ ~ --- -- --- 11 1T-r 1 l I i 1 i i 1 1 i 1

123456789

1000 10000

MIT-5 - Relative Density MIT-5 - Clay Shaft friction, kPa

... ~ ~ ~ ~ ~ ~ N 66... . . .X . , . . . .. .

(0.50) (0.30) (0.10) 0.10 0.30 0.50 0.70 0.90 1.10 1.30 0

I--- Jamiolkowsky - -NGI I

20 40 60 80 100 120

-+- qc/50 --- Su

MIT-5 - Chart F - Comparison of relative density and undrained shear strength

97

8.00

6.00

C0

u

4.00

2.00

0.00

-2.00

I

8.00 I

I . I

6.00

Appendix C - Pile-soil profile for pile MIT-3

Pile - ID # 3


Top of pileCPT Elevation.Surface elevation

Bottom of footing

Steel HP 10x57 pileOpen ended0.25 m

0.0108 m21.03 m12.90 kN

+110.52

+110.06

+108.69

0)0)CCU

(UCU

CI-a-0

15.55Elevations(mn)

CPT tip

Water table

Pile tip

+98.91

+97.56

+94.97

1.83

13.72

0.25 -

+110.06

+108.69

+107.93

+107.32

+106.10

+105.18

+104.57

+103.35

+102.13

+100.91

+100.00

+98.48

+96.95

+94.82


Soil ysoil N Sutype [kN/m3] [bpfj [kPa]

Fill 18.06 - -

Sand 19.6 12 -

Sand 20.4 75 -

Sand 19.6 9 -

Sand 19.6 12 -

Sand 20.1 30 -

Sand 19.9 20 -

Sand 19.08 15 -

Sand 20.06 96 -

Sand 20.1 36 -

Sand 20.1 20 -

Sand 20.1 28 -

Sand 20.3 34 -

98

Appendix D - Pile-soil profile for pile MIT-6

Pile - ID # 6

Type of pile: Steel HEnd condition: Open eDiameter: 0.36 mThickness: -Base area of pile: 0.0168Perimeter: 1.45 mWeight of pile: 22.01 k

Surface elevation +27.13CPT Elevation +26.83

Top of pileBottom of footing

+25.30

+24.69

Water table +19.97

Elevations(m)

P 14x89 pilended

m2

N

1.84

0.60

C

n

+13.48 -L-

+8.23

0.36 -

16.47

+27.13

+24.69

+21.65

+19.82

+17.99

+15.85

+15.24

+14.02

+12.20

+11.59

+10.98

+10.37

+9.76

+8.54

+7.01

+5.79

CALTRANS Soil ProfileSoil ysovl N Sutype [kN/m3] [bp] [kPa]

Fill 18.1 - -

Clay 17.3 0 95.77

Sand 20.1 30 -

Clay 18.1 0 119.71

Clay 17.3 0 95.77

Sand 20.1 30 -

Sand 20.4 59 -

Sandy 20.4 57 -gravel

Clay 18.1 0 119.71

20.4 50 -Sandy 20.4 65 -gravel

20.4 85 -

Gravel 20.4 94 -

Gravel 20.4 151 -

Gravel 20.4 96 -

CPT tip

Pile tip

99

MIT-1 - SCENARIO 2 PREDICTION - Axial load distribution - MIT-1 - SCENARIO 2 PREDICTION - Unit shaft friction - Tension -Tension - SAND+CLAY [kN] SAND+CLAY [kPa]

0 100 200 300 400 500 600 700 800 900 1000 0 50 100 150 200 250 3007.00 - 7.00

6.00- 6.00

5.00 5.00 -

4.00- 4.00-

3.00 3.00

2.00 2.00-

1.00 1.00 -

.2 0.00 0.00I

iii -1.00 - -1.00-

-2.00 -2.00

-3.00 - -3.00

-4.00- -4.00

-5.00- -5.00-

-6.00 -6.00-

-7.00. -7.00

-API - Fugro m ICP - - -x- - NGI -- UWA] -- API -- Fugro -&- ICP -,- NGI - -- UWA

Appendix E - MIT-1 - Axial capacity prediction - Second Scenario (Mostly sand profile)

100

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