Coffey G

eotechnics

TA

LL BU

ILDIN

GS

, DE

EP

FO

UN

DA

TIO

NS

; MID

DLE

EA

ST

E

XP

ER

IEN

CE

S

The 2009 Terzaghi Oration

Harry Poulos

Coffey G

eotechnics

OU

TLIN

E

D

esign Process for H

igh-Rise B

uildings

Em

irates Twin Tow

ers Project

Investigations

D

esign

Load tests

Tower foundation perform

ance

Burj D

ubai

Foundation design

Load tests

Foundation performance

G

old Coast B

uilding

Henry D

avid Thoreau

Walden (1854)

If you have built castles in the air,Your w

ork need not be lost;That is w

here they should be.N

ow put the foundations under them

.

FOU

ND

AT

ION

DE

SIG

N

PR

OC

ES

S

Site characterization

Geology

S

tratigraphy

Quantification of relevant geotechnical param

eters. B

ased on:

In-situ testing

Laboratory testing

Load testing

FOU

ND

AT

ION

DE

SIG

N

PR

OC

ES

S

Foundation Type & Layout.

Usually piles or piled raft

Based on:

Foundation loadings

Design criteria

C

onstruction issues

Material availability

FOU

ND

AT

ION

DE

SIG

N

PR

OC

ES

SD

esign Issues1.

Ultim

ate capacity2.

Settlem

ent3.

Differential settlem

ent & tilt

4.D

ynamic behaviour

5.E

arthquake response6.

Structural strength of foundation elem

ents7.

Durability

LOC

AT

ION

OF D

UB

AI

PR

OJE

CT

S

Em

irates Site -1996

SIT

E P

LAN

& B

OR

EH

OLE

S

INV

ES

TIG

AT

ION

PR

OG

RA

M

23 boreholes, up to about 80m

depth (maxim

um)

Trial pits

SP

T in upper layers

Undisturbed sam

pling

Water sam

ples

Perm

eability tests

Pressurem

eter tests

Vertical seism

ic shear wave profiling

U

niformity borehole testing

LAB

OR

AT

OR

Y T

ES

TIN

G

C

onventional laboratory & field tests

S

pecialized testing

Site uniform

ity testing (geophysical)

Cyclic triaxial testing

Effects of repetitive w

ind loading

Stress path triaxial testing

Deform

ation parameters

C

NS

testing

Ultim

ate shaft friction

Resonant colum

n testing

Dynam

ic shear modulus &

damping

GE

OT

EC

HN

ICA

L PR

OFILE

&

MO

DE

L FOR

EM

IRA

TE

S S

ITE

Eu MPa

E' MPa

fs kPafb M

Papu M

Pa

Silty Sand40

3018

0.20.1

Silty Sand125

10073

1.51.5

Calcareous Sandstone

700500

2002.3

2.3

Silty Sand125

100150

1.91.9

Calcisiltite

500400

4502.7

2.7

"90

80200

2.02.0

"700

600450

2.72.7

FOU

ND

AT

ION

TY

PE

S

Towers

Piled raft foundations

Podium

Piles, pile groups

LOA

D T

ES

T P

RO

GR

AM

B

elow each tow

er:

C

ompression test to 3000t, L=40m

, d=0.9m

Static tension test: L=25m

, d=0.6m or 0.7m

C

yclic tension test

Lateral load test

Class A

predictions made using assessed design

parameters

PR

ED

ICT

ION

ME

TH

OD

S

A

xial Response

N

on-Linear boundary element analysis

P

IES

program

Lateral Response

N

on-Linear boundary element analysis

E

RC

AP

program

Cyclic Tension Test

Non-Linear boundary elem

ent analysis

SC

AR

P program

TH

E E

MIR

AT

ES

PR

OJE

CT

, D

UB

AI

SE

TU

P FO

R C

OM

PR

ES

SIO

N

PILE

TE

ST

S(-2.00) (-0.50)(-1.50)(-5.00)(-10.0)(-16.0)(-20.0)(-25.0)(-30.0)(-36.0)(-40.0)

Working

platform

Unit1

-Silty

sand

Unit2

-C

alcareoussandstone

Unit4

-C

alcisiltite

Unit3

-Silty

sand

2030

1285

900

Ground

anchors

Reference

beams

Footprintoftheground

anchorsatthe

groundlevel

No.1

Extensom

eter

No.4

Straingauges

22N

osof

groundanchors

3000t LOA

D T

ES

T W

ITH

R

EA

CT

ION

AN

CH

OR

S

Emirates Project, D

ubai

LOA

D-S

ET

TLE

ME

NT

CU

RV

ES

FO

R P

ILE P

3(H)

010

2030

400

5000

10000

15000

20000

25000

30000

Applied Load (kN)

Settlement(m

m)

PredictedM

easured

PR

ED

ICT

ED

& M

EA

SU

RE

D

AX

IAL LO

AD

DIS

TR

IBU

TIO

NS

05000

1000015000

2000025000

30000

-40-38-36-34-32-30-28-26-24-22-20-18-16-14-12-10 -8 -6 -4 -2 0 2

Level DMD (m)

Measured

(15000kN

)M

easured(23000

kN)

Predicted

Load

(kN)

LOA

D-M

OV

EM

EN

T C

UR

VE

S

FOR

UP

LIFT T

ES

T

-35-30

-25-20

-15-10

-50

0 1000

2000

3000

4000

5000

6000

Applied Load (kN)

Measured

Predicted

Uplift(m

m)

ULT

IMA

TE

SH

AFT

FRIC

TIO

N

FRO

M T

ES

TS

0100

200300

400500

600700

50 40 30 20 10 0

Depth (m)

Ultim

ateSkin

FrictionkPa

Design

valuesD

educedfrom

P3(hotel)

piletest(com

pression)D

educedfrom

P1(hotel)

piletest(tension)

Deduced

fromP3

(office)pile

test(compression)

Deduced

fromP1

(office)pile

test(tension)

ME

AS

UR

ED

& P

RE

DIC

TE

D LA

TE

RA

L LO

AD

-DE

FLEC

TIO

N C

UR

VE

S

-10-5

05

1015

2025

Applied Load (kN)

0 25 50 75

100

125

150

175

200

Displacem

ent(mm

)

PredictedM

easuredM

easured

ME

AS

UR

ED

& P

RE

DIC

TE

D LA

TE

RA

L D

EFLE

CT

ION

vs DE

PT

H

-24

-22

-20

-18

-16

-14

-12

-10 -8 -6 -4 -2 0 2

Level DMD (m)

-1.00

2.04.0

6.08.0

10.012.0

Measured

Predicted(L

oad=150

kN)

Deflection

(mm

)

AS

SE

SS

ME

NT

OF

PR

ED

ICT

ION

S

Class A

predictions were in fair agreem

ent

Cyclic loading effects not w

ell-predicted

Assisted by:

Com

prehensive investigation data

Modern m

ethods of lab & field testing

S

traight-forward m

echanisms of behavior

EM

IRA

TE

S T

OW

ER

S-

FOU

ND

AT

ION

SY

ST

EM

S

1.5m thick raft

102 piles for office

91 piles for hotel

1.2 & 1.5 m

piles to 40-45 m

DE

SIG

N M

ET

HO

DO

LOG

Y

Limit State A

pproach

Ultim

ate Limit State:

S

tatic loads

Repetitive w

ind loads

Serviceability Lim

it State:

S

ettlements : m

ax. 150mm

A

ngular rotation: max. 1/350 long-term

TO

WE

R FO

UN

DA

TIO

N

AN

ALY

SE

S

GA

RP

program for piled rafts

U

ltimate Lim

it State:

U

sed both factored & unfactored pile capacities

M

any load combinations

S

erviceability Limit S

tate

Long-term settlem

ents -GA

RP

S

hort-term m

ovements (w

ind) D

EFP

IG for axial &

lateral stiffness of individual piles in group

Passed on to structural engineer for overall analysis

LOA

D C

OM

BIN

AT

ION

S

U

ltimate Lim

it State:

1.25G + 1.5Q

1.2G

+ 0.4Q + W

u

0.8G = W

u

S

erviceability Limit S

tate:

G + 0.4Q

Total of 18 load cases per tower

PILE

INT

ER

AC

TIO

N D

IAG

RA

M :

OFFIC

E T

OW

ER

DY

NA

MIC

FOU

ND

AT

ION

R

ES

PO

NS

E

Required for seism

ic & w

ind response

D

ynamic stiffness &

damping from

dynamic

pile group analysis via Gazetas approach

M

ATLA

B program

developed for evaluation

SE

ISM

IC E

FFEC

TS

Liquefaction:

Low

very low risk

Ground A

mplification of seism

ic motions:

C

ategory B assessed

modest am

plificationP

otential for Site S

ettlements:

A

ssessed to be low, 5-10m

m under design

earthquake, unlikely to cause excessive downdrag

loads on piles.

PR

ED

ICT

ED

SE

TT

LEM

EN

T

CO

NT

OU

RS

FOR

OFFIC

E T

OW

ER

05

1015

2025

3035

4045

500 5 10 15 20 25 30 35 40 45 50

y axis (m)

xaxis

(m)

100

110

110

110 120

120

120

120

130

130

130

110

110

55

100

Predicted Max.

Settlement =

134 m

m

PR

ED

ICT

ED

SE

TT

LEM

EN

T

CO

NT

OU

RS

FOR

HO

TE

L TO

WE

R

05

1015

2025

3035

4045

500 5 10 15 20 25 30 35 40 45 50

y axis (m)

xaxis

(m)

110

55

105

115

115

115

115

115

125

125

125

105

105105

105

105

Predicted Max.

Settlement =

138 m

m

TH

E E

MIR

AT

ES

PR

OJE

CT

, D

UB

AI

TH

E E

MIR

AT

ES

PR

OJE

CT

, D

UB

AI

ME

AS

UR

ED

& P

RE

DIC

TE

D T

IME

-S

ET

TLE

ME

NT

BE

HA

VIO

R

OFFIC

E

TO

WE

R

01

23

45

67

89

1011

12

50 40 30 20 10 0

Settlement (mm)

Predicted

T112T

111

1998T

ime

(months)

ME

AS

UR

ED

& P

RE

DIC

TE

D T

IME

-S

ET

TLE

ME

NT

BE

HA

VIO

R

HO

TE

L T

OW

ER

01

23

45

67

89

1011

12

50 40 30 20 10 0

Settlement (mm)

Predicted

T4

T15

1998T

ime

(months)

Measured

ME

AS

UR

ED

SE

TT

LEM

EN

T

CO

NT

OU

RS

H

OT

EL T

OW

ER

T1

T2

T3

T4

T5

T6

T7

T8

T9

T10

T11

T12

T13

T14

T15

T16

T17

T18

T19

T20

-8.0

-7.5

-8.3

-6.3

-6.0

-8.7

-7.9

-8.2

-8.3-7.2

-6.5

-5.8

-6.9-6.2

-7.3

-6.5

-7.4

-5.3

-7.4 -7.0

-6

-7

-7

-7

-7

-7

-7

-8

-6

-8-8

SE

NS

ITIV

ITY

OF IN

TE

RA

CT

ION

FAC

TO

RS

T

O A

NA

LYS

IS A

SS

UM

PT

ION

S

12

510

2050

100

0.10

0.2

0.3

0.4

Interaction Factor D

s/d

12534 CurveN

o.M

odulusof

Layer

belowM

Pa

Modulus

ofSoilbetw

eenPiles

toN

ear-PileValues

9090200700700

1.05.05.05.01.0

12345

Allow

ances made for:

Stiffer soil between piles

Stiffer soil below pile tips

Interaction is generally reducedM

arkedly.

Assum

ptions have a MA

JOR

influence on computed

interaction effects.

EFFE

CT

OF A

NA

LYS

IS A

SS

UM

PT

ION

S O

N

CO

MP

UT

ED

SE

TT

LEM

EN

T

0 20 40 60 80

100

120

140

160

OR

IGIN

AL

CA

SE

2C

AS

E 3

CA

SE

4C

AS

E 5

Settlement mm

Hotel Tow

er

TH

E E

MIR

AT

ES

PR

OJE

CT

, D

UB

AI

SO

ME

CO

MM

EN

TS

M

ajor efforts to obtain good site characterization

Design values of skin friction higher than

previously used in UA

E

CN

S direct shear testing proved very useful

Test pile behaviour reasonably w

ell-predicted

Foundation behaviour not well-predicted, but at

least conservative

TA

LLES

T B

UILD

ING

S (2000)

Dubai -2006

BU

RJ D

UB

AI T

OW

ER

Site P

hotograph S

eptember

2003

EA

RLY

CO

NS

TR

UC

TIO

N

July 2005

GE

OT

EC

HN

ICA

L PE

ER

R

EV

IEW

-SC

OP

E

Review

geotechnical information

D

evelop geotechnical model independently

Independent review

of Hyder foundation design

Independent calculations for foundation stability, settlem

ent, differential settlement

A

ssessment of pile load test data and final design

parameters.

Close cooperation betw

een Coffey &

Hyder m

aintained.S

ite visits, examination of site and borehole cores.

SIT

E C

HA

RA

CT

ER

IZA

TIO

N

30 boreholes

SP

T

60 PMT tests in 5 boreholes

6 standpipe piezom

eters

Geophysics

cross-hole tomography

SIM

PLIFIE

D P

RO

FILE4

Silty Sand

6C

alcarenite

17C

alcareous Sandstone

4.5G

ypsiferous Sandstone

40C

onglomeritic C

alcisiltite

22.5C

alcareous/Conglom

eritic

>47C

laystone/Siltstone

Base of Tow

er Raft

Base of Tow

er Piles

Typical C

ores 66m

depth

Typical C

ores 88m

depth

LAB

OR

AT

OR

Y T

ES

TIN

G

Conventional tests:

C

lassification (various)

UC

S

Point Load Index

M

odulus

Chem

ical

LAB

OR

AT

OR

Y T

ES

TIN

G

Advanced tests:

S

tress path triaxial

Resonant colum

n

Cyclic undrained triaxial

C

yclic simple shear

C

NS

HY

DE

R P

ILE D

ES

IGN

P

AR

AM

ET

ER

AS

SE

SS

ME

NT

S

kin friction via UC

S correlations &

CN

S test

data

Modulus value for settlem

ent prediction via correlations w

ith SP

T & U

CS

, pressuremeter,

shear wave velocity (w

ith allowance for strain

levels)

Non-linear behaviour via stress path tests

Judgem

ent employed

INIT

IAL P

ILE D

ES

IGN

Tow

er:

196 piles, 1.5m diam

eter, 47.5m long

Podium

:

750 0.9m diam

eter piles, 30m long

R

aft:

3.7m thick (tow

er)

HY

DE

R S

ET

TLE

ME

NT

P

RE

DIC

TIO

NS

R

EP

UTE

linear

P

IGLE

T -linear

V

DIS

P -linear &

non-linear

A

BA

QU

S

non-linear 3D FE

A

PR

ED

ICT

ED

LOA

D-

SE

TT

LEM

EN

T C

UR

VE

S50m

long 1.5m diam

. pile

0 10 20 30 40 50 60 70 80 90

010

2030

4050

6070

8090

Settlement m

m

Load MN

Hyder

Coffey

HY

DE

R -IN

ITIA

L TO

WE

R

SE

TT

LEM

EN

T P

RE

DIC

TIO

NS

Analysis

Settlem

ent mm

(Flexible cap)S

ettlement m

m(R

igid cap)R

EPUTE

p66

p)56

PIG

LET

-45

VD

ISP

-62

ABAQU

S72

46

CO

FFEY

IN

ITIA

L TO

WE

R

SE

TT

LEM

EN

T E

ST

IMA

TE

S

FLAC

(Axisym

metric)

73 m

m(m

aximum

)

P

IGS

74 m

m (m

aximum

)

LOA

D T

ES

T P

RO

GR

AM

3 static com

pression tests (1.5m dia.)

V

arious toe levels (35-55m long)

1 static com

pression test (0.9m dia.)

S

haft grouted

1 cyclic compression test (0.9m

dia.)

1 static tension test (0.9m dia.)

1 lateral load test

LOA

D T

ES

T P

RO

GR

AM

-O

UT

CO

ME

S1.5m

piles loaded to 2 times W

L0.9m

piles to 3.5 times W

L

No piles appeared to be approaching failure

S

kin friction values in excess of design assumptions

S

haft grouting effective, but not necessary

End bearing resistance not fully m

obilized

Axial stiffness greater than predicted

C

yclic axial loading had little effect

Lateral stiffness greater than predicted

CO

MP

AR

ISO

NS

S

KIN

FR

ICT

ION

-120

-100

-80

-60

-40

-20 0 20

0100

200300

400500

600700

800900

Skin Friction kPa

RL (DMD)

Original Design

Msd. Low

er Bound

Msd. Upper Bound

Recomm

ended (Hyder)

ME

AS

UR

ED

& P

RE

DIC

TE

D

PILE

HE

AD

ST

IFFNE

SS

ES

0

1000

2000

3000

4000

5000

6000

TP1TP2

TP3TP4

TP5TP6

Stiffness MN/m

Test Pile Number

At W

orking Load

At M

aximum

Load

Calc. At W

orking Load

ME

AS

UR

ED

& P

RE

DIC

TE

D

PILE

HE

AD

ST

IFFNE

SS

ES

Possible reasons for stiffer than expected

behaviour:

Use of polym

er drilling fluid.

Interaction between test pile &

reaction piles:

Analysis estim

ated that this interaction could cause a reduction in test pile settlem

ent of about 30%

With this allow

ance, axial stiffness more consistent

with E

mirates experience

TO

WE

R P

ILE LA

YO

UT

PR

ED

ICT

ED

SE

TT

LEM

EN

T

PR

OFILE

PR

ED

ICT

ED

SE

TT

LEM

EN

T

CO

NT

OU

RS

P

IGS

AN

ALY

SIS

LOA

D T

ES

TS

ON

WO

RK

S

PILE

S

Load tests carried out on some w

orks piles

Behaviour (axial) even better than test piles

P

redicted settlements could be conservative,

although group settlement depends on

stiffness of underlying layers

Measured T

ime-S

ettlement

Wing A

Measured T

ime-S

ettlement-

Wing B

Measured T

ime-S

ettlement

Wing C

Measured S

ettlement C

ontours -A

ugust 2006

Com

parison with P

redictions

Assum

ing 40% D

L and LL = 20% of D

L, in August 2006, applied load is about 33%

of design load

For linear behaviour, maxim

um predicted

settlement is:

H

yder22 m

m

Coffey

25 mm

M

easured16 m

m

Com

parison with P

redictions

Latest m

easurements:

Maxim

um m

easured settlement tow

ards the end of construction is about 40m

m

CO

MP

LET

ED

RA

FT

CO

NS

TR

UC

TIO

N P

RO

GR

ES

S

Early 2006Early 2007

September 2007

Gold C

oast Project -A

rtique

A

28 storey building on the G

old Coast

S

tructural Engineer

designed a fully piled to rock foundation system

P

iling contractor engaged C

offey to assess feasibility of piled raft

B

ased on results of feasibility, piling contractor engaged C

offey to optimize

piled raft design

Analysis of P

iled Raft

Feasibility

Detailed D

esign S

erviceability

Optim

ization

Detailed D

esign S

trength

OriginalD

esign

Con

tiguou

s bored pile wall

13

6 piles

foun

dedon

rock

Shear join

t between

core and podiu

m Slab0

.7m

thick

PEATY CLAY(SO

ME SAND)F-St

SANDD

SANDY CLAY (H) /CLAYEY SAND

MD

SAND WITH

SOM

E GRAVEL

MD

SANDY GRAVEL

METASILTSTO

NESW

0-5

-10

-15

-20

-25

-30

-35

-40

DESCRIPTION

Av.SPT

kPa(RAFT)

MPa

SuE

ss

E(PILES)

MPa

u p(RAFT)

MPa

kPafs

b fM

Pa

ASSUMED

BASE OF RAFT

60-

905.4

120100

9.9

1080

80.5

2022

0.7

60-

905.4

120100

9.9

14250

251.5

4060

2.0

25-

37.52.25

5048

4.1

100-

1509.0

200100

10.0

--

2000-

2000-

10.0RL (m)

SANDD-VD

M

Geotechnical

Model

Feasibility Results

Indicated that a raft foundation alone w

ould have a factor of safety of approxim

ately 10 for ultim

ate loading

Settlem

ents would govern. E

stimated to be of

the order of 35mm

to 60mm

The num

ber of piles would be of the order of

140

as per the foundation design supplied by contractor. H

owever, piles only 18m

long not 35m

Serviceability C

ase

123 piles (13 less)

M

aximum

raft settlem

ent of 44m

m

Maxim

umdifferentialsettlem

ent of 10m

m (1/400)

Outcom

es

N

umber of piles reduced by 10%

(13 piles)

Pile length reduced from 35m

to 18m

Total pile length reduced by 2767m

Settlement criteria (both total and

differential) satisfied

Potential variations in pile stiffness

compensated for by raft

CO

NC

LUS

ION

S

G

round conditions in Dubai are challenging for very tall

buildings

Modern m

ethods are being employed for:

In-situ testing

Laboratory testing

A

nalysis & design m

ethods

Sim

pler methods essential for checks on advanced num

erical analyses

U

se of piled rafts can lead to foundation economy

W

ith benefit of experience, predictive capabilities are im

proving

BU

T, reluctance remains to m

easure foundation performance

AC

KN

OW

LED

GE

ME

NT

S

Artique P

roject

Paran M

oyes

Frances Badelow

John S

mall

E

mirates P

roject:

Patrick W

ong

Jeff Forse

Paul G

ildea

Bob Lum

sdaine

Strath C

larke

Leanne Petersen

Burj D

ubai:

Frances Badelow

M

uliadi Merry

P

atrick Wong