Coffey Geotechnics

TALL BUILDINGS, DEEP FOUNDATIONS; MIDDLE EAST EXPERIENCES

The 2009 Terzaghi Oration

Harry PoulosCoffey Geotechnics

OUTLINE

Design Process for High-Rise Buildings Emirates Twin Towers Project

Investigations Design Load tests Tower foundation performance

Burj Dubai Foundation design Load tests Foundation performance

Gold Coast Building

Henry David Thoreau Walden (1854)

If you have built castles in the air,Your work need not be lost;That is where they should be.Now put the foundations under them.

FOUNDATION DESIGN PROCESS

Site characterization Geology Stratigraphy Quantification of relevant geotechnical parameters.

Based on: In-situ testing Laboratory testing Load testing

FOUNDATION DESIGN PROCESS

Foundation Type & Layout. Usually piles or piled raft

Based on: Foundation loadings Design criteria Construction issues Material availability

FOUNDATION DESIGN PROCESS

Design Issues1. Ultimate capacity2. Settlement3. Differential settlement & tilt4. Dynamic behaviour5. Earthquake response6. Structural strength of foundation elements7. Durability

LOCATION OF DUBAI PROJECTS

Emirates Site - 1996

SITE PLAN & BOREHOLES

INVESTIGATION PROGRAM

23 boreholes, up to about 80m depth (maximum) Trial pits SPT in upper layers Undisturbed sampling Water samples Permeability tests Pressuremeter tests Vertical seismic shear wave profiling Uniformity borehole testing

LABORATORY TESTING

Conventional laboratory & field tests Specialized testing

Site uniformity testing (geophysical) Cyclic triaxial testing

Effects of repetitive wind loading Stress path triaxial testing

Deformation parameters CNS testing

Ultimate shaft friction Resonant column testing

Dynamic shear modulus & damping

GEOTECHNICAL PROFILE & MODEL FOR EMIRATES SITE

Eu MPa E' MPa fs kPa fb MPa pu MPa

Silty Sand 40 30 18 0.2 0.1Silty Sand 125 100 73 1.5 1.5

Calcareous Sandstone 700 500 200 2.3 2.3

Silty Sand 125 100 150 1.9 1.9

Calcisiltite 500 400 450 2.7 2.7

" 90 80 200 2.0 2.0

" 700 600 450 2.7 2.7

FOUNDATION TYPES

Towers Piled raft foundations

Podium Piles, pile groups

LOAD TEST PROGRAM

Below each tower:

Compression test to 3000t, L=40m, d=0.9m Static tension test: L=25m, d=0.6m or 0.7m Cyclic tension test Lateral load test

Class A predictions made using assessed design parameters

PREDICTION METHODS

Axial Response Non-Linear boundary element analysis PIES program

Lateral Response Non-Linear boundary element analysis ERCAP program

Cyclic Tension Test Non-Linear boundary element analysis SCARP program

THE EMIRATES PROJECT, DUBAI

SETUP FOR COMPRESSION PILE TESTS

(-2.00)

(-0.50)(-1.50)

(-5.00)

(-10.0)

(-16.0)

(-20.0)

(-25.0)

(-30.0)

(-36.0)

(-40.0)

Working platform

Unit 1 - Silty sand

Unit 2 - Calcareous sandstone

Unit 4 - Calcisiltite

Unit 3 - Silty sand

20301285

900

Ground anchors

Reference beams

Footprint of the ground anchorsat the ground level

No. 1 Extensometer

No. 4 Strain gauges

22 Nos of ground anchors

3000t LOAD TEST WITH REACTION ANCHORS

Emirates Project, Dubai

LOAD-SETTLEMENT CURVES FOR PILE P3(H)

0 10 20 30 400

5000

10000

15000

20000

25000

30000

Appl

ied L

oad

(kN)

Settlement (mm)

PredictedMeasured

PREDICTED & MEASURED AXIAL LOAD DISTRIBUTIONS

0 5000 10000 15000 20000 25000 30000

-40-38-36-34-32-30-28-26-24-22-20-18-16-14-12-10

-8-6-4-202

Leve

l DM

D (m

)

Measured (15000 kN)Measured (23000 kN)Predicted

Load (kN)

LOAD-MOVEMENT CURVES FOR UPLIFT TEST

-35 -30 -25 -20 -15 -10 -5 00

1000

2000

3000

4000

5000

6000

Appl

ied L

oad

(kN)

MeasuredPredicted

Uplift (mm)

ULTIMATE SHAFT FRICTION FROM TESTS

0 100 200 300 400 500 600 700

50

40

30

20

10

0

Dept

h (m

)

Ultimate Skin Friction kPa

Design valuesDeduced from P3 (hotel) pile test (compression)Deduced from P1 (hotel) pile test (tension)Deduced from P3 (office) pile test (compression)Deduced from P1 (office) pile test (tension)

MEASURED & PREDICTED LATERAL LOAD-DEFLECTION CURVES

-10 -5 0 5 10 15 20 25

Appl

ied L

oad

(kN)

0

25

50

75

100

125

150

175

200

Displacement (mm)

PredictedMeasuredMeasured

MEASURED & PREDICTED LATERAL DEFLECTION vs DEPTH

-24

-22

-20

-18

-16

-14

-12

-10

-8

-6

-4

-2

0

2

Leve

l DM

D (m

)

-1.0 0 2.0 4.0 6.0 8.0 10.0 12.0

MeasuredPredicted (Load= 150 kN)

Deflection (mm)

ASSESSMENT OF PREDICTIONS

Class A predictions were in fair agreement Cyclic loading effects not well-predicted Assisted by:

Comprehensive investigation data Modern methods of lab & field testing Straight-forward mechanisms of behavior

EMIRATES TOWERS-FOUNDATION SYSTEMS

1.5m thick raft

102 piles for office

91 piles for hotel

1.2 & 1.5 m piles to 40-45 m

DESIGN METHODOLOGY

Limit State Approach Ultimate Limit State:

Static loads Repetitive wind loads

Serviceability Limit State: Settlements : max. 150mm Angular rotation: max. 1/350 long-term

TOWER FOUNDATION ANALYSES

GARP program for piled rafts Ultimate Limit State:

Used both factored & unfactored pile capacities Many load combinations

Serviceability Limit State Long-term settlements - GARP Short-term movements (wind) DEFPIG for axial & lateral

stiffness of individual piles in group Passed on to structural engineer for overall analysis

LOAD COMBINATIONS

Ultimate Limit State: 1.25G + 1.5Q 1.2G + 0.4Q + Wu 0.8G = Wu

Serviceability Limit State: G + 0.4QTotal of 18 load cases per tower

PILE INTERACTION DIAGRAM :OFFICE TOWER

DYNAMIC FOUNDATION RESPONSE

Required for seismic & wind response

Dynamic stiffness & damping from dynamic pile group analysis via Gazetas approach

MATLAB program developed for evaluation

SEISMIC EFFECTS

Liquefaction: Low very low risk

Ground Amplification of seismic motions: Category B assessed modest amplification

Potential for Site Settlements: Assessed to be low, 5-10mm under design

earthquake, unlikely to cause excessive downdrag loads on piles.

PREDICTED SETTLEMENT CONTOURS FOR OFFICE TOWER

0 5 10 15 20 25 30 35 40 45 500

5

10

15

20

25

30

35

40

45

50

y ax

is (m

)

x axis (m)100 110

110

110

120

120

120

120

130

130

130

110

110

55

100

Predicted Max.

Settlement = 134 mm

PREDICTED SETTLEMENT CONTOURS FOR HOTEL TOWER

0 5 10 15 20 25 30 35 40 45 500

5

10

15

20

25

30

35

40

45

50y

axis

(m)

x axis (m)

11 0

55

105

115

115

115

115

115

125

12512

5

105

105

105

105

105

Predicted Max.Settlement = 138 mm

THE EMIRATES PROJECT, DUBAI

THE EMIRATES PROJECT, DUBAI

MEASURED & PREDICTED TIME-SETTLEMENT BEHAVIOR OFFICE TOWER

0 1 2 3 4 5 6 7 8 9 10 11 12

50

40

30

20

10

0

Settl

emen

t (m

m)

Predicted

T112T111

1998Time (months)

MEASURED & PREDICTED TIME-SETTLEMENT BEHAVIOR HOTEL TOWER

0 1 2 3 4 5 6 7 8 9 10 11 12

50

40

30

20

10

0Se

ttlem

ent (

mm

)

Predicted

T4

T15

1998Time (months)

Measured

MEASURED SETTLEMENT CONTOURS HOTEL TOWER

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

SENSITIVITY OF INTERACTION FACTORS TO ANALYSIS ASSUMPTIONS

1 2 5 10 20 50 100

0.1

0

0.2

0.3

0.4

Inter

actio

n Fac

tor

s/d

1

2

53

4

Curve No.Modulus ofLayer below

MPa

Modulus of Soilbetween Piles

to Near-Pile Values

9090200700700

1.05.05.05.01.0

12345

Allowances made for:Stiffer soil between pilesStiffer soil below pile tips

Interaction is generally reducedMarkedly.

Assumptions have a MAJORinfluence on computedinteraction effects.

EFFECT OF ANALYSIS ASSUMPTIONS ON COMPUTED SETTLEMENT

0

20

40

60

80

100

120

140

160

ORIGINAL CASE 2 CASE 3 CASE 4 CASE 5

Settl

emen

t m

m

Hotel Tower

THE EMIRATES PROJECT, DUBAI

SOME COMMENTS

Major efforts to obtain good site characterization

Design values of skin friction higher than previously used in UAE

CNS direct shear testing proved very useful Test pile behaviour reasonably well-predicted Foundation behaviour not well-predicted, but at

least conservative

TALLEST BUILDINGS (2000)

Dubai - 2006

BURJ DUBAI TOWER

Site Photograph September 2003

EARLY CONSTRUCTION July 2005

GEOTECHNICAL PEER REVIEW - SCOPE

Review geotechnical information Develop geotechnical model independently Independent review of Hyder foundation design Independent calculations for foundation stability,

settlement, differential settlement Assessment of pile load test data and final design

parameters.Close cooperation between Coffey & Hyder maintained.Site visits, examination of site and borehole cores.

SITE CHARACTERIZATION

30 boreholes SPT 60 PMT tests in 5 boreholes 6 standpipe piezometers Geophysics cross-hole tomography

SIMPLIFIED PROFILE4 Silty Sand

6 Calcarenite

17 Calcareous Sandstone

4.5 Gypsiferous Sandstone

40 Conglomeritic Calcisiltite

22.5 Calcareous/Conglomeritic

>47 Claystone/Siltstone

Base of Tower Raft

Base of Tower Piles

Typical Cores 66m depth

Typical Cores 88m depth

LABORATORY TESTING

Conventional tests:

Classification (various) UCS Point Load Index Modulus Chemical

LABORATORY TESTING

Advanced tests:

Stress path triaxial Resonant column Cyclic undrained triaxial Cyclic simple shear CNS

HYDER PILE DESIGN PARAMETER ASSESSMENT

Skin friction via UCS correlations & CNS test data

Modulus value for settlement prediction via correlations with SPT & UCS, pressuremeter, shear wave velocity (with allowance for strain levels)

Non-linear behaviour via stress path tests Judgement employed

INITIAL PILE DESIGN

Tower: 196 piles, 1.5m diameter, 47.5m long

Podium: 750 0.9m diameter piles, 30m long

Raft: 3.7m thick (tower)

HYDER SETTLEMENT PREDICTIONS

REPUTE linear

PIGLET - linear

VDISP - linear & non-linear

ABAQUS non-linear 3D FEA

PREDICTED LOAD-SETTLEMENT CURVES

50m long 1.5m diam. pile

0

10

20

30

40

50

60

70

80

90

0 10 20 30 40 50 60 70 80 90

Settlement mm

Load

MN

Hyder

Coffey

HYDER - INITIAL TOWER SETTLEMENT PREDICTIONS

Analysis Settlement mm(Flexible cap)

Settlement mm(Rigid cap)

REPUTE 66 56

PIGLET - 45

VDISP - 62

ABAQUS 72 46

COFFEY INITIAL TOWER SETTLEMENT ESTIMATES

FLAC (Axisymmetric) 73 mm

(maximum)

PIGS 74 mm (maximum)

LOAD TEST PROGRAM

3 static compression tests (1.5m dia.) Various toe levels (35-55m long)

1 static compression test (0.9m dia.) Shaft grouted

1 cyclic compression test (0.9m dia.) 1 static tension test (0.9m dia.) 1 lateral load test

LOAD TEST PROGRAM-OUTCOMES

1.5m piles loaded to 2 times WL0.9m piles to 3.5 times WL No piles appeared to be approaching failure Skin friction values in excess of design assumptions Shaft grouting effective, but not necessary End bearing resistance not fully mobilized Axial stiffness greater than predicted Cyclic axial loading had little effect Lateral stiffness greater than predicted

COMPARISONS SKIN FRICTION

-120

-100

-80

-60

-40

-20

0

20

0 100 200 300 400 500 600 700 800 900

Skin Friction kPa

RL

(DM

D) Original Design

Msd. Low er Bound

Msd. Upper Bound

Recommended (Hyder)

MEASURED & PREDICTED PILE HEAD STIFFNESSES

0

1000

2000

3000

4000

5000

6000

TP1 TP2 TP3 TP4 TP5 TP6

Stiffness MN/m

Test

Pile

Num

ber

At Working Load

At Maximum Load

Calc. At Working Load

MEASURED & PREDICTED PILE HEAD STIFFNESSES

Possible reasons for stiffer than expected behaviour:

Use of polymer drilling fluid. Interaction between test pile & reaction piles:

Analysis estimated that this interaction could cause a reduction in test pile settlement of about 30%

With this allowance, axial stiffness more consistent with Emirates experience

TOWER PILE LAYOUT

PREDICTED SETTLEMENT PROFILE

PREDICTED SETTLEMENT CONTOURS PIGS ANALYSIS

LOAD TESTS ON WORKS PILES

Load tests carried out on some works piles

Behaviour (axial) even better than test piles

Predicted settlements could be conservative, although group settlement depends on stiffness of underlying layers

Measured Time-Settlement Wing A

Measured Time-Settlement-Wing B

Measured Time-Settlement Wing C

Measured Settlement Contours -August 2006

Comparison with Predictions

Assuming 40% DL and LL = 20% of DL, in August 2006, applied load is about 33% of design load

For linear behaviour, maximum predicted settlement is: Hyder 22 mm Coffey 25 mm

Measured 16 mm

Comparison with Predictions

Latest measurements:

Maximum measured settlement towards the end of construction is about 40mm

COMPLETED RAFT

CONSTRUCTION PROGRESS

Early 2006 Early 2007 September 2007

Gold Coast Project - Artique

A 28 storey building on the Gold Coast

Structural Engineer designed a fully piled to rock foundation system

Piling contractor engaged Coffey to assess feasibility of piled raft

Based on results of feasibility, piling contractor engaged Coffey to optimize piled raft design

Analysis of Piled Raft

Feasibility Detailed Design Serviceability Optimization Detailed Design Strength

Original Design

Contiguous bored pile wall

136 piles founded on rock

Shear joint between core and podium

Slab 0.7m thick

PEATY CLAY(SOME SAND)

F-St

SANDD

SANDY CLAY (H) /CLAYEY SAND

MD

SAND WITHSOME GRAVEL

MD

SANDY GRAVEL

METASILTSTONESW

0

-5

-10

-15

-20

-25

-30

-35

-40

DESCRIPTION Av.SPT kPa (RAFT)MPa

SuEs sE

(PILES)MPa

up(RAFT)

MPa kPaf s bf

MPa

ASSUMEDBASE OF RAFT

60 - 90 5.4 120 100 9.9

10 80 8 0.5 20 22 0.7

60 - 90 5.4 120 100 9.9

14 250 25 1.5 40 60 2.0

25 - 37.5 2.25 50 48 4.1

100 - 150 9.0 200 100 10.0

- - 2000 - 2000 - 10.0

RL (m

)

SANDD-VDGeotechnical

Model

Feasibility Results

Indicated that a raft foundation alone would have a factor of safety of approximately 10 for ultimate loading

Settlements would govern. Estimated to be of the order of 35mm to 60mm

The number of piles would be of the order of 140 as per the foundation design supplied by contractor. However, piles only 18m long not 35m

Serviceability Case 123 piles (13

less) Maximum raft

settlement of 44mm

Maximum differential settlement of 10mm (1/400)

Outcomes

Number 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

CONCLUSIONS

Ground conditions in Dubai are challenging for very tall buildings

Modern methods are being employed for: In-situ testing Laboratory testing Analysis & design methods

Simpler methods essential for checks on advanced numerical analyses

Use of piled rafts can lead to foundation economy With benefit of experience, predictive capabilities are

improving BUT, reluctance remains to measure foundation performance

ACKNOWLEDGEMENTS Artique Project

Paran Moyes Frances Badelow John Small

Emirates Project: Patrick Wong Jeff Forse Paul Gildea Bob Lumsdaine Strath Clarke Leanne Petersen

Burj Dubai: Frances Badelow Muliadi Merry Patrick Wong

TALL BUILDINGS, DEEP FOUNDATIONS; MIDDLE EAST EXPERIENCESOUTLINEHenry David Thoreau Walden (1854)FOUNDATION DESIGN PROCESSFOUNDATION DESIGN PROCESSFOUNDATION DESIGN PROCESSLOCATION OF DUBAI PROJECTSEmirates Site - 1996SITE PLAN & BOREHOLESINVESTIGATION PROGRAMLABORATORY TESTINGGEOTECHNICAL PROFILE & MODEL FOR EMIRATES SITEFOUNDATION TYPESLOAD TEST PROGRAMPREDICTION METHODSTHE EMIRATES PROJECT, DUBAISETUP FOR COMPRESSION PILE TESTS3000t LOAD TEST WITH REACTION ANCHORSLOAD-SETTLEMENT CURVES FOR PILE P3(H)PREDICTED & MEASURED AXIAL LOAD DISTRIBUTIONSLOAD-MOVEMENT CURVES FOR UPLIFT TESTULTIMATE SHAFT FRICTION FROM TESTSMEASURED & PREDICTED LATERAL LOAD-DEFLECTION CURVESMEASURED & PREDICTED LATERAL DEFLECTION vs DEPTHASSESSMENT OF PREDICTIONSEMIRATES TOWERS-FOUNDATION SYSTEMSDESIGN METHODOLOGYTOWER FOUNDATION ANALYSESLOAD COMBINATIONSPILE INTERACTION DIAGRAM :OFFICE TOWERDYNAMIC FOUNDATION RESPONSESEISMIC EFFECTSPREDICTED SETTLEMENT CONTOURS FOR OFFICE TOWERPREDICTED SETTLEMENT CONTOURS FOR HOTEL TOWERTHE EMIRATES PROJECT, DUBAITHE EMIRATES PROJECT, DUBAIMEASURED & PREDICTED TIME-SETTLEMENT BEHAVIOR OFFICE TOWERMEASURED & PREDICTED TIME-SETTLEMENT BEHAVIOR HOTEL TOWERMEASURED SETTLEMENT CONTOURS HOTEL TOWERSENSITIVITY OF INTERACTION FACTORS TO ANALYSIS ASSUMPTIONSEFFECT OF ANALYSIS ASSUMPTIONS ON COMPUTED SETTLEMENTTHE EMIRATES PROJECT, DUBAISOME COMMENTSTALLEST BUILDINGS (2000)Dubai - 2006BURJ DUBAI TOWERSite Photograph September 2003EARLY CONSTRUCTION July 2005GEOTECHNICAL PEER REVIEW - SCOPESITE CHARACTERIZATIONSIMPLIFIED PROFILETypical Cores 66m depthTypical Cores 88m depthLABORATORY TESTINGLABORATORY TESTINGHYDER PILE DESIGN PARAMETER ASSESSMENTINITIAL PILE DESIGNHYDER SETTLEMENT PREDICTIONSPREDICTED LOAD-SETTLEMENT CURVESHYDER - INITIAL TOWER SETTLEMENT PREDICTIONSCOFFEY INITIAL TOWER SETTLEMENT ESTIMATESLOAD TEST PROGRAMLOAD TEST PROGRAM-OUTCOMESCOMPARISONS SKIN FRICTIONMEASURED & PREDICTED PILE HEAD STIFFNESSESMEASURED & PREDICTED PILE HEAD STIFFNESSESTOWER PILE LAYOUTPREDICTED SETTLEMENT PROFILEPREDICTED SETTLEMENT CONTOURS PIGS ANALYSISLOAD TESTS ON WORKS PILESMeasured Time-Settlement Wing AMeasured Time-Settlement-Wing BMeasured Time-Settlement Wing CMeasured Settlement Contours - August 2006Comparison with PredictionsComparison with PredictionsCOMPLETED RAFTCONSTRUCTION PROGRESSGold Coast Project - ArtiqueAnalysis of Piled RaftOriginal DesignSlide Number 82Feasibility ResultsServiceability CaseOutcomesCONCLUSIONSACKNOWLEDGEMENTS