Building the Foundations of Australia

Building the Foundations of Australia www.pilingcontractors.com.au

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Presentation

EXTREME COMPRESSION AND TENSION LOADS

FOR THE SOUL TOWER, A 77 STOREY

APARTMENT BUILDING ON THE GOLD COAST

12th May 2010, 9.15 pmIQPC Piling & Deep Foundations Conference Melbourne

Hotel Bayview Eden, MelbourneSpeaker: Martin Larisch (Piling Contractors)

Extreme Compression & Tension Loads for the Souls Tower on the Gold Coast

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Site location of Soul in Surfers Paradise, QLD

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Finished appearance in Surfers Paradise, QLD

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Site location of the project in Surfers Paradise, QLD

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77 storey apartment building with a retail area surrounding the main

tower

Third highest residential building in Australia (277m)

Beach front location in the heart of Surfers Paradise

Demolition works started in December 2007, proposed completion

of the

project mid of 2011

Main Contractor of the D&C project is Grocon Constructors (QLD)

Pty Ltd

Piling works awarded as D&C package to Piling Contractors Pty Ltd

in

December 2007


Introduction: About the Soul Project

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Developer employed McConnell Consulting in 2005 to carry out a soil

investigation comprising 4 boreholes with SPTs and undisturbed sampling in

soils and NMLC triple tube coring in rock

Point load index tests on rock samples

Classification tests on soil samples

Noted that the concept was for a very tall structure with unusually deep

basements


Introduction: Early Site Investigation

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Grocon employed Golder Associates in 2007 to review Site Investigation and

make recommendations:

Data from this site and two adjacent sites considered in new report

Suggestion of ranges of UCS and Modulus

Use of ROCKET to determine ranges of shaft friction

Base resistance greater than available concrete strength

Recommendation of additional drilling


Introduction: Site Investigation used for pile design

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Introduction: Piling works

Pile installation was carried out in four stages from January – Sept. 2008

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Pile layout plan - Pile installation

Stage ICFA piles 01/2008

Stage IItower piles03-08/2008

Stage IIICFA piles

05-07/2008

Stage IVCFA piles09/2008

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Tower piles

Pile layout plan - Location of tower piles

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Bored piles for the main tower

44 large diameter bored piles (installed under bentonite) for the main

tower

pile cut off levels 9m & 14m below working platform

plunged steel columns required for 21 piles

pile Ø 1500mm, 1800mm and 2200mm

drilling depths up to 45m

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1800mm

1500mm

Pile Layout Plan - Pile diameters tower piles

2200mm

column

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Site Geology - Site location of Soul in Surfers Paradise, QLD

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Site Geology - Assumed soil profile

Typical site conditions detailed in the chart below:

ELEVATION BRIEF DESCRIPTION

+5m to -1.5m Fill (loose silty sand and clayey sand)

-1.5m to -21m Sand (dense to very dense with some sandy clay lenses)

-21m to -33m Sandy clay and clayey sand (ranging from stiff to medium dense)

-33m to -36m Greenstone / Argillite (very weak)

-36m to -48m Argillite (Neranleigh - Fernvale Group)

-48m to -60m Argillite (Neranleigh - Fernvale Group) but RQD > 70% (assumed)

below -60m Massive Argillite (assumed)

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Site Geology - Further Site Investigation by Grocon / Golder

One additional borehole drilled to 42m depth (-44.5m AHD)

Results confirmed previous investigation

Pile bases had to be very clean to mobilise end bearing

100% requiring a comprehensive cleaning system and SID

Some base debris, requiring sweep airlift and purpose built cleaning

buckets; bentonite with <2% sand content

Shaft friction only, requiring conditioning of drilling fluid and cleaning

bucket

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Site Geology - Assumed soil profile

Golders0

10

20

30

40

50

60

70

BasementSandGreenstoneArgillite

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Site Geology - Summary point load tests

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0-1.0

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

S-1S-1S-2S-3S-3S-4S-4S1 AxialS1 DiametralS2 DiametralBH1

Point Load Index (MPa)

Dept

h be

low

top

of A

rgill

ite (m

)

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Site Geology - Design parameters

Point load tests from two independent soil investigation reports

indicate

high strength to very high strength Argillite in the target founding zone

for pile toe levels

Piles to be designed with rock sockets of at least one pile diameter

into

high strength Argillite or better (UCS between 20-30 MPa)

Piles with high tension loads to be designed and constructed with

longer rock sockets of 3.5m

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Site Geology - The following parameters were recommended:

Depth Material UCS (MPa) E (GPa)

9 to 38.7m Very dense sand - 0.05 to 0.1

38.7 to 41.5m Greenstone 5 to 10 0.5 to 1.0

> 41.5m Argillite 20 to 30 4 to 6

Ultimate shaft resistance (kPa)

Depth Material Minimum Maximum

9 to 38.7m Very dense sand 100 150

38.7 to 41.5m Greenstone 500 750

> 41.5m Argillite 1200 2500

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Site Geology - Geotechnical design by Piling Contractors

Piling Contractors appointed PSM to carry out geotechnical design review

Examined soil profile

Carried out FE modelling

Minor modifications to socket length suggested and accepted by MJ Civil

Looking at settlement and differential settlement, and at tension capacities

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43

02468

1012141618

DL + 40% LL settlement Serviceability settlement

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Building loads for the Soul tower

Vertical compression load of building (MN)

Vertical tension load (MN)

Lateral load (MN)

DL + 40% LL Serviceability Ultimate

1060 1573 2170

Ultimate

213

Ultimate

65.5

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Pile loads (ULS) for the tower piles

1500mm piles 18-32MN in compression, average 24-

26MN

0-3MN in tension


44MN

0-5MN in tension


60MN

0-18.6MN in

tension

Pile P11 (Ø2200mm) with ULS load of 90MN in compression

Pile P14 (Ø2200mm) with ULS load of 18.6MN in tension

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Pile loads (ULS) for the tower piles

10000 20000 30000 40000 50000 60000 70000 80000 90000 1000000

5000

10000

15000

20000

25000

CP pilesP piles

Ultimate compressive load (kN)

Ultim

ate

tens

ile lo

ad (k

N)

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Major technical challenges of the project

Tower piles with very high compression and tension loads - ULS pile

loads

up to 90MN (compression) and 18.6MN (tension) per pile

Requirements for elimination of structural concrete cracking under

tension loads→ Minimum characteristic concrete principal tensile strength (f’ct)

shall be 0.4√ fc’

Pile installation within tolerances is imperative

Installation of plunged columns in tension piles

Pile cut off levels located 9m and 14m below working platform

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Options for compression loads

Driven piles

Not suitable for the intensity of loading

Raft foundation (stiffened raft/slab or piled raft)

Considered by McConnell Consulting for basement/podium

foundations

CFA piles

Used for podium foundations

Bored piles socketed into rock

Used for tower foundations

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Options for tensile loads

Driven piles

Not suitable for the magnitude of loading, joints etc

Raft foundation (stiffened raft/slab or piled raft)

Not suitable for uplift in excess of dead weight

CFA piles

Problems with full length reinforcement

Bored piles socketed into rock

Used for tower foundations

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Pile Design - Piling works as D&C contract

Piling Contractors first tender proposal

Pile diameter Quantity

1200mm 2

1500mm 15

1800mm 13

2200mm 10

3000mm 3

Pile diameter Quantity

1500mm 7

1800mm 18

2200mm 19

Revised and optimized proposal

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Why was the reduction of 3000mm to 2200mm piles important?

3000mm piles with 86% more volume (influences drilling rates,

cleaning

of drilling fluid, storage capacities, steel and concrete quantities)

3000mm piles with 36% deeper rock sockets

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How can the tension capacity of bored piles be improved?

→ Use of high strength concrete (fc’ > 85MPa) for the pile shaft

providing additional tensile capacity

Workability criteria

several 1500mm and 1800mm piles were installed and poured

successfully with the 65MPa mix (no blockages)

slump of 260mm, spread 600mm

workability for 8-10 hours to ensure contingency

delivery and supply of concrete without delays

no concrete bleeding or segregation observed

concrete strength achieved

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Use of high strength concrete

Plunged column installation

site trial with a test column in a 1500mm pile to verify minimum

plunged depth of 10m into concrete

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Use of high strength concrete

Plunged column installation

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Concrete Design Requirements

Design criteria

according to minimum characteristic concrete principal tensile

strength (f’ct) > 0.4√fc’ and maximum tension loads (ULS) of 19MN

for a pile diameter of 2200mm (cross section of 3.80m2) →

f’ct > 5MPa

Previous experience suggested that the tensile strength of

concrete is about 5-8% of the compressive strength → fc’ ~ 65-

100MPa

Concrete supplier tested 6 samples from an earlier project where

a 70MPa mix achieved 100-110MPa compressive strength after 56

days → f’ct > 6-7MPa

Preparation of a 85MPa concrete mix to target 100-110MPa

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Trial with three mixes

Minimum compressive strength of 85MPa

Minimum tensile strength of 5MPa

Workability of 8-10 hours

All mixes designed not to absorb / release

water from / to environment

Proposed trial mixes for the 85MPa mix

Three different trial mixes:

S851FLL based on workability criteria of 65MPA mix

S851FLLFib with added synthetic fibres (extra tension capacity)

S851FLLretrial with reduced hydration stabilizing admixture

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Concrete workability criteria

Testing if the mix is homogeneous

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Concrete workability criteria trial mixes - S851FLL Fib

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Concrete workability criteria trial mixes - spread test S851FLL Fib

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Concrete workability criteria trial mixes

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Indirect Tensile Strength Test AS1012.10-2000 (Splitting Test)

Taking a sample on site Put sample into test jig under hydraulic

cylinder

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Different test set up Sample

in test frame

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Stress distribution

Cracked samples

inside a sample

showing typical failure mode

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Results

5 MPa

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Site Trial

Test workability on site on a compression pile (1500mm)

1500mm pile with a plunged column test installation

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Site Trial

Excellent workability criteria for SF851FLL

Plunged column installation up to 10m into concrete (suspend

column)

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Site Trial

Workability criteria for SF851FLL Fib critical

Fibres might get caught on reinforcement cage

or plunged column shear studs

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Site Trial - Summary:

Successful site trial

Risk that fibers get caught on reinforcement cage or plunged

columns considered as too high, fibres reduced workability of the mix

Workability criteria of SF851FLL excellent

Early tensile strength of SF851FLL > 5MPa after 7 days

Early compression strength of SF851FLL > 80MPa after 7 days…

1500mm

2200mm

1800mm

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f’c>85MPa

Overview of all piles with high strength concrete (fc’>85MPa)

column

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Tensile Test Results

76 tensile strength results were taken for the whole project:

3 tensile and 3 compressive samples for every 50m3

of 85MPa concrete

2 early strength tests after 2 days: f’ct = 5.2 – 5.4MPa

23 early strength tests after 7 days: f’ct = 4.3 – 6.4MPa

8 strength tests after 28 days: f’ct = 6.6 –

7.5MPa

43 strength tests after 56 days: f’ct = 6.6 –

8.5MPa

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Summary Tensile Strength Results

Summary Tensile Strength Results

0

1

2

3

4

5

6

7

8

9

0 10 20 30 40 50 60Age of probe [days]

Indirect

Tensile

Str

ength

[M

Pa]

test results after 56 days



Minimum tensile strength requirement of 5MPa after 28 days

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Quality Control – Concrete Displacement Records

theoretical volume

actual volume

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Pile Layout Plan – Integrity Tests

1500mm

2200mm

1800mm

low strain

cross hole

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Quality Control - Cross Hole Sonic Logging

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Quality Control - Cross Hole Sonic Logging

1-5 1-4

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Quality Control – Low strain integrity tests (PIT)

Low strain integrity tests (PIT) to be carried on several piles

randomly

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Lessons Learned

Constant maintenance of drill tools due to high strength rock…

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Lessons Learned

Working under limited access (1/2)

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Lessons Learned

Working under limited access (2/2)

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Lessons Learned

Special challenges when working in Surfers Paradise……

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Future Outlook::

Drilling Technology:

Bauer BG28 used for the SOUL project

machine worked on upper limit

stronger Bauer BG40 rig now available

390kNm torque (+42%)

300kN winch capacity (+20%)

140T operational weight (+48%)

433kW engine power (+22%)

pile Ø3000mm possible

BG28SOUL

BG40

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Conclusion:

Use of high strength concrete fc’>85MPa can be used successfully for

bored piles if:

concrete mix is designed & tested for project specific circumstances

concrete supply and delivery without delays

highly experienced site crew and concrete supplier

innovative and cooperative client who is open for new ideas

Building the Foundations of Australia www.pilingcontractors.com.au

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THANK YOU

FOR YOUR

ATTENTION


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