lecture 4 - jack-in pile

Some Malaysian Experience

By : Ir. Dr. Gue See Sew & Ir. Chow Chee Meng

Date: November 2009

JACKJACK--IN PILE DESIGNIN PILE DESIGN

G&P Geotechnics Sdn Bhd (G&P Geotechnics Sdn Bhd (www.gnpgeo.com.mywww.gnpgeo.com.my))

INTRODUCTIONINTRODUCTION

• Jack-in pile has been adopted in

Malaysia since early 1990s

• Currently, 600mm diameter spun pile with

working load up to 3000kN adopted for high-rise developments up to 45-storeys

HIGH CAPACITY

JACK-IN PILE MACHINE

HIGH CAPACITY JACKHIGH CAPACITY JACK--IN MACHINEIN MACHINE

• Maximum jack-in force up to 7000kN

• Width of machine up to 13.5m

• Required clearance for piling works:

5.5m to 6.9m (centre jacking)

• Clearance can be reduced to 1.5m to 2.0m for

side jacking but maximum jack-in force

reduced to approx. 3500kN

Typical schematic of high capacity jack-in pile machine

SMALLER CAPACITY

JACK-IN PILE MACHINE

Maximum Jack-in Force = 700kNSize = 4.8m x 3.6m

Maximum Jack-in Force = 1500kNSize = 6.6m x 5.0m

PROS & CONSPROS & CONS

PROS:

• Low noise and vibration

• Faster construction rates (vs. bored piles)

• Cleaner sites (vs. bored piles)

PROS & CONSPROS & CONS

CONS

• Strong and flat piling platform required

• Larger working area required (vs. driven piles)

• Limited pile size (vs. bored piles)

• Unable to go through intermittent hard layers/boulders (vs. bored piles)

GEOTECHNICAL CAPACITY OF PILES

• Malaysian conventional design practice:

Qag = (eq.1)

Qag = (eq.2)

b

bu

s

su

F

Q

F

Q+

g

busu

F

QQ +1.5 3.0

2.0


• Ultimate shaft resistance,

fsu = Ksu x SPT-N (in kPa)

• Ultimate base resistance,

fbu = Kbu x SPT-N (in kPa)

Typically,

Ksu = 2.5

Kbu = 200 to 400 (clay to sand)


• Design experience based on driven piles experience

• Valid for jack-in pile design?

BEHAVIOUR OF

JACK-IN PILES

BEHAVIOUR OF JACK-IN PILES

•Rankine Lecture by Prof. Mark Randolph (2003):

– Bored piles – zero residual pressures

– End-bearing can only be mobilised at relatively large displacement


–Driven and jacked in piles - significant residual pressures are locked in at the pile base during installation

–Higher end-bearing can be mobilisedat working load


•White & Lehane (2004):

–Greater number of cycles during pile

installation

larger reduction in shaft friction

Reduction in shaft

resistance!!!

White & Lehane, 2004


•Deeks, White & Bolton (2005):

– The measured jacking force during installation indicates plunging capacity

of the pile


– Jacked piles have a high base stiffness

– Stiffness of jacked piles

> 2 times stiffness of driven piles

> 10 times stiffness of bored piles

Less settlement at similar imposed load!!!

CASE HISTORIES

CASE HISTORIES

• Four different sites in Kuala Lumpur and Selangor

– Granite formation with silty SAND/sandy SILT

• Site A – 31-storey condominium

• Site B – 45-storey condominium

• Site C – 40 to 43-storey condominium

• Site D – 15-storey condominium

Site A

Site B

Site A

Site B

PILE DETAILS

• Pile size: φ φ φ φ400mm to φφφφ600mm

• Pile working load: 1520kN to 3000kN

• Pile termination criteria:

– Generally, jacked to 2.0 times working load

with holding time of 30 seconds (two cycles)

PILE PERFORMANCE

• All piles selected for testing (22 Nos.)

achieved the required test load within allowable settlement limits

• Pile length varies from as short as 6.5m to 37m

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15PILE TOP SETTLEMENT (mm)

0200400600800

10001200140016001800200022002400260028003000320034003600380040004200440046004800500052005400560058006000

AP

PL

IED

LO

AD

(kN

)φ600mm Spun Pile, Pile length = 20.7m

Site B

5.57mm 13.05mm

1.0*WL

2.0*WL

0 2 4 6 8 10 12 14 16 18 20 22 24 26PILE TOP SETTLEMENT (mm)

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

6500

7000

7500

8000

AP

PL

IED

LO

AD

(kN

)∅600mm Spun Pile, Pile length = 34.8m

Site D

8.48mm 23.84mm

Settlement at 2.5*WL

Residual settlement after unloading from 2.5*WL < 6.0mm

2.0*WL

1.0*WL


•From the pile load test results:

– Pile performance is satisfactory for pile

length as short as 6.5m


–Pile performance is satisfactory for

piles where preboring has been carried out

•Pile geotechnical capacity is a function of jack-in force during

installation

VALID!

TERMINATION CRITERION

1. Jack the pile to 2.0 times of the

design load for a minimum of two

cycles.

2. Pressure held for minimum 30

seconds with settlement not

exceeding 2mm.


• Is 30-seconds holding time too short to

ensure long-term settlement will not be a problem?


• Objective of specifying termination

criterion:

– To install the pile to the required depth to

achieve the required geotechnical

capacity!!!

• NOT for long-term settlement verification!!!


• Driven piles – long-term settlement of

piles cannot be directly assessed during pile driving

• Bored piles – verification of pile capacity and settlement depends solely on load

tests

JACK-IN PILE DESIGN

• Responsibility of designer to ensure

selected pile installation system can install the piles to the required level

• Termination criterion should be subjected to verification via maintained load test

– To verify capacity and settlement

characteristics

ADVANTAGES OF JACK-IN PILE


• Design experience based on driven piles experience

• Valid for jack-in pile design?


•Estimation of pile capacity using conventional pile design formula:

– Results of φ500mm spun pile on less optimistic load test results

– Pile capacity estimation based on Ksu = 2.5 and Kbu = 300

0 2 4 6 8 10 12 14 16 18 20 22 24PILE TOP SETTLEMENT (mm)

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

AP

PL

IED

LO

AD

(kN

)

∅500mm Spun Pile, Pile length = 16.5m

Pile show some signs of yielding


• Estimated pile working load (WL) based on conventional design = 1700kN

• Pile settlement at 1*WL (2300kN)

= 6.41mm

• Pile settlement at 2*WL (4600kN) = 21.83mm


•Conclusion:

–Pile capacity estimated based on driven piles experience tends to underestimate jack-in pile capacity


•Conclusion:

–Ultimate geotechnical capacity of jack-in piles is a function of maximum jack-in force during installation

SUMMARY

SUMMARY

High capacity jack-in pile

foundations have been

successfully adopted for high-

rise buildings

SUMMARY

Behaviour of jack-in piles:

–Mobilized shaft friction and

end-bearing resistance at

working load is expected to

be higher compared to

driven piles

SUMMARY

Recommended termination criterion

in weathered granite:

– Jacked to 2.0 times the design load for a minimum of two cycles

–Held for minimum of 30-seconds with settlement not exceeding 2mm

SUMMARY

Ultimate geotechnical

capacity of jack-in piles is a

function of maximum jack-in

force during installation

THANK YOU

FOR YOUR ATTENTION

Ir. Dr. Gue See Sew & Ir. Chow Chee Meng

G&P Geotechnics Sdn Bhd (G&P Geotechnics Sdn Bhd (www.gnpgeo.com.mywww.gnpgeo.com.my))

lecture 4 - jack-in pile

Documents