Lecture 4 - Jack-In Pile
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Transcript of Lecture 4 - Jack-In Pile
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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))
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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
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HIGH CAPACITY
JACK-IN PILE MACHINE
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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
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Typical schematic of high capacity jack-in pile machine
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SMALLER CAPACITY
JACK-IN PILE MACHINE
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Maximum Jack-in Force = 700kNSize = 4.8m x 3.6m
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Maximum Jack-in Force = 1500kNSize = 6.6m x 5.0m
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PROS & CONSPROS & CONS
PROS:
• Low noise and vibration
• Faster construction rates (vs. bored piles)
• Cleaner sites (vs. bored piles)
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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)
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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
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GEOTECHNICAL CAPACITY OF PILES
• 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)
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GEOTECHNICAL CAPACITY OF PILES
• Design experience based on driven piles experience
• Valid for jack-in pile design?
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BEHAVIOUR OF
JACK-IN PILES
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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
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BEHAVIOUR OF JACK-IN PILES
–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
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BEHAVIOUR OF JACK-IN PILES
•White & Lehane (2004):
–Greater number of cycles during pile
installation
larger reduction in shaft friction
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Reduction in shaft
resistance!!!
White & Lehane, 2004
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BEHAVIOUR OF JACK-IN PILES
•Deeks, White & Bolton (2005):
– The measured jacking force during installation indicates plunging capacity
of the pile
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BEHAVIOUR OF JACK-IN PILES
– 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!!!
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CASE HISTORIES
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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
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Site A
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Site B
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Site A
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Site B
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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)
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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
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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
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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
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BEHAVIOUR OF JACK-IN PILES
•From the pile load test results:
– Pile performance is satisfactory for pile
length as short as 6.5m
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BEHAVIOUR OF JACK-IN PILES
–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!
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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.
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TERMINATION CRITERION
• Is 30-seconds holding time too short to
ensure long-term settlement will not be a problem?
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TERMINATION CRITERION
• 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!!!
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TERMINATION CRITERION
• 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
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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
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ADVANTAGES OF JACK-IN PILE
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GEOTECHNICAL CAPACITY OF PILES
• Design experience based on driven piles experience
• Valid for jack-in pile design?
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GEOTECHNICAL CAPACITY OF PILES
•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
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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
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GEOTECHNICAL CAPACITY OF PILES
• 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
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GEOTECHNICAL CAPACITY OF PILES
•Conclusion:
–Pile capacity estimated based on driven piles experience tends to underestimate jack-in pile capacity
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GEOTECHNICAL CAPACITY OF PILES
•Conclusion:
–Ultimate geotechnical capacity of jack-in piles is a function of maximum jack-in force during installation
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SUMMARY
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SUMMARY
High capacity jack-in pile
foundations have been
successfully adopted for high-
rise buildings
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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
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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
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SUMMARY
Ultimate geotechnical
capacity of jack-in piles is a
function of maximum jack-in
force during installation
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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))