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Design and testing of bored pile foundation to the 2nd Penang Bridge, Malaysia By
Sing-lok CHIU, AECOM
Zheng-ru Fang, CHEC Construction (M) Sdn Bhd (CHEC)
Kang HUANG, China Highway Planning and Design Institute (HPDI)
Presented by Dr SL Chiu
Technical Director, Geotechnical Hong Kong
AECOM
November 16 2011 Page 1
Contents
16 November 2011
•Overview of bored pile design approaches
•Design of bored piles for the 2nd Penang Bridge
•Site characteristics
•Design and instrumentation of the trial bored pile
•Static load test on the trial bored pile
•Test results
•Conclusion
Page 2
2nd Penang Bridge under construction
16 November 2011
Cable-stayed section of the 2nd Penang Bridge over
the main navigation channel
Page 3
16 November 2011
21 bored piles of 2.0 ~ 2.3 m
in diameter and socketted in
to sound granite bedrock at
about 110m deep below sea
bed
batu kawa
Pier P25 Pier P26 240 m
150m x 30m
Page 4
Overview of bored pile design approaches
The load resistance capacity of a bored pile is mainly
derived from the pile shaft and base resistances
(Whitaker, 1976):
16 November 2011
Q ultimate = Q shaft + Q base
Page 5
Given that:
16 November 2011
•There are different resistance and settlement
relationships of the shaft and base
•It is advisable that different load factors be
applied to the calculated ultimate resistance of the
shaft and the base (BS8004, 1985).
Page 6
Partial factors or global factor of safety are applied to give allowable capacity of the bored pile
16 November 2011
Q allowable = Q shaft /FS+ Q base /Fb
Or
Q allowable = (Q shaft + Q base )/F
Page 7
Partial factors and global factor for bored pile design
16 November 2011
•Skempton (1966) suggested Fs= 1.5 and Fb= 3
•BS 8004 (1985) suggested that the global factor
of safety for a single pile is often required to be
between 2 and 3
Page 8
Burland and Cook (1974) suggest for bored pile in stiff clay -an overall load factor of 2 , and
- a minimum factor of safety 3 on the base
resistance be adequate.
Q allowable = Q shaft + Q base /3
Or
Q allowable = (Q shaft + Q base )/2, whichever is less
16 November 2011
Page 9
Estimate of shaft and base resistance
Empirical approaches based on:
•In-situ tests results e.g., SPT N-value (no. of blows)
fs = α + βN kN/m2 (e.g., α = 0, and β= 1 to 5
for BP in cohesionless soil)
•Laboratory strength test results, e.g., undrained
strength, Cu (α- method) and friction angle, φ’ (β-
method ): fs = αcu and fs =βσv’
16 November 2011
For piles in soils (Poulos, H. G. 1989)
Page 10
16 November 2011 Page 11
Clay fs = αcu α=0.45 (London clay) α=0.7 times value for
driven displacement pile
Skempton(1959) Fleming et al.(1985)
fs = K tan δσv’ K is lesser of K0 or 0.5(1 + K0)
K/K0 = 2/3 to 1; K0 is function of OCR; δ depends on interface materials
Fleming et al.(1985) Stas and Kulhawy (1984)
Silica sand fs =βσv’ β=0.1 for φ’= 33˚ 0.2 for φ’=35˚ 0.35 for φ’=37˚ β= F tan (φ’-5˚) where F = 0.7 (compression) & 0.5 (tension)
Meyerhof (1976) Kraft & Lyons (1974)
Loose to medium sand
fs =βσv’ β=0.2 to 0.6 *Hong Kong (Geo 2006)
Estimate of shaft and base resistance For piles in soils (cont’d) Chinese Standard (JGJ 94-2008) and German
Code (DIN 1054:2005) suggest use of presumed
values based on site specific factors including soil
types, physical and mechanical properties of the
soils and rocks as well as pile length
16 November 2011
Page 12
DIN 1054:2005
16 November 2011
CPT , qc in
MPa
Cohesionless
soil, fs in kPa
Undrained
strength, Cu in
kPa
Cohesive soil,
fs in kPa
5 40 25 0
10 60 100 40
≧15 120 ≧200 60
Note: Intermediate values are obtained by linear interpolation
(after Vrettos, 2007)
Page 13
16 November 2011
Settlement to
base
diameter
ratio,
S/Dbase
Pile base resistance, fb, in MPa for bored piles in
cohesionless soils
At an average tip cone resistance, qc of the CPT in MPa
10 15 20 25
0.02 (40mm
if D= 2.0m)
0.7 (or 700
kPa)
1.05 1.4 1.75
0.03 0.9 1.35 1.8 2.25
0.1* 2.0 3.0 3.5 4.0
DIN 1054:2005
Note: * limiting settlement
Intermediate values are obtained by linear interpolation
(after Vrettos, 2007)
Page 14
16 November 2011
Settlement to
base
diameter ratio,
S/Dbase
Pile base resistance, fb, in MPa for bored piles in
cohesive soils
At an average shear strength, Cu of the undrained soil
in MPa
0.1 0.2
0.02 0.35 0.9
0.03 0.45 1.1
0.1* 0.8 1.5
DIN 1054:2005
Note: * limiting settlement;
Intermediate values are obtained by linear interpolation;
for bored piles with widened base, values shall be reduced to 75%
(after Vrettos, 2007)
Page 15
Chinese foundation code, JGJ94-2008
16 November 2011
Soil Type Soil properties Presumed values of
fs in kPa
Clay IL>1
0.75<IL<1
05<IL<0.75
21～38
38～53
53～68
Silty fine sand 10<N≦15
15<N≦30
N>30
22～46
46～64
64～86
Coarse sand 15<N≦30
N>30
74～95
95～116
Note: Intermediate values are obtained by linear interpolation
an abridged version of the original Table in JGJ94-2008
Page 16
16 November 2011
Soil Type Soil
properties
Presumed values of fb in kPa for different pile
length in m
5 ≤ L<10 10 ≤L<15 15 ≤L <30 30 ≤L
Clay 0.75<IL<1
05<IL<0.75
150 ~250
350 ~450
250 ~300
450 ~600
300 ~450
600 ~750
300 ~450
750 ~800
Silty fine
sand
10<N≦15
N> 15
350~500
600~750
450~600
750~900
600~700
900~1100
650~750
1100~1200
Coarse
sand
N>15 1500~1800 2100~2400 2400~2600 2600~2800
Chinese foundation code, JGJ94-2008
Note: an abridged version of the original Table in JGJ94-2008
Page 17
Estimate of shaft and base resistance For bored pile founded on or socketted in sound rock Because of the great difference in stiffness of soil
and the sound rock, the load carrying capacity is
mainly derived from the end bearing capacity of pile
on/in rock.
16 November 2011
Page 18
For bored pile founded on or socketted in sound rock (cont’d) The estimation of end bearing is mainly based on
empirical methods. Presumed values for safe
working stress are recommended, being a function
of the uniaxial compression strength, qc, of the rock:
16 November 2011 Page 19
16 November 2011
Uniaxial compression
strengthen of rock in
Mpa
Pile base resistance,
fb, in MPa
Pile shaft resistance,
fs, in MPa
0.5 1.5 0.08
5 5.0 0.5
20 10.0 0.5
DIN 1054:2005
Note: Intermediate values are obtained by linear interpolation.
Page 20
16 November 2011
h/d 0 0.5 1.0 2.0 3.0 4.0
Soft
rock
ζr = 0.6 0.8 0.95 1.18 1.35 1.48
Hard
rock
0.45 0.65 0.81 0.9 1.0 1.04
For bored piles socketted in bed rock,
JGJ 94-2008
Where
h/d- socket depth (h) to pile diameter (d)
Soft rock- UCS, frk < 15MPa
Hard rock- UCS, frk >30MPa
Page 21
Where ,
Qrk, is the combined shaft and base resistance of the rock socket
Ap, pile base area;
frk the uniaxial compression strength (UCS) of the bedrock, and
ζr a factor taking into account of the combined effect of base and
shaft resistance of pile in the socket, depending on the ratio of h/d
16 November 2011
Qrk = ζr frk Ap
Page 22
Design of bored pile foundation for the 2nd Penang Bridge
Design Brief
16 November 2011
For compressive loads:
Q= (Qs/2) + (Qb/3); or
Q= (Qs + Qb)/2.5, whichever yields the lowest working capacity;
For tensile loads (uplifts):
Q=Qs/3
Where Q is the allowable pile capacity (kN), Qs is the ultimate shaft
friction (kN), Qb is the ultimate end bearing (kN).
Page 23
To evaluate the shaft resistance (Qs) and end bearing (Qb),
the following relationships with SPT-N value as suggested by
Meyerhof (1976) are used:
Qs = Ks* N*As, or = fs *As (Ks= 2.0 for cohesionless soils)
Qb= Kb*Nb*Ab, or = fb * Ab (Kb= 250 for silty soil
and 400 for sandy soil)
SPT-N value is limited to 75
16 November 2011
Page 24
16 November 2011
For end-bearing bored piles on sound bed rock
Qb= quc * (RQD)2*Ab
Where Qb = the ultimate load bearing capacity at pile base,
quc = unconfined compressive strength
RQD= Rock Quality Designation
For bored piles socketted in sound bed rock,
Qs= fs,*As,
where Qs = the ultimate load bearing capacity of the
socket be limited to:
fs= 75 kPa for RQD between 0 to 25%
= 150 kPa for RQD between 25 to 50%
=350 kPa for RQD> 50%
Page 25
An instrumented trial bored pile of diameter of 2.0~2.3 m and
about 125m in length was installed and tested with an
Osterberg Cell (O-cell) planted in the test bored pile during
construction.
16 November 2011
The determination of design parameters
for the bored pile foundation
Page 26
Site Characteristics
16 November 2011
A water depth of about 12m- sea bed
@ level -9.95m (reduced level)
Soft to very soft marine mud, 18 m in
thickness with SPT-N value<1
medium dense to very dense , Alluvial
fine to coarse sand with SPT-N values
increasing with depth to about 100 m
Completely weathered granite
Slightly weathered granite bedrock,
Grade II -120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
0 10 20 30 40 50 60 70 80 90 100 110 120
Dep
th i
n m
N-Value
Pier 25 (ABH1)
Soft mud
Depth zero = seabed level (reduced level -9.95
m)
loose to medium dense medium to coarse sand Nave= 10
medium dense medium to coarse sand Nave= 22
medium dense to dense medium to coarse sand Nave= 41
CDG
slightly weathered granite
Average SPT-N value profile
Φ 2.3m
Φ 2.0m
Page 27
16 November 2011
1.88m
level of pile toe
lower plate of load cell
Upper plate of load cell
sea bed
pile head
Load cell
112.75m
115.07m
0.44m
2.3m
2.0m
-8.50m
-9.95m
-38.50m
-121.69m
-123.57m
Reinforcement details:
Main bars:T32 @ 150mm c/c
Binder: T16 binder @ 150 to
300 mm c/c
Concrete cover: 75mm
Concrete Grade: G40/20
Construction of the test
bored pile
Page 28
16 November 2011
data
acquisition system
displacement transducers
hydraulic pump withpressure gauge
oil pipe
steel telltale rods
load cell
reference beam
shaft
side
shear
shaft end bearing
telltale casings
Instrumentation
of the test bored
pile
Page 29
16 November 2011
Type
Outer
diameter
(mm)
Diameter of
Cylinder
(mm)
Upper plate
thickness
(mm)
Lower plate
thickness
(mm)
Height
(mm)
max. stroke
(mm)
YG565-
1002×5 1800 500 40 40 440 220
Instrumentation of the test bored pile
5 hydraulic jacks of
a maximum stroke
of 200mm
Access of tell-tale rods
to bottom plate
Page 30
16 November 2011
Instrumentation of the test bored pile
TGCL-1
Vibrating wire type strain
gauge
Operational range: 2500 με
Resolution: 0.4 ~ 1 με
Waterproof – 150m under
water
Temperature: -20 to 80℃
WDL-50TZ
Linear Variable
Differential
Transformer (LVDT)
displacement
transducers
Page 31
19 20 21
P25 test pile
refrence beam
Reference pile 2
Unit：mm；
refrence pile 1
16 November 2011
Layout of testing platform
Page 32
16 November 2011
6 LVDT displacement transducers were installed,
namely
•2 for upward movements of the top plate of load cell
•2 for downward movements of the bottom plate of
load cell
•2 for upward movements of the pile head.
Instrumentation of the test bored pile
Page 33
16 November 2011
Page 34
O-Cell
Vibrating wire type
strain gauges
Tell tale access
Static load test of the trial bored pile
16 November 2011
NO.
Design
strength of
concrete
Location
in
Chainage
Socket
depth
(m)
Pile
Diameter
（m）
Anticipat
ed Level
of Pile
Toe（m）
Level of
pile top
（m）
Bottom
Level of
Load Cell
Box（m）
Working
Load
（kN）
P25 G40/20 CH+980.
96 4.0 2.0~2.3 -123.250 -3.245 -121.690 25500
Note:
•The diameter is 2.3 meters from level -3.245 to -38.500; and the diameter is 2 meters from level -
38.500 to -123.25
• reduced level referred to NGVD
NO. Type of
drilling rig
Verticality
Concrete
filling rate
Density of
slurry
Level of
pile top
（m）
Level of
pile toe
（m）
Socket
depth
(m)
Filter
cake
thickness
（mm）
P25 ZJD-300
1/1000
1.07
1.03～
1.10 -8.50 -123.57 4.32 2.2
Page 35
Static load test of the trial bored pile (cont’d)
16 November 2011
Load
increment
No.
Percentage
of Working
Load
(%)
Test load, in
kN,
Q
Applied load at
load cell in kN,
Qup
Minimum
Maintained
Time
(hour)
1 to 11 17 to 183 4250 to 46750 5046 to 21473 2
12 200 51000 23115 48
12 to 15 -50 12750 8332 1
16 0 0 0 ≥3
Note: design working load= 25500 kN; maximum design testing load = 51000
kN
Page 36
16 November 2011
Test Results
When loaded from 18187 kN to 19830 kN, the pile moved upward for more than 46mm (i.e., from 13.10 mm to 59.75 mm while the lower part moved downward for 0.6mm (i.e., from 4.21mm to 4.81mm). As the test load was released to zero, the residual settlements measured at the top and bottom plates of the O-cell were 24.33mm and 0.06mm respectively. The residual movement remained at the pile head was 19.84mm
Page 37
Test results (cont’d)
16 November 2011
Equivalent load settlement curve for the test pile
subjected to equivalent head down loading
Page 38
38101 kN
32.24 mm
Test results (cont’d)
16 November 2011
0
20
40
60
80
100
120
0 10000 20000 30000
Axial force（kN）
dept
h（m）
6689
8332
9974
11617
13260
14902
16545
18187
19830
-120
-100
-80
-60
-40
-20
0
0 50 100 150
Dep
th in
m
Max shaft resistance, fs in kPa
Shaft friction of P25
estimated
measured
Page 39
Conclusion
16 November 2011
1. The Design Brief for bored pile foundation to the 2nd
Penang Bridge was based on Malaysian practice which
is an empirical approach on the basis of the British
Standard BS8004 (1985).
2. The geotechnical parameters for bored pile foundation
design were verified by in-situ loading test on an
instrumented trial pile.
3. The test was carried out by O-cell method on the trial
pile, 2~ 2.3 m in diameter, 115 m in length including a
socketted depth of 4.3m in sound granite (Grade III/II)
bed rock.
Page 40
16 November 2011
4. The measured shaft friction was less than the estimated
probably because of –
• the influence of direction of loading (uplift) which
worked against the overburden thus leading to a
reduction of shaft friction; and
• the long construction time that might have led to
softening of the soil around the pile shaft
• The slurry cake might not be completely removed by
the concreting
5. The ultimate rock socket friction is 798 kPa under uplift
conditions whereas the maximum rock socket friction in
compression is 941 kPa.
Page 41
6. It is noted from the test result that the ending bearing
capacity was only slightly mobilised. The load carrying
capacity of the test bored pile can be significantly
increased if the end bearing capacity of the pile is
considered.
16 November 2011 Page 42
Thank You
16 November 2011 Page 43
