Design and Construction of Bored Pile Foundation

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Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

1
Design & Construction of Bored Pile Foundation

Ir. Tan Yean Chin & Chow Chee Meng
Gue & Partners Sdn Bhd


ABSTRACT: This paper presents some aspect of design and construction of
bored pile foundation in Malaysia. Empirical equations correlating the value of
the ultimate shaft resistance (f
su
) and the ultimate base resistance (f
bu
) to
SPT’N’ values are suggested as design of bored piles under axial compression
in Malaysia is usually based on the Standard Penetration Tests (SPT), which is
extensively carried out at site. Some aspects of design and construction in
difficult ground conditions such as limestone areas and soft ground are
presented together with some suggestions on quality control for bored pile
construction.

1.0 Introduction

Bored piles are commonly used in Malaysia as foundation to support heavily loaded
structures such as high-rise buildings and bridges in view of its low noise, low vibration, and
flexibility of sizes to suit different loading conditions and subsoil conditions. Such attributes
are especially favoured in urban areas where strict restrictions with regards to noise and
vibration are imposed by relevant authorities which restricted the use of other conventional
piling system, e.g. driven piles. This paper presents a summary of design methodologies
commonly adopted in Malaysia for bored piles under axial compression together with a brief
discussion on the construction aspects of bored piles.


2.0 Geotechnical Capacity of Bored Piles

2.1 Factor of Safety

The Factors of Safety (FOS) normally used in static evaluation of bored pile geotechnical
capacity are partial FOS on shaft (F
s
) and base (F
b
) respectively; and global FOS (F
g
) on
total capacity. The lower geotechnical capacity obtained from both methods is adopted as
allowable geotechnical capacity

Q
ag
=
b
bu
s
su
F
Q
F
Q
+ (eq.1)

Q
ag
=
g
bu su
F
Q Q +
(eq.2)
Note: Use the lower of Q
ag
obtained from eq. 1 and eq. 2 above.

Where:
Q
ag
= Allowable geotechnical capacity (have not included down-drag force, if any)
Q
su
= Ultimate shaft capacity =

i
(f
su
x A
S
)
i = Number of soil layers
Q
bu
= Ultimate base capacity =f
bu
A
b

f
s
= Unit shaft resistance for each layer of embedded soil
f
b
= Unit base resistance for the bearing layer of soil
A
s
= Pile shaft area
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

2
A
b
= Pile base area
F
s
= Partial Factor of Safety for Shaft Resistance =1.5
F
b
= Partial Factor of Safety for Base Resistance >3.0
F
g
= Global Factor of Safety for Total Resistance (Base +Shaft) =2.0

In general, the contribution of base resistance in bored piles shall be ignored due to difficulty
of proper base cleaning especially in wet hole (with drilling fluid). The contribution of base
resistance can only be used if it is constructed in dry hole, proper inspection of the base can
be carried out or base grouting is implemented.


2.2 Design of Geotechnical Capacity in Soil

The design of bored pile geotechnical capacity commonly used can be divided into two
major categories namely:
a) Semi-empirical Method
b) Simplified Soil Mechanics Method


2.2.1 Semi-empirical Method

Bored piles are constructed in tropical residual soils that generally have complex soil
characteristics. The complexity of these founding medium with significant changes in ground
properties over short distance and friable nature of the materials make undisturbed sampling
and laboratory strength and stiffness testing of the material difficult. Furthermore current
theoretically based formulae also do not consider the effects of soil disturbance, stress relief
and partial reestablishment of ground stresses that occur during the construction of bored
piles; therefore, the sophistication involved in using such formulae may not be necessary.

Semi-empirical correlations have been extensively developed relating both shaft resistance
and base resistance of bored piles to N-values from Standard Penetration Tests (SPT’N’
values). In the correlations established, the SPT’N’ values generally refer to uncorrected
values before pile installation.

The commonly used correlations for bored piles are as follows:

f
su
=K
su
x SPT’N’ (in kPa)

f
bu
=K
bu
x SPT’N’ (in kPa)
Where:
K
su
= Ultimate shaft resistance factor
K
bu
= Ultimate base resistance factor
SPT’N’ = Standard Penetration Tests blow counts (blows/300mm)

For shaft resistance, Tan et al. (1998), from the results of 13 nos. of fully instrumented bored
piles in residual soils, presents K
su
of 2.6 but limiting the f
su
values to 200kPa. Toh et al.
(1989) also reported that the average K
su
obtained varies from 5 at SPT’N’ 20 to as low as
1.5 at SPT’N’=220. Chang & Broms (1991) suggests that K
su
of 2 for bored piles in residual
soils of Singapore with SPT’N’<150.

For base resistance, K
bu
values reported by many researchers varies significantly indicating
difficulty in obtaining proper and consistent base cleaning during construction of bored piles.
It is very dangerous if the base resistance is relied upon when the proper cleaning of the
base cannot be assured. From back-analyses of test piles, Chang & Broms (1991) shows
that K
bu
equals to 30 to 45 and Toh et al. (1989) reports that K
bu
falls between 27 and 60 as
obtained from the two piles that were tested to failure.
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

3

Lower values of K
bu
between 7 and 10 were reported by Tan et al. (1998). The relatively low
K
bu
values are most probably due to soft toe effect which is very much dependent on the
workmanship and pile geometry. This is even more pronouncing in long pile. Furthermore,
a relatively larger base movement is required to mobilise the maximum base resistance as
compared to the displacement needed to fully mobilise shaft resistance. The base
displacement of approximately 5% to 10% of the pile diameter is generally required to
mobilise the ultimate base resistance provided that the base is properly cleaned and
checked.

In view of the large movement required to mobilise the base resistance of bored piles and
difficulty in base cleaning, the authors strongly recommend to ignore the base contribution in
the bored pile design unless proper base cleaning can be assured and verified.


2.2.2 Simplified Soil Mechanics Methods

Generally the simplified soil mechanics methods for bored pile design can be classified into
fine grained soils (e.g. clays, silts) and coarse grained soils (e.g. sands and gravels).

Fine Grained Soils

The ultimate shaft resistance (f
su
) of bored piles in fine grained soils can be estimated based
on the semi-empirical undrained method as follows:

f
su
= α x s
u


Where :
α = adhesion factor
s
u
= undrained shear strength (kPa)

Whitaker & Cooke (1966) reports that the α value lies in the range of 0.3 to 0.6 for stiff over-
consolidated clays, while Tomlinson (1994) and Reese & O’Neill (1988) report α values in
the range of 0.4 to 0.9. The α values for residual soils of Malaysia are also within this range.
Where soft clay is encountered, a preliminary α value of 0.8 to 1.0 is usually adopted
together with the corrected undrained shear strength from the vane shear test. This method
is useful if the bored piles are to be constructed on soft clay near river or at coastal area.
The value of α to be used shall be verified by preliminary pile load test.

In the case where bored piles are subjected to significant variations in stress levels after
installation (e.g. excavation for basement, rise in groundwater table) the use of the effective
stress method is more representative as compared to undrained method. This is because
the effective stress can take account of the effects of effective stress change on the K
se

values to be used. The value of ultimate shaft resistance may be estimated from the
following expression:

f
su
= K
se
x σ
v

x tan φ



Where :
K
se
= Effective Stress Shaft Resistance Factor =[can be assumed as K
o
]
σ
v

= Vertical Effective Stress (kPa)
φ

= Effective Angle of Friction (degree) of fined grained soils.

However, this method is not popular in Malaysia and limited case histories of back-analysed
K
se
values are available for practical usage of the design engineer.

Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

4
Although the theoretical ultimate base resistance for bored pile in fine grained soil can be
related to undrained shear strength as follows;
f
bu
= N
c
x s
u


Where:
N
c
= bearing capacity factor

it is not recommended to include base resistance in the calculation of the bored pile
geotechnical capacity due to difficulty and uncertainty in base cleaning.


Coarse Grained Soils

The ultimate shaft resistance (f
su
) of bored piles in coarse grained soils can be expressed in
terms of effective stresses as follows:

f
su
= β x σ
v


Where:
β = shaft resistance factor for coarse grained soils.

The β values can be obtained from back-analyses of pile load tests. The typical β values of
bored piles in loose sand and dense sand are 0.15 to 0.3 and 0.25 to 0.6 respectively based
on Davies & Chan (1981).

Although the theoretical ultimate base resistance for bored pile in coarse grained soil can be
related to plasticity theories, it is not recommended to be included in the calculation of the
bored pile geotechnical capacity due to difficulty and uncertainty in base cleaning.


2.3 Design of Geotechnical Capacity in Rock

The three major rock formations, namely sedimentary, igneous and metamorphic rocks, are
commonly encountered in Malaysia. When designing structures over these formations using
bored pile, the design approaches could vary significantly depending on the formations and
the local experience established on a particular formation.

In Malaysia, bored pile design in rocks is heavily based on semi-empirical method.
Generally, the design rock socket friction is the function of surface roughness of rock socket,
unconfined compressive strength of intact rock, confining stiffness around the socket in
relation to fractures of rock mass and socket diameter, and the geometry ratio of socket
length-to-diameter. Roughness is important factor in rock socket pile design as it has
significant effect on the normal contact stress at the socket interface during shearing. The
normal contact stress increases due to dilation resulting increase of socket friction. The
level of dilation is mostly governed by the socket roughness. The second factor on the intact
rock strength governs the ability of the irregular asperity of the socket interface transferring
the shear force, otherwise shearing through the irregular asperity will occur due to highly
concentrated shear forces from the socket. The third factor will govern the overall
performance of strength and stiffness of the rock socket in jointed or fractured rock mass
and the last factor is controlled by the profile of socket friction distribution. It is very
complicated to quantify all these aspects in the rock socket pile design. Therefore, based on
the conservative approach and local experience, some semi-empirical methods have
evolved to facilitate the quick socket design with considerations to all these aspects. In most
cases, roughness of socket is qualitatively considered as a result of lacking of systematic
assessing method. Whereas the other three factors can be quantified through strength tests
on the rock cores and point load tests on the recovered fragments, the RQD values of the
core samples and some analytical method on assessing the socket friction distribution. It is
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

5
also customary to perform working load test to verify the rock socket design using such
semi-empirical method. Safety factor of two is the common requirements for rock socket pile
design. Table 1 summarises the typical design socket friction values for various rock
formations in Malaysia.

Table 1 Summary of Rock Socket Friction Design Values
Rock Formation Working Rock Socket Friction* Source
Limestone 300kPa for RQD <25%
600kPa for RQD =25 – 70%
1000kPa for RQD >70%

The above design values are subject to 0.05x
minimum of {q
uc
, f
cu
}whichever is smaller.
Neoh (1998)
Sandstone 0.10×q
uc
Thorne (1977)
Shale 0.05×q
uc
Thorne (1977)
Granite 1000 – 1500kPa for q
uc
>30N/mm
2
-
* Note: Lower range to Grade III and higher range for Grade II or better


Another more systematic approach developed by Rosenberg & J ourneaux (1976), Horvath
(1978) and Williams & Pells (1981) is also used in Malaysia. The following simple
expression is used to compute the rock socket friction with consideration of the strength of
intact rock and the rock mass effect due to discontinuities.

f
s
=α×β×q
uc



Where:
q
uc
is the unconfined compressive strength of intact rock
α is the reduction factor with respect to q
uc
(Figure 1)
β is the reduction factor with respect to the rock mass effect (Figure 2)

Figure 1 Rock Socket Reduction Factor, α, w.r.t. Unconfined Compressive Strength
(after Tomlinson, 1995)
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

6


Figure 2 Rock Socket Reduction Factor, β, w.r.t. Rock Mass Discontinuity
(after Tomlinson, 1995)

During borehole exploration, statistics of q
uc
can be established for different weathering
grade of bedrock and the rock fracture can be assessed through the Rock Quality
Designation on the rock core recovered or by interpretation of pressuremeter modulus in the
rock mass against the elastic modulus of intact rock, which is equivalent to mass factor j,
which is the ratio of elastic modulus of rock mass to that of intact rock, as in Figure 2.
Alternatively, Figure 3 can provide some indications of the modulus ratio of the rock mass.
In the some cases, at very small cost, point load test equipment is used to assess and verify
the rock strength on the recovered rock fragment during bored pile drilling after proper
calibration with borehole results.

Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

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Figure 3 Modulus Ratio Ranges
(after Hobbs,1974)

Due to difficulties on quantification of socket roughness, the effect of roughness has not
been explicitly addressed in the above approach, but rather implicitly included in the α factor
with certain socket construction method. Based on the works by Kulhawy & Phoon (1993),
in which is an extension of the above mentioned model by modifying the friction reduction
factor with respect to different socket roughness as shown in the following expression and
Figure 4, Seidel & Haberfield (1995) have further developed the theoretical methodology and
a computer program, “Rocket” for rock socket design. However, it has not gained wide
acceptance in Malaysia as a result of requiring special measuring equipment for the socket
roughness for the input of the said computer program. Nevertheless, Figure 4 does provide
useful reference on limestone, sandstone, shale, mudstone and clay to account for the
socket roughness. The parameter, ψ, is used to represent the socket roughness.

α =ψ×(q
uc
/2p
a
)
-1/2

Where:
ψ : Indicator of socket roughness
p
a
: Atmospheric pressure for normalisation

Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

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Figure 4 Relation between Socket Roughness, Socket
Reduction Factor and Normalised Rock Strength
(after Kulhawy & Phoon,1993)

It is also important to optimise rock socket design with due consideration of the load transfer
behaviour of the socket. Figure 5 shows the analytical results of the socket load transfer
behaviour for modulus ratio, E
p
/E
r
ranging from 0.25 to 1000. As shown in the figure, it is
obvious that there is really no reason to extend the socket beyond 5 times the pile diameter
for E
p
/E
r
=0.25 (very competent intact rock) as no load will be transferred below this socket
length.


Figure 5 Distribution of Socket Resistance w.r.t. Socket Length and Modulus Ratio
(after Pells & Tuner, 1979)

Sometimes, the borehole is a dry hole and at shallow depth, then base resistance will be
considered if the base cleaning and inspection of the base condition can be carried out.
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

9
Very often, the movement to mobilise the base resistance is few folds higher than that to
mobilise the socket friction despite the ultimate base resistance could be very high. As such,
with consideration of compatibility of the pile movement in mobilising both the socket and
base, appropriate mobilising factors to both the socket and base shall be applied to the
foundation design after verification from the fully instrumented pile load test. Such mobilising
factor shall be at least 3, but finally subjected to verification by instrumented load test prior to
production of working piles if there is large number of piles for value engineering. The
assessment of ultimate end bearing capacity of bored pile in rock can be carried using the
following expression.

Q
ub
=cN
c
+γBN
γ
/2 +γDN
q

Where:
c : Cohesion
B : Pile diameter
D : Depth of pile base below rock surface
γ : Effective density of rock mass
N
c
, N
γ
& N
q
: Bearing capacity factors related to friction angle, φ (Table 2, for circular case,
multipliers of 1.2 & 0.7 shall be applied to N
c
& N
γ
respectively)
N
c
: 2N
φ
1/2
(N
φ
+1)
N
γ
: N
φ
1/2
(N
φ
2
-1)
N
q
: N
φ
2

N
φ
: Tan
2
(45°+φ/2)

Table 2 Typical Friction Angle for Intact Rock (Wyllie, 1991)
Classification Type Friction Angle
Low Friction Schist (with high mica content), Shale 20° - 27°
Medium Friction Sandstone, Siltstone, Gneiss 27° - 34°
High Friction Granite 34° - 40°


If the pile length is significant, the contribution of the shaft resistance in the soil embedment
above the rock socket shall also be considered in the overall pile resistance assessment. In
most cases for rock socket pile, the settlement performance is usually governed by the
elastic shortening of the pile shaft. The socket displacement is usually insignificant.
However, load transfer analyses would provide the overall settlement performance.
Construction method is another important aspect to be considered in the bored pile design
on rock. In Malaysia, there are two most common methods in forming the rock socket,
namely rock coring with rock cutting bits and chiselling by mechanical impact. Both methods
have their own merits and need skilful operator to form a proper rock socket. In general,
rock coring method will form a smoother, but intact, socket surface. Whereas chiselling
method will form relatively rougher socket, but could be more fracture due to disturbance to
the inherent discontinuities in bedrock. Chiselling is usually used as a supplementary
technique in drilling through hard rock.

There are also other inherent problems associated with some of the aforementioned rock
formations such as:

a. Limestone: Existence of erratic karst features will need further consideration in the
foundation pile design. Downgrading of pile capacity for piles founded on these karst
features or install the pile at deeper depth to penetrate these features or treatment to
strengthen them can be considered depending on the cost-benefit analyses of the
viable options. Another problem in limestone formation is the existence of slime
made of very loose sand or soft silty clay immediately above the bedrock, which can
cause frequent cave-in and pose difficulties in cleaning up the rock socket. Chan &
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

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Hong (1985) presented the problems of pile construction over limestone. European
Foundations (1998) presented the problems encountered in pile construction in Kuala
Lumpur limestone. Gue (1999) presented some solutions to overcome the
abovementioned problems and the construction controls.
b. Degradable sedimentary formations: These formations easily subject to rapid
degradation in terms of strength and stiffness as a result of stress relief and
ingression of drilling fluid. Slow progress in drilling operation due to inefficient coring
method or inter-layered hard and soft rocks and delay in concreting the piles are the
usual causes of such softening. The solutions to these problems are to use powerful
drilling equipments and avoid delay in concreting.
c. Granite: Core boulders are common features in this formation. This feature can be
easily observed from the outcrops or along river. Therefore, it is important to identify
proper founding stratum for the foundation piles during the subsurface investigation.
This can be overcome by careful assessment of the weathering profile interpreted
from the deep boring exploratory holes.


2.4 Verification of Bored Piles Capacity

For the verification of bored pile capacity, maintained load test is the normal mean specified
by most practicing engineers. In certain cases where detailed interaction behaviours
between the pile and the foundation formations are of interest to the designer for design
refinement and value engineering, full scale instrumented test pile equipped with multi-level
strain gauges, extensometers and occasionally Osterberg load cell and polyfoam soft toe are
constructed and tested depending the objective of the verification. Conventional static
maintained load test is the most common verification pile test adopted by the design
engineers in Malaysia. Quick maintain load test has also gained wide acceptance for the
test piles in Malaysia. Other indirect tests, such as high strain dynamic pile and statnamic
pile tests, have been occasionally used to verify the design.



























Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

11
3.0 Structural Requirements of Bored Pile

Following are some brief guidelines for structural design of bored piles:

a) Allowable structural capacity of bored piles (BS8004, Clause 7.4.4.3.1)
Allowable structural capacity of bored piles =0.25 x f
cu
x A
c

Where:
f
cu
=concrete cube strength at 28 days (Grade 30 to 35 is most common)
A
c
=cross-sectional area of the pile

b) Cover for reinforcement (BS8004, Clause 2.4.5)
Cover for reinforcement =(40mm +values in Table 3.4, BS8110: Part 1)
For example, bored piles (concrete G35) in non-aggressive soil shall required
minimum cover of (40mm +35mm) =75mm

c) Reinforcement (BS8110: Part 1)
For bored piles in compression only, the structural capacity is derived from the
concrete strength alone and some nominal reinforcement is sometimes provided to
prevent damage during construction. However, for bored piles supporting bridges
where there will be bending moment and shear force acting on the piles, then the
bored piles can be designed like beam. Length of the reinforcement can be curtailed
until the influence depth of the flexural effect. Hanging the steel cage without the lower
supporting steel reinforcements has been successfully carried out. However, for ease
of construction, minimum steels are sometimes provided right to the bottom of the
bored pile to support the upper steel cage during concrete casting.

3.1 Verification of Concrete Quality for Bored Pile (Integrity Tests)

Besides verification of capacity, concrete quality of bored piles is also an important aspect of
design and construction of bored piles. Concreting for bored piles is usually carried out using
tremie (self-compacting) concrete. Some general recommendations on tremie concrete as
given by BS8004: 1986 are summarised below:

a) The concrete should be cohesive, rich in cement (i.e. not less than 400 kg/m
3
)
and of slump not less than 150 mm.
b) The sides of the borehole have to be stable. This may be achieved by
maintaining an adequate head of fluid or by the provision of a temporary casing
of the necessary length.
c) The tremie pipe should be watertight throughout its length and have a hopper
attached at its head by a watertight connection.
d) The tremie pipe should be large enough in relation to the size of aggregate.
For 20 mm aggregate the tremie pipe should be of diameter not less than 150
mm, and for larger aggregate tremie pipes of larger diameter are required.
e) The tremie pipe should be lowered to the bottom of the boreholes allowing
ground water to rise inside it. It is essential to prevent the tremie concrete from
mixing with water in the tremie pipe and to this end a plug or other devise
should be used.
f) The tremie pipe should always be kept full of concrete and should penetrate
well into the concrete in the borehole with an adequate margin of safety
against accidental withdrawal if the pipe is surged to discharge the concrete.
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
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g) The pile should be concreted wholly by tremie and the method of deposition
should not be changed part way up the pile, to prevent the laitance from being
entrapped within the pile.
h) If the time taken to form large piles is likely to be excessive, the use of set
retarding admixtures should be considered, particularly in the case of high
ambient temperatures.
i) All tremie pipe should be scrupulously cleaned before use.
j) When drilling muds such as bentonite suspension are used, the fluid at the pile
base should be checked for contamination before concreting to ensure that it
will be readily displaced by the rising concrete.

BS8004: 1986 also recommends the following slump details for concrete used in bored pile
construction:

Table 3 Slump details for concrete used in bored pile construction
Slump Range Typical conditions of use
mm in
Poured into water-free unlined bore.
Widely spaced reinforcement leaving
ample room for free movement
between bars.
75 to 125 3 to 5
Where reinforcement is not spaced
widely enough to give free movement
between bars. Where cut-off level of
concrete is within casing. Where pile
diameter is less than 600 mm.
100 to 175 4 to 7
Where concrete as placed by tremie
under water or bentonite suspension.
150 to collapse 6 to collapse


Tests normally specified as a mean of quality control for concrete during construction include
low strain dynamic load test (e.g. Pile Integrity Test, PIT) and Sonic Logging Test. This test
is primarily used to detect any concrete defects such as honey-combing, cold joints, cracks,
etc. which may affect the overall performance of the bored pile. Some typical results of
integrity tests are shown in Figure 6 and Figure 7:





















Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

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Figure 6 Typical Results for Sonic Logging Test Showing Defect in Concrete




Concrete Defect
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

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Figure 7 Typical Reflectograms from PIT Test


4.0 Design and Construction of Bored Piles in Difficult Ground Conditions

Design and construction of bored piles in difficult ground conditions such as limestone areas
and soft ground requires careful understanding on the pile performance, geological
conditions and soil mechanics. Design aspects for bored piles in such ground conditions
require careful assessment of geotechnical parameters such as rock skin friction (limestone
area) and soil strength parameters (soft ground). The evaluation of rock skin friction can be
carried out using the methods highlighted in Section 2.2 with due consideration in
determining the true bedrock level. It is important that karstic features such as overhangs,
solution cavities and floaters are not mistaken as bedrock and it is usually required to specify
a more stringent termination criteria of 10m of solid coring into rock in limestone areas during
subsurface investigation using borehole.

Construction of bored piles in limestone areas often requires good collaboration between the
design engineer and the contractor. This is due to the highly variable ground conditions
which require significant input from site personnel and in addition to good geotechnical
design, it is recommended that the “observational approach” to be adopted for bored piles
construction in limestone areas. Such arrangement will enable any unexpected geological
formation and uncertainties to be detected and changes to the design can be made
immediately to ensure a safe and cost effective design. Usually some forms of ground
treatments are carried out prior to the piling works (e.g. compaction grouting) or
modifications are made to the method of construction.
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

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Figure 8 Modified Rock Coring Tool for Bored Pile Construction in Limestone Area

Figure 8 shows a modified rock coring tool used for bored pile construction in limestone
area. Such tool enables the casing to penetrate (reamed into) to the required rock socket
length and thus prevents problems such as collapse of loose soil (slime) surrounding the
bored hole normally associated with construction of rock-socketed piles as illustrated in
Figure 8 below:




















Figure 9 Collapse of Loose Soil (Slime) Surrounding the Bored Hole
Inclined limestone
bedrock
Temporary casing
Collapse of Loose
Soil (Slime)
Rock Socket
Rock
Soil
Soft Toe
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

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Figure 10 Performance of Modified Coring Tool


Figure 10 illustrates the performance of the modified coring tool in preventing the above
problem at the interface between rock and soil by coring through to the required socket
depth together with the casing. Conventional method of construction where the temporary
casing is installed using vibro-hammer is unable to penetrate into the rock layer and thus
causes situation such as those shown in Figure 9.

Design of bored piles in soft ground also presents difficulties in the ability of the excavated
hole to remain open prior to formation of the pile (concreting). For very large bored piles,
base failure of the excavated base may be a problem in soft ground, preventing the piles
from achieving the design toe level or length. Two forms of base failure can manifest, i.e.:

a) Basal heave failure

Such failure is prone to occur in very soft and soft clays and silty clays. This failure
mechanism is analogous to a bearing capacity failure, only in reverse being that
stresses in the ground are relieved instead of increased. There are many methods to
examine the basal heave failure and two of the more popular and simple methods
enabling a quick assessment are the methods given by Bjerrum & Eide, 1956 and
Terzaghi, 1943 as shown in Figure 11. This failure can be prevented by using
suitable drilling fluid to stabilise the hole.












Inclined limestone
bedrock
Temporary casing
No collapse of loose soil
(slime) surrounding the
bored bole
Rock Socket
Rock
Soil
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

17















































Figure 11 Basal Heave Failure Analysis








Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

18
b) Hydraulic failure (Boiling)

For site with high groundwater level in sandy subsoil, a simple check against
hydraulic failure can also be carried out to assess the constructability of the piles in
such conditions. This problem can also be easily solved by using suitable drilling fluid
to balance the hydrostatic pressure. The simple Terzaghi’s method can be used in
this respect as shown below:




















Figure 12 Hydraulic Failure Analysis


5.0 Prediction of Bored Pile Settlement

In order to optimise the design of bored pile, it is important to be able to correctly predict
both bearing capacity and settlement of pile under different loading. In view of this, a simple
load-transfer method (Coyle & Reese, 1966) can be utilised to predict the load-settlement
and load distribution of a pile. However, to obtain reasonably reliable prediction of load-
settlement characteristics of pile using this method will require sufficient good quality
database of load-transfer curves and parameters from fully instrumented test piles tested in
similar ground condition to be available for a better correlation with soil properties and pile
geometry. Tan et al. (1998) suggests load-transfer parameters obtained from the testing of
full-scale instrumented bored piles in residual soil of Malaysia. The necessary correlations
to SPT’N’ values are also reported.




Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

19


5.1 Load Transfer Curves for Shaft

The development of shaft resistance is dependent on the relative settlement between the
subsoil and the pile shaft and can be expressed as follows:

Q
s
=

i
[f
s
(z
s
). A
s
]
Where:
Q
s
= Total Shaft Capacity of the Pile (kN)
f
s
(z
s
) = Unit shaft resistance for each layer of soil with relative displacement of z
s
. (kPa)
i = Number of soil layer.
z
s
= Shaft displacement (mm)
A
s
= Pile shaft area at each soil layer




Figure 13 shows a typical load transfer curve for shaft. Shaft displacement, z
s
is the relative
displacement between the pile/soil interface at the mid-depth of each soil stratum.

Figure 13 Typical Load Transfer Curve for Shaft

Where:
f
sc
= Critical shaft resistance corresponding to critical shaft displacement (kPa)
z
sc
= Critical shaft displacement (mm)
f
su
= Ultimate shaft resistance corresponding to ultimate shaft displacement (kPa)
z
su
= Ultimate shaft displacement (mm)

The measured load transfer curves obtained from 13 nos. of instrumented test piles are
normalised against critical shaft resistance (f
sc
) and critical shaft displacement (z
sc
). The
normalised load transfer curve is shown in Figure 14.
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

20

Figure 14 Normalised Load Transfer Curves for Shaft (after Tan et al., 1998)




The best-fit curve obtained to model the load-displacement characteristic of the shaft
resistance is as follows:

(f
s
/f
sc
) =(z
s
/z
sc
)
1/2
; for (z
s
/z
sc
) <1.0

(f
s
/f
sc
) =1+
50
3
(z
s
/z
sc
) ; for 1.0 <(z
s
/z
sc
) <5.0 ; and

(f
s
/f
sc
) =1.3 ; for (z
s
/z
sc
) >5.0

and
f
sc
=2 x SPT’N’ (kPa) ≤ 150 kPa

z
sc
=can be obtained from Figure 8.

There are many factors that have influence on the value of critical shaft displacement (z
sc
) of
bored pile and they are drilling method (dry or wet), type of drilling fluid, type of soil, spatial
variation of soil properties (stiffness and strength), drilling and concreting duration, drilling
tools and also diameter of piles. Tan et al. (1998) selected two key factors, namely the pile
diameter and soil strength (via SPT’N’ values), that can be easily quantified to evaluate their
relationship with z
sc
and are presented in Figure 15. In general, the critical shaft
displacement increases with the increase of pile diameter or decrease in SPT’N’ values.

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
Normal i sed Shaf t Di spl acement , z
s
/z
sc
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
N
o
r
m
a
l
i
s
e
d

S
h
a
f
t

R
e
s
i
s
t
a
n
c
e
,

f
s

/

f
s
c
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

21
Figure 15 Relationship of z
sc
with pile diameter & SPT’N’ (after Tan et al., 1998)


5.2 Load Transfer Curves for Base

Similar to shaft resistance, the load transfer curves for base can be normalised and
presented in Figure 16.

The best-fit curve obtained to model the load-displacement characteristic of the base
resistance is as follows:

(f
b
/f
bc
) =(z
b
/z
bc
)
2/3

Where:
f
bc
= Critical base resistance corresponding to critical base displacement (kPa)
z
bc
= Critical base displacement (mm)
Note: From the field tests, the f
bc
=f
bu.

f
bc
=(7 to 10) x SPT’N’ (kPa)
z
bc
=5% of pile diameter.

Note: When using the value above, proper base cleaning using cleaning bucket shall be
carried out at site.
N = 10
N = 30
N = 50
N > 100
400 500 600 700 800 900 1000 1100 1200 1300
Diameter of Pile (mm)
0
5
10
15
20
25
30
35
40
C
r
i
t
i
c
a
l

S
h
a
f
t

D
i
s
p
l
a
c
e
m
e
n
t
,

Z
s
c

(
m
m
)
Average SPT'N'
SPT'N' = 0- 10
SPT'N' =10- 20
SPT'N' =20- 30
SPT'N' =30- 40
SPT'N' =40- 50
50 <SPT'N' <100
SPT'N' >100
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

22
Figure 16 Normalised Base Resistance and Displacement (after Tan et al., 1998)


6.0 Conclusions

From the above elaborations, the following conclusions can be drawn for the design and
construction of bored pile in Malaysia:

1. For the design of bored piles in soil, the two common methods, namely semi-
empirical and simplified soil mechanics methods are commonly used to
determine the ultimate pile capacity.
2. For the safety margin of pile capacity, partial safety factor of 1.5 and 3.0 for
shaft and base resistances respectively and global safety factor of 2.0 applied to
overall ultimate pile capacity (sum of ultimate shaft and base resistances) are
used.
3. The use of load transfer method is important to optimise the pile design for value
engineering and also provide settlement performance.
4. For rock socket pile design, design approach and charts with consideration of
socket roughness, rock strength, rock mass stiffness and socket geometry are
presented and discussed.
5. In most scenarios, base resistance of bored pile is usually ignored due to
uncertainties in cleaning. Unless for the case of dry hole and inspection of the
base is possible, then base resistance can be considered with appropriate
mobilising factor.
6. Instrumentation test pile is used for design optimisation and value engineering if
there are sufficient pile points for the project to justify the testing cost.

fb/fbc =(Zb/Zbc)
fb/fbc =(Zb/Zbc)
Suggested Design Line
fb/fbc =(Zb/Zbc)
2/3
1/2
1/3
Vijayvergiya (1977)
Phienwej et al. (1994)
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6
Normalised Base Displacement ( Zb/Zbc)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
N
o
r
m
a
l
i
s
e
d

B
a
s
e

R
e
s
i
s
t
a
n
c
e
,

(
f
b
/
f
b
c
)
Piles
A-2
B-2
C-2
E-1
G-2
G-4
Note: The sample specifications for bored piling, testing of bored piling and checklist for
construction of bored pile are attached in Appendix for further reference. Many other specifications,
checklists and technical papers prepared by Gue & Partners Sdn Bhd can be downloaded from our
website at www.gueandpartners.com.my.
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

23
REFERENCES

Aurora,R.R. & Reese, L.C. (1976), Field Tests of Drilled Shafts in Clay-Shales.
Proceedings of the 9
th
International Conference on Soil Mechanics and
Foundation Engineering, Tokyo, Vol.2, pp.371-376.

British Standard Institution, BS8004 : Code of Practice for Foundations

British Standard Institution, BS8110 : The Structural Use of Concrete

Coyle, H.M. & O’Neill, M.W. (1989), New Design Method for Drilled Shafts from
Common Soil and Rock Tests, Proceedings of the Congress on Foundation
Engineering : Current Principles & Practices, Evanston, Illinois.

Coyle, H.M. & Reese, L.C. (1966), Load Transfer for Axially Loaded Piles in Clay,
ASCE Journal of the Soil Mechanics and Foundation Division, 92(SM2),
pp.1-26.

Chan, S.F. & Hong, L.P. (1985), Pile Foundations in Limestone Areas of
Malaysia. Proc. 8
th
Southeast Asian Geo. Conf, Kuala Lumpur.

Chang, M.F. & Broms, B.B. (1991), Design of Bored Piles in Residual Soils based
on Field-Performance Data, Canadian Geotechnical Journal, Vol.28,
pp.200-209.

Davies, R.V. & Chan, A.K.C. (1981). Pile Design in Hong Kong. Hong Kong
Engineer. Vol. 9, no. 3, pp 21-28.

European Foundations (1998), Looking for the Hard Rock, European Foundations
Spring, pp.22-23.

Fleming, W.G.K., Weltman, A.J ., Randolph, M.F. & Elson, W.K. (1992), “Piling
Engineering”, 2nd Edition, Blackie Academic & Professional, Glasgow, UK.

Gue, S. S. and Tan, Y. C. (1998) "Design and Construction Considerations for
Deep Basement", Special Lecture, Lecture on Design and Construction
Considerations for Deep Basement, The Institution of Engineers, Malaysia,
Northern Branch (Penang), Penang, Malaysia.

Gue, S.S. (1999), Foundations in Limestone Areas of Peninsular Malaysia, Civil
and Environmental Engineering Conference – New Frontiers & Challenges,
Bangkok, Thailand.

Gue, S. S., Tan Y.C. and Liew, S. S. (2003) " A Brief Guide to Design of Bored
Piles under Axial Compression – A Malaysian Approach", Seminar and
Exhibition on Bridge Engineering, Bridge Engineering for Practising
Engineers: A Practical Approach, Association of Consulting Engineers
Malaysia, Kuala Lumpur, Malaysia.

Hobbs, N.B. (1974), Factors affecting the Prediction of Settlement of Structures
on Rock, Proc. of the Conf. on Settlement of Structures, Cambridge:
Pentech Press, pp. 579-610.

Horvath, R.G. (1978), Field Load Test Dataon Concrete to Rock Bond Strength,
University of Toronto, Publication No. 78-07.

Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

24
Kulhawy, F.H. & Phoon, K.K. (1993), Drilled Shaft Side Resistance in Clay Soil to
Rock. Proc. On Conf. on Design and Performance of Deep Foundations :
Piles and Piers in Soil and Soft Rock. Geotechnical Special Publication No.
38. ASCE, pp. 172-183.

Neoh, C. A. (1998), Design & Construction of Pile Foundation in Limestone
Formation, Journal of Institution of Engineers, Malaysia, Vol. 59, No. 1,
pp.23-29.

Pells, P.J .N. & Tuner, R.M. (1979), Elastic Solutions for Design and Analysis of
Rock Socketed Piles, Canadian Geotechnical Journal, Vol. 16, pp. 481-
487.

Phienwej, N., Balakrisnan, E.G. & Balasubramaniam, A.S. (1994), Performance
of Bored Piles in Weathered Meta-Sedimentary Rocks in Kuala Lumpur,
Malaysia, Proceedings Symposia on Geotextiles, Geomembranes and
other Geosynthetics in Ground Improvement/ on Deep Foundations and
Ground Improvement Schemes, Bangkok, Thailand.

Reese, L.C. & O’Neill, M.W. (1988), Drilled Shafts : Construction Procedures and
Design Methods, U.S. Department of Transportation - Federal Highway
Administration (Office of Implementation, Washington, 564p.

Rosenberg, P. & J ourneaux, N.L. (1976), Friction and End Bearing Tests on
Bedrockfor High Capacity Socket Design, Canadian Geotechnical Journal,
13, pp. 324-333.

Rowe, R.K. & Armitage, H.H. (1987), A Design Method for Drilled Piers in Soft
Rock, Canadian Geotechnical Journal, 24. pp. 126-142.

Seidel, J .P. & Haberfield, C.M. (1995), The Axial Capacity of Pile Sockets in Rock
and Hard Soil, Ground Engineering, March, pp. 33-38.

Tan, Y.C., Chen, C.S. & Liew, S.S. (1998) Load Transfer Behaviour of Cast-in-
place Bored Piles in Tropical Residuals Soils, Proceedings of the 13th
Southeast Asian Geotechnical Conferences, Taipei, pp. 563-571.

Toh, C.T., Ooi, T.A., Chiu, H.K., Chee, S.K. & Ting, W.H. (1989), Design
Parameters for Bored Piles in a Weathered Sedimentary Formation,
Proceedings of 12
th
International Conference on Soil Mechanics and
Foundation Engineering, Rio de J aneiro, Vol.2, pp.1073-1078.

Thorne, C.P. (1977), The Allowable Loadings of Foundations on Shale and
Sandstone in the Sidney Region. Part 3. Field Test Results. Paper
presented to Sydney Group of Australia Geomechanics Society, Institute
Engineers Australia.

Tomlinson, M.J . (1994). Pile Design and Construction Practice. 4
th
edn. Spon.

Tomlinson, M.J . (1995). Foundation Design and Construction. 6
th
edn. Longman.

Vijayvergiya, V.N. (1977), Load-Settlement Characteristics of Piles. Proceedings
of Port’77 Conference, Long Beach, California, pp.269-284.

Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

25
Whitaker, T. & Cooke, R.W. (1966). An Investigation of the Shaft and Base
Resistance of Large Bored Piles on London Clay. Proceedings of the
Symposium on Large Bored Piles, London, pp 7-49.

Williams, A.F. & Pells, P.J .N. (1981), Side Resistance Rock Sockets in
Sandstone, Mudstone, and Shale. Canadian Geotechnical Journal, 18, pp.
502-513.

Wyllie, D.C. (1991), Foundation on Rock. 1
st
edn, E&FN Spon.

























Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

26


APPENDIX A
Sample Specification for Bored Piling



















Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

27
SPECIFICATION FOR BORED PILING


1.0 GENERAL

1.1 Works in accordance with Specifications

Piling shall conform in all respects with the principles contained in BS 8004.

Unless otherwise stated, concrete, reinforcement and formwork shall be in accordance with the
requirements in Specification on Concrete for Structures.

In the event that the provisions of other specification clauses cause ambiguity or conflict with the
requirement of this Specification clauses, the latter shall take precedence unless otherwise
approved by the Engineer.


1.2 Setting Out

The Contractor shall be required to employ an approved Licensed Surveyor who will set up the
positions of the piles as shown in the pile layout plans of the detailed design. The Contractor will
be responsible for the accuracy of location and positioning of each pile. Any errors in setting out
and any consequential loss to the Employer will be made good by the Contractor to the
satisfaction of the Engineer.

The Contractor shall preserve the pegs set out by the Surveyor. Should any peg be displaced or
lost it must be replaced by a Licensed Surveyor to the approval of the Engineer. Upon
completion of all piling works, the Contractor shall produce as-built Drawings showing the
positions of all piles as installed. The positions of piles shall be verified by a Licensed Surveyor.


1.3 Tolerances

(a) Position
The pile heads shall be positioned as shown on the Drawings within a maximum
deviation of 75mm in either direction from its design position.

(b) Verticality
For bored cast-in-situ piles, the maximum permitted deviation of the finished pile from
the vertical at any level is 1 in 150. The contractor shall demonstrate to the satisfaction
of Engineer the pile verticality is within the allowable tolerance.

(c) Correction
Should piles be installed outside these tolerances affecting the design of the structure,
the Contractor shall propose remedial design and carry out immediate remedial
measure to the approval of the Engineer.


1.4 Person in Charge

The piling work is to be carried out by full time operators and supervisory staff who must be
experienced in the installation of the proposed type of piles.

The Contractor shall submit to the Engineer for approval, written evidence to show that the
persons who will be engaged in the works have had such experience.





Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

28
1.5 Piling Equipment and Accessories

The equipment and accessories must be capable of safely, speedily and efficiently installing
piles to the design requirements at the project site.

Sufficient units of equipment and accessories must be provided to keep to the agreed
construction schedule.


1.6 Sequence of Installation of Working Piles

The Engineer reserves the absolute right and the Contractor shall recognise such right to direct
the installation of working piles in any sequence the Engineer deems necessary for the
satisfactory completion of the works.


1.7 Forcible Correction Not Permitted

Where piles have not been positioned within the specified limits no method of forcible correction
will be permitted.


1.8 Rejected Piles

Any piling work rejected by the Engineer not truly constructed and installed in accordance with
this Specification shall be replaced or rectified by the Contractor to the approval of the Engineer
and this include reinstallation of piles, and the design and construction of a modified foundation
and also constructing of additional compensation piles.


1.9 Records

A record of all piles installed shall be kept by the Contractor and a copy of the record of the work
done each day shall be given to the Engineer within 24 hours. The form of record shall first be
approved by the Engineer before piling works commence. Any comment by the Engineer shall
be incorporated into the record form.

All unexpected boring or installation conditions shall be noted in the records.

Two (2) bound sets of collated and certified (by the Contractor's P.E.) piling records of all piles
shall be submitted by the Contractor to the Engineer after the completion of the piling works.


2.0 BORED CAST IN-PLACE PILES

2.1 General

The Contractor shall carry out the works in accordance with a method statement which has
been approved by the Engineer. This method statement shall include inter alia length of
temporary casing, details of the constituent materials of any drilling fluid used for stabilisation,
the method of inspection, details of the concrete design mix, concreting method, the minimum
time between the completion of one pile and the commencement of the next, and the pattern of
construction.
Unless otherwise described in the Specifications, reinforcement and concrete shall comply with
the requirements in Specification on Concrete for Structures. The Contractor shall ensure that
damage does not occur to completed piles through his method of working. The Contractor shall
submit to the Engineer a pile installation programme. The proposed sequence and timing of pile
installation shall be such that the installation works shall not cause any damage to adjacent
piles. Piling works shall not commence until approval of the Engineer has been obtained. No
bored pile excavation shall commence within 8m of any concreted pile which has not attained
the age of 24 hours.

Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

29

2.2 Tolerances

Tolerances shall be in accordance with the requirements in Clause 1.3 herein.


2.3 Concrete

(a) Trial Mix

The Contractor shall arrange to have a trial mix in the presence of the Engineer prior to
the commencement of field work. The trial mix shall be carried out in accordance to the
design mix submitted to the Engineer.

(b) Concrete for Piles

Unless otherwise stated, concrete used shall comply with Specification on Concrete for
Structures and as approved by the Engineer. The grade of concrete shall be 35
(characteristic strength of 35 N/mm
2
at 28 days) with minimum cement content of 400kg
per cubic meter of concrete. Concrete admixture shall only be used with the permission
of the Engineer, and shall be used strictly in accordance with Specification on Concrete
for Structures.

The Engineer may permit the use of ready mixed concrete provided complete details of
the mix proportions and workability have been submitted to him for prior approval. Such
permission shall only be given for as long as the Engineer is satisfied that the concrete
complies with Specification on Concrete for Structures and the recommendations of
M.S. 523. The Contractor shall ensure that the Engineer shall have access to the
supplier's mixing plant at all times for inspection and checks on quality of concrete
supplied. Each load shall be accompanied by a delivery note stamped with the time of
mixing and stating the consignee and quantities of each material in the mix including
water and additives.

(c) Concrete Testing

Close control of the mixing of the concrete shall be exercised and cube strength tests
shall be carried out in accordance with M.S. 26. Unless the Engineer otherwise directs,
a set of at least three 6" cubes shall be taken for every 10 cubic metres or every group
of 10 batches of concrete used for the piling works. For the latter, the samples shall be
taken from one single batch randomly selected from the group of batches. One cube of
each set shall be tested at seven days and the remaining two at 28 days after casting.
The test cubes shall be made from a representative batch of concrete as that used for
the piling works and each cube shall be properly marked and identified with details
relating the specimen to the borehole in which the concrete is used.

Test shall be carried out by approved lab. Test results shall be submitted to the
Engineer within 48 hours after testing.

The Contractor shall not carry out the specified cube strength tests without prior notice
to the Engineer. The tests must be witness by the Engineer or his representative. The
contractor shall provide sufficient quantity of all necessary equipment at site to carry out
these tests.

(d) Workability

Slump test shall be undertaken for every truck load of concrete. Slump measured at
the time of discharge into pile shaft or at the time of discharge into the concrete pump
hopper shall be in accordance with the standards shown below unless otherwise
approved. A concrete pump shall not be used to place tremie concrete directly into the
pile shaft.


Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

30
Class of Slump (mm) Typical Conditions of Use
Workability

A 100 ± 25 Where concrete is to be placed in
water-free shaft.

B 175 ± 25 Where concrete is to be placed by
tremie method under drilling fluid.

The concrete for piles shall be as specified in the design requirement with suitably
enriched cement content to permit a high slump mix. Alternatively, the Contractor may
incorporate an approved set retarding additive into the mix to ensure extended
workability of the concrete after placement. It is held that the Contractor has included
these provisions in the unit rate for the pile.

(e) Failure of Concrete Cube Tests

If the concrete cubes as tested failed to satisfy the criteria as prescribed in
Specification, the Contractor shall undertake all necessary additional and consequential
remedial/compensatory Work to the approval of the Engineer. The piles shall be
rejected as in Clause 1.8 "Rejected Piles".


2.4 Pile Excavation

(a) Pile size and length

The Contractor shall carry out own tests along the proposed wall alignment to
determine the bedrock level. Probing of bedrock shall be carried out along the
proposed wall line at intervals to be agreed by the Engineer.

(b) Boring near recently Cast Piles

Piles shall not be bored next to other piles which have recently been cast less than 24
hours or contain unset concrete, whichever longer to avoid damage to any of these
piles.

(c) Stability of Boreholes

It is held that the Contractor has allowed in the unit rate of the pile for the
implementation of all necessary measures, including the provision of all materials,
labour and plant, for maintaining the stability of the sides of boreholes during bored pile
installation and successful completion of the piles. The Contractor shall submit his
proposed methods for agreement prior to commencement of boring operations.

Irrespective of the presence of ground water, the sides of all borehole shall be kept
intact and no loose material shall be permitted to fall into the bottom of the boreholes.
The Contractor's boring equipment shall be able to sink a steel casing to support the
sides of all boring.

If the sides of boreholes are found to be not stable, temporary steel casing shall be
driven into stable stratum. The borehole shall be filled with drilling fluid to a level
sufficiently to stabilise the boreholes.

If ground water is found in any hole in sufficient quantity or gushing out as to affect
boring operations or excavations and removal of soil from the boreholes, or the sides of
boreholes collapse, then a steel casing of appropriate size and length in conjunction
with stabilising fluid or other alternatives of sufficient strength shall be used to support
the sides of the borehole and permit boring operations to proceed smoothly and safely.
The proposed drilling fluid mix must be submitted to the Engineer for approval.

Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

31
Excavations shall not be exposed to the atmosphere longer than is necessary and shall
be covered at all times when work is not in progress. Pile excavated shall be casted
within 24 hours unless otherwise agreed by the Engineer.

In the event of a rapid loss of drilling fluid from the borehole excavation and caused
instability of bore, the excavation shall be backfilled without delay or other appropriate
and approved remedial measures taken by the Contractor like installing temporary
casing prior to resuming boring at that location.

(d) Stability of bore by temporary casing method

Where the use of a temporary casing is required to maintain the stability of a bore, the
bottom of casing shall be kept a minimum of 1 metre or more below the unstable strata
to prevent the inflow of soil and the formation of cavities in the surrounding ground.

Temporary casings shall be thin walled mild steel cylindrical casing, spirally welded or
other similar construction. The dimensions and quality of the casing shall be adequate
to withstand without damage or distortion all handling, construction and ground stresses
to which they will be subjected, including preventing concrete from within the pile from
displacing soft soil or soil squeezing in and displacing fresh concrete. The casings shall
have an internal diameter not less than the specified pile diameter. They shall be free
of significant distortion, of uniform cross-section throughout each continuous length and
free from internal projections and encrusted concrete which might prevent the proper
formation of piles. The joints of casings shall be reasonably watertight.

If temporary casings are damaged during installation in a manner which prevents the
proper formation of the pile, such casings shall be withdrawn from the bore before
concrete is placed, repaired if necessary, or other action taken as may be approved to
continue the construction of the pile.

(e) Rock Coring

Rock coring shall means coring of sound bedrock using a coring bucket or approved
method. The used of chisel shall not be permitted. Coring of rock other than two items
specified below shall not be considered as coring in rock, and will only be considered
as boring in soil.

(i) Rock socket length
(ii) Cavity roof (in limestone formation)

Coring of inclined rock surface, limestone pinnacles, cavities and soil below
boulder/floater shall be considered as boring in soils.

Socket length shall be measured from the flattened horizontal bedrock surface. This
flat horizontal surface shall be probed using kelly bar or steel bar at a minimum of five
positions over the borehole to confirm sound bedrock for socketing.

(f) Spillage and Disposal

All reasonable steps shall be taken to prevent the spillage of drilling fluid on the site in
areas outside the immediate vicinity of boring. Discarded drilling fluid shall be removed
from the site without delay. In disposal of unwanted drilling fluid, the Contractor shall
comply with government regulations and shall propose a proper disposal method to be
approved by the Engineer.

(g) Inspection of Pile Excavation

Where practicable, all pile excavations shall be inspected for their full length before
concreting. The Contractor shall provide all the apparatus necessary for the inspection.

Inspection shall be carried out either from the ground level or below ground level at the
sole discretion of the Engineer prior to concrete being placed in the borehole. For such
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inspection to be carried out safely, the Contractor shall provide all facilities and
assistance to enable the said inspection to be done. In the course of inspection any
loose or soft material in the borehole which is likely to affect the performance of the pile
shall be removed to the satisfaction of the Engineer.

In the case of inspection from ground level, the base of the boring shall be inspected by
approved method for wet hole and means of a light for dry hole to ensure that all loose,
disturbed and/or remoulded soil is removed and that the sides of the boring will remain
stable during the subsequent concreting operations. The verticality and position of the
boring shall be checked to ensure that they meet the specified tolerances.

Inspection below ground level shall be carried out for piles with shafts of 760mm (2'6")
diameter and above. For this purpose the Contractor shall, apart from providing other
safety measures, also provide the required facilities such as an approved type of a steel
safety cage with an air-line, lifting cable and hoist, gas detector, lights, etc. to enable
descent into and ascent from the borehole to be carried out safely without any danger
to life. In this regard the safety precautions described in CP 2011:1969 "Safety
Precautions in the Construction of Large Diameter Boreholes for Piling and Other
Purposes" shall generally be followed, unless otherwise directed by the Engineer.

(h) Pumping from Bored Hole

Pumping from boreholes may be carried out from time to time on a number of piles
designated by the Engineer to verify the suitability of dry hole construction, or to
investigate and rectify a cold joint in a pile shaft where concreting has been interrupted.

No pumping from a borehole shall be permitted unless a casing has been placed into
the stable stratum which prevents further ingress of water of significant quantity from
other strata into the borehole, or unless it can be shown that pumping will not have a
detrimental effect on the surrounding soil or hamper the piling operation in any way.

(i) Cleaning Out

Upon completion of boring the excavation shall be cleaned of all loose, disturbed and or
remoulded soil and sediment soil to expose a firm base of undisturbed material using a
suitable and effective method to be approved by the Engineer.

(j) Continuity of Construction

A pile constructed in a stable soil without the use of temporary casing or other support
shall be bored and concreted without prolonged delay to ensure that the soil
characteristics are not significantly altered.

(k) Surface Water

All boreholes shall be protected from the possibility of any surface water entering the
hole from time to time and until the hole is completed and ready to be concreted.

(l) Excavation Materials

Surplus earth resulting from piling operations shall be used where required or removed
from site as directed by the Engineer.


2.5 Placement of Reinforcement

Reinforcement shall be free from rust and mud and not be placed until inspected and accepted.

Reinforcement cages shall be sufficiently rigid to ensure that they remain at their correct level
during the lifting and placing of the concrete and the extraction of temporary lining tubes.

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Reinforcement shall be maintained in its correct position during concreting of the pile. The
minimum cover to all reinforcement shall not be less than 75mm.

Concrete spacer shall be provided at every 3m interval, size and minimum yield strength of
reinforcement shall be as specified in the Drawing. Details by which the Contractor plans to
ensure the correct cover to and position of the reinforcement shall be approved by the Engineer.

The main longitudinal reinforcing bars in piles not exceeding 12 metres in length shall be in one
continuous length unless otherwise specified. In piles longer than 12 metres and required to be
reinforced throughout their full lengths when specified, joints with staggered laps of alternate
bars will be permitted in main longitudinal bars at 12- metre nominal intervals unless otherwise
specified in the Drawings. Joints in reinforcement shall comply with the specific requirements of
BS8110 clause 3.12.8.

The Contractor shall submit for approval a method statement on the manner by which he
intends to lower reinforcement cages into pile shafts. Where tack welding is carried out on pile
reinforcement for the purpose of hoisting, such welding shall be located only within the top
100mm of each reinforcement cage. Where the top of a reinforcement cage being lowered is to
be lapped to the next cage, as in the case of tension piles exceeding 12 metres in length, the
Contractor shall provide adequate sacrificial steel to compensate any lapped reinforcement
which has been tack welded, where such tack welding is the requirement of the Contractor for
his hoisting operation. Sacrificial steel shall be of the same grade and size as that of the
compensated bar.

If required by the Engineer, reinforcement cages shall be flushed with fresh water to remove
accumulated salts or other deposits immediately prior to lowering into the pile shaft.


2.6 Concreting in Wet Hole

Immediately after the boring for the pile has been completed, approval to commence concreting
shall be sought and, when this has been obtained, concreting shall start forthwith and continue
without interruption. All concrete for cast-in-place piles shall be compacted to produce a dense
homogeneous mass by a method agreed by the Engineer.

Concrete to be placed under drilling fluid shall placed using a tremie concrete pipe in
accordance with BS 8004, Clauses 7.4.5.4.2 and 8.2.2.3.4. Where discrepancies arise, the
provisions of this specification shall take precedence.

Alternative methods of placing concrete such as the use of a drop bottom bucket or hose from a
concrete pump will not be accepted by the Engineer. At no stage concrete be permitted to
discharge freely into drilling fluid.

Before placing concrete, agreed measures shall be taken by the Contractor to ensure that there
is no accumulation of contaminated drilling fluid, silt or other deleterious material at the base of
the bore. Contaminated drilling fluid could impair the free flow of concrete from the tremie pipe
and affecting the performance of the pile.

A sample of the drilling fluid shall be taken from the base of bore using an accepted sampling
device. If the drilling fluid does not comply to the specification, concrete placement shall not
proceed and the Contractor shall modify or replace the drilling fluid to meet the requirements of
this specification.

The tremie concrete pipe shall consist of a series of metal pipes with internal diameter not less
than 250mm. The receiving hopper shall have a capacity at least equal to that of the pipe it
feeds. At all times, a sufficient quantity of concrete shall be maintained within the pipe to ensure
that the pressure from concrete exceeds that from the water or drilling fluid.

The hopper and pipe of the tremie shall be clean and watertight throughout. The pipe shall
extend to the base of the bore and a sliding plug or barrier placed at the discharge outlet of the
pipe to prevent direct contact between the first charge of concrete in the tremie pipe and drilling
fluid. If the plug or barrier is sacrificial, it shall not be retained in the mass of the concrete.
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The tremie pipe outlet shall be kept at least 1.5 metres below the surface of the concrete at all
stages in the pour. The Contractor shall develop a system of level checks for the concrete and
pipe outlet to ensure that this requirement is met. The tremie pipe shall be withdrawn upward
gently behind the concrete level, and shall not be given any violent movement either in
dislodging the concrete within the pipe or for any other reason.

Concrete placement shall be halted should a delay or breakdown occur during the concreting
operation which in the opinion of the Engineer, could cause a cold joint, entrapment of latency in
the tremie concrete, or otherwise lead to defective concrete. Before the remainder of the pile
shaft can be concreted, the pile shall be dewatered and the top surface of the tremie concrete
cut back to sound concrete and cleaned of all laitance and weak concrete. The remainder of
the pile shall either be cast by tremie or in the dry, as directed by the Engineer. If this remedial
work can not be carried out due to construction difficulty, the Contractor will need to construct a
replacement pile.

The concrete for each pile shall be from the same source. The Contractor is to ensure that the
supply from whatever source (whether site-mixed or ready-mixed) is of sufficient quantity so that
concrete for each pile shall be placed without such interruption.

All holes bored shall be concreted within the same day. In the event of rain, the Contractor is to
provide adequate shelter to keep the hole dry and to concrete under cover.

The method of placing and the workability of concrete shall be such that a continuous monolithic
concrete shaft of the full cross-section is formed. The method of placing shall be approved by
the Engineer. The Contractor shall take all precautions in the design of the mix and the
placement of concrete to avoid arching of the concrete in the pile shaft. No spoil, liquid or other
deleterious matter shall be allowed to contaminate the concrete.

Temporary casings shall be extracted while the concrete within remains sufficiently workable to
ensure that the concrete is not lifted and that the resultant pile is continuous and of full section.
Temporary casings shall be extracted in not more than 2 hours after concreting has completed.

When casings and linings are withdrawn as concreting proceeds, a sufficient head of concrete
shall be maintained to prevent the entry of ground water which may cause reduction of
cross-section of the pile. No concrete shall be placed after the bottom of the casing or lining has
been lifted above the top of the concrete. Concrete shall be placed continuously as the casing
is extracted until the desire head of concrete is obtained.

Adequate precautions shall be taken in all cases where the withdrawal of casing could result in
excess heads of water or drilling fluid. Excess pressure heads are caused by the displacement
of water or fluid by concrete as the concrete flows into its final position against the wall of the
shaft. Precautions such as the use of two or more discontinuous lengths of casing (double
casing) shall be deemed an acceptable method of construction in this case.

In the event of the ground water level being higher than the required pile head cut-off level
shown in the contract drawings, the Contractor shall submit his proposals for agreement prior to
placing concrete. The pile head shall not be let below the ground water level unless adequate
and agreed precautions are taken.

The top of the pile shall be brought above the required cut-off level by an amount sufficient to
ensure a sound concrete at cut-off level and the surplus removed to ensure satisfactory bonding
of the pile head to the structure.

The actual volume of concrete used for each pile must be measured with the calculated volume
required. If the difference between these two volumes indicates a possible necking, the
Contractor shall propose and carry out appropriate tests and measures to the approval of the
Engineer to ensure the adequacy of the pile.

Backfilling of Empty Bore - On completion of concreting, the remaining empty bore shall be
backfilled with sand or lean concrete unless otherwise agreed by the Engineer.

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Any consequences causing the pile rejected by the Engineer due to supply of concrete shall be
on contractor's own risk.


2.7 Stripping Pile Heads and Bonding

The piles shall be constructed to a sufficient height above the required cut-off levels (‘overcast’)
to ensure that all concrete at and below cut-off level is homogeneous and free of laitance and
deleterious matter. The Contractor shall be required to provide adequate reinforcement with
sufficient length to project above cut-off levels so that the reinforcement can be properly bonded
in the capping beam. After completion of piling, the Contractor shall excavate and cut back the
piles as necessary to verify the cut-off levels and to give accurate details of the pile positions as
compared with the positions indicated on the pile layout plans of the detailed design. Defective
concrete in pile heads shall be cut away and made good with new concrete well bonded to the
pile head. If the pile is undercast, it shall be built-up with new concrete and a permanent casing.


2.8 Drilling Fluid and Soil Tests

Minimum frequency of testing are as follows:
1) fresh drilling fluid
2) drilling fluid taken from the bottom of the pile before concreting
3) recycle drilling fluid taken from desanding machine
4) drilling fluid left in the bored hole for more than 12 hours

The frequency of testing drilling fluid and the method and procedure of sampling shall be
proposed by the Contractor and agreed by the Engineer before the commencement of the work.
The frequency may subsequently be varied with the approval of the Engineer. Control tests for
density shall be carried out daily on the drilling fluid using suitable apparatus. The measuring
device shall be calibrated to read within 0.01 g/ml. The results shall be within the ranges stated
in Table 2.1.

All reasonable steps shall be taken to prevent the spillage of drilling fluid on the site. Discarded
drilling fluid shall be removed from the site without delay and such removal shall comply with the
regulations of the relevant Authorities.

If sand content more than 5%, Contractor shall carried out desanding to screen out sand from
drilling fluid before concreting.

TABLE 2.1 - TESTS FOR BENTONITE DRILLING FLUIDS

Property to be
measured
Compliance values
measured at 20°C
Test
Method/Apparatus
Density Less than 1.10g/ml Mud Density
Balance
Fluid Loss Less than 40ml 30 minutes test
Viscosity 30-90 seconds
or
less than 20cP
Marsh Cone method

Fann Viscometer
Shear Strength
(10 minutes gel
strength)
1.4 - 10N/m
2

or
4 - 40N/m
2

Shearometer

Fann Viscometer
Sand Content Less than 5% Screen
pH 9.5 – 12

pH indicator paper
Strips or electrical
pH meter

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Note : Where the Fann Viscometer is used, the fluid sample should be screened by 300µm
sieve before testing.

Tests for drilling fluid other than bentonite have to be approved before use.


2.9 Dry Hole Construction (If directed by the Engineer Only)

For the purpose of the tender, the boreholes for pile construction shall be assumed to be wet
holes, where the tremie method of concreting shall be adopted.

However, during pile installation as directed by the Engineer, the Contractor shall be required to
determine for a number of designated piles whether dry hole construction could be
implemented. The accepted method for dry hole verification shall be to pump out all water in
the hole, and observe the rate of water intrusion and to be decided by the Engineer.

Whenever practicable, concrete for bored piles may be placed into a clean, dry hole. All dry
holes shall be inspected and approved by the Engineer prior to placing of concrete. All facilities,
labour and material required for the inspection shall be provided by the Contractor.

Agreed measures shall be taken to avoid segregation and bleeding, and that the concrete at the
bottom of the pile is not deficient in grout. The concrete shall be placed by tremie. The free fall
of the concrete from the bottom of the tube shall not exceed 1.5 times the diameter of the pile.
The concrete shall be placed as quickly as possible where the ground is liable to deteriorate on
exposure.


2.10 Pile Acceptance Criteria

The target termination depth, required socket length, concrete strength and the required
working pile capacities are as shown in the drawings. The actual termination depths and socket
lengths shall be agreed with the Engineer based on review of the conditions encountered during
boring and prior to commencement of concreting. Piles shall meet tolerance requirements as
specified in Clause 1.3 and satisfying integrity tests as specified in Clause 3.0.


2.11 Casting Level

Concrete shall be finished not less than 300mm above the cut-off level (‘overcast’) to ensure
that all concrete at and below cut-off level is homogeneous and free of laitance and deleterious
matter. A thicker overcast may be required by the Engineer depending on site condition, and
this shall be carried out. The overcast shall be chipped off to cut-off level later by the
Contractor.


2.12 Defective Concrete

Defective concrete in the pile heads shall be cut away and made good with new concrete well
bonded into the old concrete.


2.13 Piling Records

Submission of the record shall be in accordance with Clause 1.9 herein.

The record shall contain all information required by the Engineer including the following:

- Name of Supervisor
- Pile forming equipment including Rig No.
- Length, diameter and reference number of the borehole
- Existing ground level
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- Cut-off level, rock level, pile toe level
- Length of pile
- Log of material encountered and level of change in strata and where boring stops
- Speed of boring through soil or rock shall be recorded for every metre of drilling
- Depth bored and details of inclination or displacement of the pile during boring and date
of inspection
- Length of reinforcement cage, reinforcement details
- Water table below ground level
- Levels where seepage occurs
- Results of tests on soils
- Results of tests on concrete cubes (slump test)
- Length of temporary casing if used
- Date and actual volume of concrete placed in piles, time start and complete
- Concrete level after each truck of concrete
- Details of all inspections
- Details of all obstructions, delays and other interruption
- Signature of the Resident Engineer or his representative
- Weather condition
- Method of casting (wet/dry tremie)
- Date and time boring start and complete and speed of drilling
- Type of stabilising fluid
- Collapse of bore or loss of drilling fluid
- Cavities or slump zones encountered


2.14 Treatment of Cavities and Slump Zones

The specification for treatment of cavities and slump zones should be followed unless otherwise
instructed by the Engineer.


3.0 INTEGRITY TESTING OF PILES

3.1 General

Piles shall be selected by the Engineer for testing and detection of major faults, necking,
discontinuities, and cross sectional areas of the piles. Integrity testing of piles shall be carried
out by an independent testing organisation approved by the Engineer.

If the results of the tests show that the pile or piles are defective, the pile or piles shall be treated
as faulty and shall be rejected unless the Contractor can demonstrate to the approval of the
Engineer effective remedial measures that will be carried out.

The results of tests shall be printed out immediately during tests with printer facility at site and
submit to Engineer at site. The Engineer's interpretations and conclusions arrived at on the test
results shall be final.

Working piles shall be subjected to shock method and sonic logging tests.


3.2 Shock Method

(a) Preparation of the Pile Head

The pile head shall be clearly exposed, free from debris, etc. and not more than 1.0
metre above or below ground level, otherwise the surrounding soil shall be built up or
excavated to meet this condition. The pile head shall be smooth over its complete
cross-section, free from irregularities and perpendicular to the vertical axis of the pile.

The pile head shall consist of sound concrete. This shall be achieved during the
concreting of the pile by flushing out all weak mortar, etc. from the top of the pile head
and carefully screeding off to provide a smooth level surface in sound concrete.
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Alternatively, if the pile head is prepared after concreting, all weak mortar, broken
concrete, etc. shall be removed from the pile head to expose sound concrete over its
complete cross-section. After cleaning it off to ensure a sound bond, a very thin screed
(maximum 1cm) of strong sand/cement mortar, rapid hardening compound, shall be
spread to provide a smooth working surface for the shock test equipment. The mortar
shall be allowed to harden before testing.

Any reinforcement or other inclusions protruding from the pile head shall not prevent
the testing team from giving the pile the required impact force over the centre of the pile
and the placing of a 5cm diameter (approx.) electronic pick-up at about 10cm from the
periphery of the pile. Access shall be provided for the service van within 30 metres of
the pile.

(b) Shock Test Equipment

The shock which is to be imparted onto the pile head shall be carried out using a
suitable hammer or any approved method which is capable of transmitting vibration to
the base of the pile shaft. The electronic pick-ups located on the pile head shall be
approved velocity transducers or accelerometers connected through an approved
frequency analyser to a X-Y plotter. The mechanical admittance shall be plotted on a
vertical scale and the frequency on the horizontal scale. Both the horizontal and vertical
scales shall be varied as required. The equipment shall have an independent power
supply.

(c) Shock Test

The Contractor shall provide the qualified and experienced testing team with a site plan
showing the pile layout and a list of the piles to be tested.

Before testing, the heads of the piles shall be inspected by the testing team for
regularity and soundness and any unsatisfactory pile heads shall be reported to the
Engineer. They shall be made good to the satisfaction of the Engineer and smoothed
off using a suitable epoxy mortar if necessary. Preliminary tests shall be carried out to
establish the appropriate scales and to check the electronic circuit.


3.3 Sonic Logging Method

For the purpose of carrying out sonic logging, the Contractor shall be required to install the
necessary tubing for the tests at all pile locations or as directed by the Engineer.

The tubes shall be of internal diameter not less than 50mm with no internal projections or
couplings. They can be of mild steel pipes. Four (4) nos. of tubes are required for each pile
greater than 700mm diameter while two (2) nos. are required for each smaller diameter pile.

The tubes shall be fixed to the longitudinal bars with equal spacing on the inside perimeter of
the links. The tubes shall be watertight with the bottom of the tube sealed and suitably weighted
to prevent floating. The tubes shall be secured to the internal face of the reinforcement cage at
equal distance from each other on the circumference.

The tubes shall extend the full depth of the pile and project 300mm above the top of the
concrete and not lower than 300mm below the surface of the ground. All joints shall be made
watertight. The tubes shall be filled with water to provide the necessary acoustic coupling, and
then plugged or capped before concreting. The type of tube and condition of sealing shall be
checked and approved by the Engineer before installation.

The rate of logging for increments of depth shall be approved by the Engineer.

After conducting the tests, all tubes shall be grouted with approved strength and water in the
tubes displaced. The grout shall be dense cement grout with an approved expanding agent.

Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
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Prior to testing, the necessary equipment shall be thoroughly checked to ensure that all parts
are functioning satisfactorily. During sonic logging testing, where any irregularities are detected,
the tests shall be repeated at a smaller scale to allow a ‘close-up view’ of the irregularities.


Presentation of Test Results

The time required to carry out the test for each pile must be recorded along with records of
starting time and finishing time.

The results of the tests shall be presented in report by the testing firm and must be signed by a
professional engineer. The report shall include comprehensive engineering analysis of the test
results for each pile taking into consideration the soil condition and any other relevant factors.
Interim reports of each pile or group of piles tested in one day shall be submitted to the
Engineer within 2 days of the completion of the test or tests. A final comprehensive report shall
be submitted to the Engineer within 7 days of the completion of the last test or tests.


3.4 Proof Coring of Pile Shafts

The Contractor shall check the quality of the concrete in the shafts of working piles as directed
by the Engineer. This shall be achieved by a vertical diamond core hole drilled through the
centre region of the pile from pile head to required depth. The location of the drill hole and
depth shall be approved by the Engineer. Full core recovery shall be attempted. The core so
produced shall not be less than 50mm in diameter. The minimum number of piles for proof
coring test shall not be less than 1% of the total number of working piles or as specified in the
Bill of Quantities.

For each pile to be cored, the coring work shall be completed before the concrete in the pile has
reached an age of 28 days to allow the cores to be tested for unconfined compression tests at
28 days. The Engineer shall mark the sections of the core to be tested and the Contractor shall
arrange for testing in an approved laboratory. A minimum of six(6) unconfined compression
tests shall be conducted on cores obtained from a pile. Additional number of the unconfined
compression tests may be requested by the Engineer if in the opinion of the Engineer the
quality of the concrete of the pile is doubtful.

The cored hole in the pile shall be grouted after testing. The grout shall be an approved dense
cement grout with a minimum 28 days strength of equal or higher than the strength of the
concrete of the bored pile. If the pile is found to be faulty in the opinion of the Engineer because
of defects such as cracks, overbreaks, necking, cavity, inclusion of foreign deleterious materials,
poor quality concrete, etc., the pile shall be rejected and the Contractor shall undertake all
necessary remedial measures to the approval of the Engineer.

In conjunction to core testing, the Engineer may request sonic logging test to be conducted in
the cored holes or pre-installed tubings to determine the in-situ density of the pile and their
integrity continuously along the pile length in correlation with core samples.










Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
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APPENDIX B
Sample Specification for Testing of Bored Piling














Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
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SPECIFICATION FOR TESTING OF BORED PILE


1.0 GENERAL

This specification deals with the testing of bored piles by the application of an axial load or
force. It covers vertical piles tested in compression (i.e. subjected to loads or forces in a
direction such as would cause the pile to penetrate further into the ground) and vertical piles
tested in tension (i.e. subjected to forces in a direction such as would cause the piles to be
extracted from the ground).

This specification also covers high strain dynamic testing of installed piles.


2.0 DEFINITIONS

Compression pile: a pile which is designed to resist an axial force such as would cause it to
penetrate further into the ground.

Tension pile: a pile which is designed to resist an axial force such as would cause it to be
extracted from the ground.

Preliminary pile (for failure load test): a pile installed before the commencement of the main
piling works or specific part of the Works for the purpose of establishing the suitability of the
chosen type of pile and for confirming its design, dimension and bearing capacity as well as
value engineering.

Kentledge: the dead weight used in a loading test.

Reaction system: the arrangement of kentledge, piles, anchors or rafts that provides a
resistance against which the pile is tested.

Maintained load test: a loading test in which each increment of load is held constant either for
a defined period of time or until the rate of movement (settlement or uplift) falls to a specified
value.

Failure load test: a load test applied to a preliminary pile. Maximum test load for this test
should not normally be less than 250% of the estimated working load, but the possibility of
failure load test carried well beyond 300% of the predicted working load should not be ruled
out. This test serves as a design check and refinement for soil parameters used to determine
the lengths of subsequent working piles.

Ultimate bearing capacity: the load at which the resistance of the soil becomes fully mobilized.

Allowable load: the load which may be safely applied to a pile after taking into account its
ultimate bearing capacity, negative skin friction, pile spacing, overall bearing capacity of the
ground below and allowable settlement.

Working load: the load which the pile is designed to carry without exceeding the allowable
settlement requirement.


3.0 SAFETY PRECAUTIONS

3.1 General

When preparing for, conducting and dismantling a pile test, the Contractor shall carry out the
requirements of the various Acts, orders, regulations and other statutory instruments that are
applicable to the work for the provision and maintenance of safe working conditions, and shall
in addition make such other provision as may be necessary to safeguard against any hazards
that are involved in the testing or preparations for testing.
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The Contractor shall be responsible for the design of the reaction system (e.g. kentledge or
reaction piles/ground anchor, etc). The design of the reaction system shall be endorsed by
the Professional Engineers registered with The Board of Engineers, Malaysia (BEM).


3.2 Personnel

All tests shall be carried out only under the direction of an experienced and competent
supervisor conversant with the equipment and test procedure. All personnel operating the
test equipment shall have been trained in its use.


3.3 Kentledge

Where kentledge is used, the Contractor shall construct the foundations for the kentledge and
any cribwork, beams or other supporting structures in such a manner that there will not be
any differential settlement, bending or deflection of an amount that constitutes a hazard to
safety or impairs the efficiency of the operation. The kentledge shall be adequately bonded,
tied or otherwise held together to prevent it from falling apart, or becoming unstable because
of defection of the supports.

The weight of kentledge shall be at least 1.2 times than the maximum test load and if the
weight is estimated from the density and volume of the constituent materials, an adequate
factor of safety against error shall be allowed. The Contractor shall take all reasonable steps
to ensure that sufficient excess load capacity is at all times available for the uninterrupted
execution of a load test.


3.4 Reaction Piles And Ground Anchors

Where tension piles or ground anchors are used (only if specified by the Engineer), the
Contractor shall ensure that the load is correctly transmitted to all the tie rods or bolts. The
extension of rods by welding shall not be permitted unless it is known that the steel will not be
reduced in strength by welding. The bond stresses of the rods in tension shall not exceed
normal permissible bond stresses for the type of steel and grade of concrete used.

The reaction piles or ground anchorages shall be so designed that they will resist the forces
applied to them safely and without excessive deformation which could cause a safety hazard
during the work. Such piles or anchorages shall be placed in the specified positions, and
bars, tendons or links shall be aligned to give a stable reaction in the direction required.


3.5 Testing Equipment

In all cases the Contractor shall ensure that when the hydraulic jack and load measuring
device are mounted on the pile head, the whole system will be stable up to the maximum test
load to be applied. Means shall be provided to enable dial gauges to be read from a position
clear of the kentledge stack or test frame in conditions where failure in any part of the system
due to overloading, buckling, loss of hydraulic pressure or any other cause might constitute a
hazard to personnel.
The hydraulic jack, pump, hoses, pipes, couplings and other apparatus to be operated under
hydraulic pressure shall be capable of withstanding a test pressure of 1.5 times the maximum
working pressure without possible leaking.

The maximum test load or test pressure expressed as a reading on the gauge in use shall be
displayed and all operators shall be made aware of this limit.

If in the course of carrying out a test any unforeseen occurrence should take place, further
loading shall not be applied until proper engineering assessment of the condition has been
made and steps have been taken to rectify any fault. Reading of gauges should, however, be
continued where possible and if it is safe to do so.
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
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4.0 MATERIALS AND LABOUR

The Contractor shall supply all labour, materials and other equipment necessary for the
performance, recording and measurements of the test loads and settlement including the
supply and placing in position of kentledge used in the tests. The Contractor shall
subsequently dismantle and remove all the material and equipment used.

Throughout the duration and operation of the test loading the Contractor shall place
competent men to operate, watch and record the test.


5.0 PRELIMINARY PILES

In order to determine the required length of piles at each location, the Contractor shall install
and test preliminary piles in advance of the main piling operation for working piles. The
locations, sizes, lengths, test loads and instrumentation required for the preliminary piles are
as shown in the drawings.

Preliminary piles shall be installed with the same plant and in a similar manner as that to be
used in the construction of the contract working piles.

All preliminary piles shall be instrumented in accordance with that indicated in the drawings
and specification. After testing, the Contractor shall be responsible to hack away the
preliminary test pile if it is obstructing the construction of the basement or other foundation
works.


6.0 MEASURING DEVICES

Load measuring devices shall be calibrated before and after each series of tests, whenever
adjustments or replacements are made to the devices or at the intervals recommended by the
manufacturer of the equipment. All measuring equipment and gauges shall be calibrated
together. Certificates of calibration from an approved laboratory shall be supplied to the
Engineer for acceptance.

The Contractor’s proposed method of measuring the movement of pile heads and load shall
be submitted to the Engineer for approval.


7.0 SUPERVISION

All tests shall be carried out under the direction of an experienced and competent supervisor
conversant with the test equipment and test procedure. All personnel operating the test
equipment shall have been trained in its use. Load testing shall be carried out in the
presence of the Engineer or Engineer’s Representative.


8.0 LOADING TEST PILES

The rate of application and removal of the load may be altered or modified solely by the
Engineer. Unless otherwise decided by the Engineer the load steps and duration are as
indicated in item Test Procedure.


9.0 READINGS

Take readings of time, load and settlement and record immediately before and after the
application of each load increment or decrement, or as directed by the Engineer. A minimum
of another two readings shall be recorded at intermediate intervals.

Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
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10.0 INSTALLATION OF A TEST PILE

10.1 Inclusive Works

The works for the load tests shall include the construction and subsequent demolition of all
necessary pile caps built in rapid hardening cement to the contractor’s design which shall be
subjected to the Engineer’s approval.


10.2 Notice Of Construction

The Contractor shall give the Engineer at least 48 hours notice of commencement of
construction of any preliminary pile.


10.3 Method Of Construction

Each preliminary test pile shall be constructed in a manner similar to that to be used for the
construction of the working piles, and by the use of similar equipment and materials. Any
variation will only be permitted with prior agreement.

Extra reinforcement and concrete of increased strength will be permitted in the shafts or
preliminary piles provided prior notification is made.


10.4 Boring Record

For each preliminary pile which is to be tested a detailed record of the conditions experienced
during boring shall be made and submitted daily, not later than noon on the next working day.
Where the Engineer requires soil samples to be taken or in-situ tests to be made, the
Contractor shall present the results without delay.


10.5 Concrete test cubes

At least four test cubes shall be made from the concrete used in the preliminary test pile and
from the concrete used for building up a working pile. If a concrete pile is extended or capped
for the purpose of testing, a further four cubes shall be made from the corresponding batch of
concrete. The cubes shall be made and tested in accordance with BS1881.

The pile test shall not start until the strength of the cubes taken from the pile exceeds twice
the average direct stress in any pile section under the maximum required test load, and the
strength of the cubes taken from the cap exceeds twice the average stress at any point in the
cap under same load.


10.6 Preparation of Working Test Pile

If a test is required on a working pile the Contractor shall cut down or otherwise prepare the
pile for testing as required by the Engineer in accordance with the Specifications.


10.7 Cut-Off Level of Test Pile

The cut-off level for preliminary test pile shall be as specified.

Where the cut-off level of working piles is below the ground level at the time of pile installation
and where it is required to carry out a load test from that installation level, either allowance
shall be made in determination of the design verification load for friction which may be
developed between the cut-off level and the existing ground level, or the pile may be sleeved
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

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appropriately or otherwise protected to eliminate friction which develops over the extended
length.

The Contractor shall be responsible for the selection of the piling platform level and also the
platform level which the working piles are to be tested. The cost for the necessary sleeve or
bond length or pile length above the cut-off level of working piles shall be born by the
Contractor.


10.8 Pile Head For Compression Test

For a pile that is tested in compression, the pile head or cap shall be formed to give a plane
surface which is normal to the axis of the pile, sufficiently large to accommodate the loading
and settlement-measuring equipment and adequately reinforced or protected to prevent
damage from the concentrated application of load from the loading equipment.

The pilecap shall be concentric with the test pile. The joint between the cap and the pile shall
have strength equivalent to that of the pile.

Sufficient clear space shall be made under any part of the cap projecting beyond the section
of the pile so that, at maximum expected settlement, load is not transmitted to the ground
except through the pile.


10.9 Pile Connection For Tension Pile

For a pile that is tested in tension, means shall be provided for transmitting the test load
axially to the pile.

The connection between the pile and the loading equipment shall be constructed in such a
manner as to provide a strength equal to the maximum load which is to be applied to the pile
during the test with an appropriated factor of safety on the structural design.


11.0 REACTION SYSTEMS

11.1 Compression Tests

Compression tests shall be carried out using kentledge only. Unless instructed, approved or
specified by the Engineer, tension piles, ground anchors or otherwise specially constructed
anchorage shall be not be used.

Where kentledge is to be used, it shall be supported on cribwork, disposed around the pile
head so that its center of gravity is on the axis of the pile. The bearing pressure under
supporting cribs shall be such as to ensure stability of the kentledge stack. Kentledge shall
not be carried directly on the pile head, except when directed by the Engineer.
The kentledge may consist of concrete blocks, steel piles etc, but must be of uniform size so
that weight of the kentledge can be easily calculated.


11.2 Tension Tests

Tension tests shall be carried out using compression piles or rafts constructed on the ground.
The use of inclined reaction piles, anchors or rafts is not precluded, subject to agreement. In
all cases the resultant force of the reaction system shall be co-axial with the test pile.


11.3 Spacing

Where kentledge is used for loading vertical piles in compression, the distance from the edge
of the test pile to the nearest part of the crib supporting the kentledge stack in contact with the
ground shall be not less than 1.3m
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The center-to-centre spacing of vertical reaction piles, including working piles used as
reaction piles, from a test pile shall be not less than three times the diameter of the test pile or
the reaction piles or 2m whichever is the greatest.

Where a pile to be tested has an enlarged base, the same criterion shall be apply with regard
to the pile shaft, with the additional requirement that no surface of a reaction pile shall be
closer to the base of the test pile than one haft of the enlarged base diameter.

Where vertical reaction piles penetrate deeper than the test pile, the center-to-centre spacing
of the reaction piles from the test pile shall be not less than five times the diameter of the test
pile or the reaction piles whichever is the greatest unless the base capacity of the test pile is
less than 20% of the total ultimate capacity.

Where ground anchorages are used to provide a test reaction for loading in compression, no
section of fixed anchor length transferring load to the ground shall be closer to the test pile
than three times the diameter of the test pile. Where the pile to be tested has an enlarged
base the same criterion shall apply with regard to the pile shaft, with the additional
requirement that no section of the fixed anchor transferring load to the ground shall be closer
to the pile base than a distance equal to the base diameter.


11.4 Adequate Reaction

The size, length and number of reaction piles or the area of the rafts, shall be adequate to
transmit the maximum test load to the ground in a safe manner without excessive movement
or influence on the test pile.


11.5 Care Of Piles

The method employed in the installation of any reaction piles or rafts shall be such as to
prevent damage to any test pile or working pile.


11.6 Working Piles as Reaction Piles

The Contractor shall no use working piles a reaction piles.


11.7 Loading Arrangement

The loading arrangement used shall be designed to transfer safely to the test pile the
maximum load required in testing. Full details shall be submitted to the Engineer prior to any
work related to the testing process being carried out on the Site.

11.8 Pilecaps and Structural Elements

Temporary pilecaps and other structural elements forming part of the reaction system
proposed by the Contractor shall be designed and built by the Contractor, and to the approval
of the Engineer. The cost of building and demolishing such pilecaps and structural elements
shall be borne by the Contractor.


12.0 EQUIPMENT FOR APPLYING LOAD

12.1 General

The equipment used for applying load shall consist of one or more hydraulic rams or jacks.
The rams or jacks shall be arranged in conjunction with the reaction system to deliver an axial
load to the test pile. The complete system shall be capable of transferring the maximum load
required for the test.
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12.2 Jack Capacity

The total capacity of the jacks shall exceed by 20% or more the required maximum test load,
thereby avoiding heavy manual pumping effort when nearing maximum load and minimizing
the risks of any leakage of oil through the seals.

The loading equipment shall be capable of adjustment throughout the test to obtain a smooth
increase of load or to maintain each load constant at the required stages of a maintained load
test.

The length of stroke of a ram shall be sufficient to cater for deflection of the reaction system
under load plus a deflection of a pile head up to 15% of the pile shaft diameter unless
otherwise specified.


13.0 MEASUREMENT OF LOAD

13.1 Load Measurement Procedure

The load shall be measured by a load measuring device and by a calibrated pressure gauge
included in the hydraulic system. Reading of both the load measuring device and the
pressure gauge shall be recorded. In interpreting the test data, the values given by the load
measuring device shall normally be used. The pressure gauge readings are required as a
check for gross error. The pressure gauge shall have been recently calibrated.

The load measuring device may consist of a proving ring, load measuring column, pressure
cell, vibrating wire load cell or other appropriate system. The load cells or proving ring shall
be calibrated immediately prior to the test and a certificate shall be submitted to the Engineer.

A spherical seating shall be used in conjunction with any devices that are sensitive to
eccentric loadings; care must be taken to avoid any risk of buckling. Load measuring devices
and jacks shall be short in axial length in order to achieve the best possible stability. The
Contractor shall pay attention to details in order to ensure that axial loading is maintained.

Any increments of load shall not be allowed to fall below 1% of the specified load.

The Engineer’s agreement shall be obtained in writing prior to any modification of this
procedure.


13.2 Calibration of Load Measuring Devices

The load measuring device shall be calibrated before and after each series of tests, whenever
adjustments are made to the device or at intervals appropriate to the type of equipment. The
pressure gauge and hydraulic jack shall be calibrated together.

Certificates of calibration performed by an approved testing laboratory shall be supplied to the
Engineer prior to carrying out the load test.


13.3 Measurement Of Settlement

Settlement shall be measured by use of a reference beam or wire supported independently of
the test pile, reaction pile or piles supporting reaction loads. Settlements shall be measured
to the nearest 0.1mm for reference beams or 0.5mm of reference wires. A precise optical
level shall be used to check movements of the reference frame against an independent
datum. The reference beam supports shall be located at least 3m from the test pile, reaction
pile or piles supporting reaction loads. The reference beams or wires shall be protected from
the effects of temperature changes. Construction equipment and persons not involved in the
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test shall be kept well clear to avoid disturbance of the measuring system. Pile driving or
similar operations will not be permitted in the vicinity of the test unless the Engineer is
satisfied that the measuring system will not be affected.

Deflections shall be precisely measured by four dial gauges equally spaced around the pile
head to accuracy of 0.01mm to give useful information on pile bending as well as axial
movement. These dial gauges shall be firmly attached to the reference beams, so that the
plungers are parallel to the pile axis. The plunger points shall bear onto reference plates by
means of machined plates or glass slides attached to the pile head. The reference plates
shall be equidistant from the centre of the pile, diametrically opposed, and carefully aligned so
that they are perpendicular to the pile axis in order that sideways movements do not produce
any axial components.

Before stacking up of the kentledge or construction of the reaction piles / ground anchors, the
preparation of the pile head shall be carried out and the reduced level of the pile head
surveyed and recorded.


13.4 Initial Zero Load Readings

Before the first increment of test load is applied, all gauges shall be read at 30 minutes
intervals over a period of 24 hours under zero load to determine the effect of variable site
conditions on the test pile. Air temperature shall be recorded with each set of readings. The
test set-up shall be exactly as during the test proper, with the loading jack in position but clear
of the loading frame.


14.0 MEASURING MOVEMENT OF PILE HEADS

14.1 Maintained Load Test

In a maintained load test, movement of the pile head shall be measured by one of the primary
systems and one of the secondary systems described in this section.


14.2 Primary System

An optical or any other leveling method by reference to an external datum may be used.

Where a level and staff are used, the level and scale of the staff shall be chosen to enable
readings to be made within an accuracy of 0.5mm. A scale attached to the pile or pilecap
may be used instead of a leveling staff. At least two datum points shall be established on
permanent objects or other well-founded structures, or deep datum points shall be installed,
so that any one datum point can be re-established in case it is inadvertently demolished.
Each datum point shall be situated so that only one setting of the level is needed.

No datum point shall be affected by the test loading or other operations on the Site.

Where another method of leveling is proposed, this shall be agreed in writing.


14.3 Independent Reference Frame

An independent reference frame may be set up to permit measurement of the movement of
the pile. The supports for the frame shall be founded in such a manner and at such a
distance from the test pile, kentledge support cribs, reaction piles, anchorages and rafts that
movements of the ground in vicinity of the equipment do not cause movement of the
reference frame during the test which will effect the required accuracy of the test.

Observations of any movements of the reference frame shall be made and a check shall be
made of the movement of the pile head relative to an external datum during the progress of
the test. Supports for the reference frame shall be placed not less than three test pile
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diameters or 2 metres, whichever is the greater, from the center of the test pile, and not less
than 1 metres from the nearest corner of the kentledge support crib.

The measurement of pile movement shall be made by 4 dial gauges equally spaced around
the pile and equidistant from the pile axis. Dial gauges shall be rigidly mounted on the
reference frame and bear on surfaces which are normal to the pile axis and fixed to the
pilecap or head.

Alternatively the gauges may be fixed to the pile and bear on surfaces on the reference
frame. The dial gauges shall have a travel of 50mm and shall be accurate to 0.01mm.

The reference frame shall be protected from direct sunlight, wind and rain.


14.4 Secondary Systems

14.5 Reference Wire

A reference wire shall be held under constant tension between two rigid supports founded as
in the method used for the primary Reference Frame system. The wire shall be positioned
against a scale fixed to the pile and the movement of the scale relative to the wire shall be
measured.

Observations of any movements of the supports of the wire shall be made or a check shall be
made of the movement of the pile head as in the method used for primary Reference Frame
systems. Readings shall be taken to within an accuracy of 0.5mm.

The reference wire shall be protected from direct sunlight, wind and rain.


14.6 Other Methods

The Contractor may propose and implement any other suitable and adequate method of
measuring the movement of pile heads subject to the prior agreement of the Engineer.


14.7 Instrument Calibration

Prior to carrying out the load test, the Contractor shall submit to the Engineer the calibration
certificates of dial gauges performed by an approved testing laboratory.


14.8 Night Readings

The entire test area shall be adequately lighted up during the night to facilitate taking
readings.


15.0 PROTECTION OF TESTING EQUIPMENT

15.1 Protection From Weather

Throughout the test period, all equipment for measuring load and movement shall be
protected from direct exposure to sunlight, wind and rain.


15.2 Prevention Of Disturbance

Construction equipment and persons who are involved in the testing process shall be kept at
a sufficient distance from the test to avoid disturbance to the measurement apparatus.


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16.0 SUPERVISION

16.1 Notice Of Test

The Contractor shall give the Engineer at least 24 hours notice of the commencement of the
test.


16.2 Records

During the progress of a test, the testing equipment and all records of the test as required
under the section headed 'Presentation Of Results' in this specification shall be available for
inspection by the Engineer.


17.0 TEST PROCEDURE

17.1 Failure Load Tests (Preliminary Test Pile)

Failure Load Tests shall be performed on preliminary piles designated by the Engineer at the
commencement of the contract to verify the design parameters used and to determine the
lengths of subsequent working piles. The preliminary piles shall be the only ones made in the
first instance, and the load tests carried out prior to the installation of any other piles. Piling
works shall not commence until after the failure load test results have been analysed, and
upon instruction by the Engineer.

The provisional number of Failure Load Test shall be as specified in the Bills of Quantities.
However, the Engineer reserves the right to alter the number of tests subject to the nature of
subsoil conditions encountered and the pile system adopted vis-à-vis the method of
installation, material and plant usage.

The test procedure shall be as follows, with the percentage for loading and unloading
operations given in terms of the working load taken as 100%:


LOADING CYCLES FOR PRELIMINARY PILES
Load Percentage Of Working Load Time Of Holding Load (minutes)
0 10
10 10
20 10
30 10
40 10
50 10
60 10
70 10
80 10
90 10
100 60 min or settlement rate less than 0.25 mm/hr (whichever is longer)
75 10
50 10
25 10
0 30
25 10
50 10
75 10
100 10
110 10
120 10
130 10
140 10
150 10
160 10
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

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170 10
180 10
190 10
200 60 min or longer as instructed by the Engineer
150 10
100 10
50 10
0 30
50 10
100 10
150 10
200 10
210 10
220 10
230 10
240 10
250 10
260 10
270 10
280 10
300 60 min or longer as instructed by the Engineer
200 10
100 10
0 30

The test schedule for compression test is for guidance only. It is subject to variation by the
Engineer to meet site conditions.

The procedure for tension pile tests shall be exactly as described in this section for
compression pile test; for tension test, the words “settlement” and “rebound” should be read
“displacement” in the column “action to be taken after Load Stage.”

For failure load tension pile test, the Contractor shall provide adequate reinforcement in the
test pile to carry the ultimate tension load. It is held that the cost of each reinforcement is
included in unit rate for test pile.

All loading and unloading operations shall take place during the day. Pressure gauge
readings shall be recorded at each load increment or at each decrease in load. During
waiting periods at various loading stages, all readings shall be recorded after the load has
been applied and before the commencement of next loading stage. Take readings at 15
minute intervals at 100%, 200% and 300% of working load.

If large discrepancies occur between different measurement systems, the test shall
be halted and the cause for the discrepancy corrected. The test shall be restarted
from the beginning in this instance.


19.1 Working Load Test on Working Piles

A number of working load tests on 2.0 times the working capacity of the pile shall be carried
out on working piles to be designated by the Engineer, and in accordance with BS 8004: 1986
Clause 7.5.5. In case of discrepancies the provision of this specification shall take
precedence. The Contractor shall submit a detailed proposal of load tests to the Engineer,
and shall obtain his approval in writing before carrying them out. On completion of the test,
the Contractor shall submit to the Engineer the test results, including graphs showing load
and settlement versus time and settlement versus load.

The provisional number of working load tests to be carried out shall be specified. The
Engineer may reduce the number of tests if a consistent high quality of workmanship and pile
material is well established and if the nature of soil conditions encountered does not vary
substantially, Conversely, the Engineer reserves the right to increase the number of tests
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either to verify the quality of workmanship and pile material or in response to variable subsoil
conditions.

Unless otherwise specified by the Engineer, the test procedure shall be as follows, with the
percentage for loading and unloading operations given in terms of the working load, taken as
100%:


TABLE 1: LOADING CYCLES FOR WORKING PILES
Load. Percentage Of Working Load Time Of Holding Load (minutes)

0 10
10 10
20 10
30 10
40 10
50 10
60 10
70 10
80 10
90 10
100 60 min or settlement rate less than 0.25min/hr (whichever is longer)
75 10
50 10
25 10
0 30
25 10
50 10
75 10
100 10
110 10
120 10
130 10
140 10
150 10
160 10
170 10
180 10
190 10
200 60 min or longer as instructed by the Engineer
150 10
150 10
50 10
0 30


The test schedule for compression test is for guidance only. It is subject to variation by the
Engineer to meet site conditions.

The procedure for working load tension pile tests shall be exactly as described in this section
for compression pile tests; for tension test, the words "settlement" and "rebound" should be
read "displacement" in the column "action to be taken after Load Stage".

All loading and unloading operations shall take place during the day. Minimum three (3) sets
of readings shall be taken in each loading stage: one set each at the beginning, middle and
end of each loading or unloading stage. When a test load is maintained for more than 30
minutes, readings shall be taken at maximum half-hourly intervals thereafter unless otherwise
specified by the Engineer.

If large discrepancies occur between different measurement systems, the test shall be halted
and the cause for the discrepancy corrected. The test shall be restarted from the beginning in
this instance.
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
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18.0 ABANDONMENT OF PILE TEST

Test shall have to be discontinued if any of the following occurs:

- faulty jack or gauge,
- instability of kentledge,
- improper setting of datum, or
- unstable Bench Marks or Scales,
- measuring instruments used are found to have been tampered with by anyone,
- pre-jacking or pre-loading before commencement of the test.

Should any test be abandoned due to any of the above causes, the Contractor shall carry out
further tests to the Engineer instructions after rectification of the errors.


19.0 PRESENTATION OF RESULTS

19.1 Results To Be Submitted

A written summary to the Engineer within 24 hours (or unless otherwise directed) of the test,
which shall give:

(i) For each stage of loading, the period for which the load was held, the load and the
maximum settlement or uplift recorded.

(ii) Load vs. Settlement curve.

The completed schedule of recorded data as described hereunder in this section shall be
submitted to the Engineer within seven days of completion of the test.


19.2 Schedule Of Recorded Data

The Contractor shall provide information about the tested pile in accordance with the following
schedule where applicable.


19.3 General

* Site location
* Contract identification
* Proposed structure
* Main Contractor
* Piling Contractor
* Engineer
* Client
* Data of test


19.4 Pile Details

All piles
* Identification (no. and location)
* Position relative to adjacent piles
* Brief description of location (e.g. in cofferdam, in cutting, over water)
* Ground level at pile location
* Head level at which test load is applied
* Type of pile (e.g. precast reinforced concrete, steel H, bored in place, driven in place,
composite type)
* Vertical or raking, compression or tension
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* Shape and size of cross-section of pile, position of change in cross-section
* Shoe or base details
* Head details
* Length in ground
* Level of toe


19.5 Installation Details

To follow the Bored Piling Specification.


19.6 Test Procedure

* Weight of kentledge.
* Tension pile, ground anchor or compression pile details
* Plan of test arrangement showing position and distances of kentledge support, rafts,
tension or compression piles and reference frame to test pile
* Jack capacity
* Calibration certificates of pressure gauges and dial gauges
* Method of load measurement
* Method(s) of penetration or uplift measurement
* Proof test by maintained loading
* Relevant dates and times


19.7 Test Results

* In tabular form
* In graphical form: log P plotted against log S (only for Failure Load Tests), load plotted
against settlement (or uplift load and settlement or uplift) plotted against time, load
distribution with depth (if strain gauges are available), settlement of pile shaft at different
depth (if extensometers are available), load settlement (load transfer) for shaft at different
depths (if strain gauges and extensometers are available).
* Ground heave


19.8 Site Investigation

* Site Investigation report reference number and coordinate or grid reference
* Borehole reference


20.0 COMPLETION OF A TEST

20.1 Measuring Equipment

On completion of a test, all equipment and measuring devices shall be dismantled, checked
and either stored so that they are available for use in future tests or removed from the Site.


20.2 Kentledge

Kentledge and its supporting structure shall be removed from the test pile and stored so that
they are available for use in future tests or removed from the Site.


20.3 Ground Anchors And Temporary Piles

On completion of a Failure Load Test, temporary pile and ground anchors shall be cut off
below ground level, removed from the Site and the ground made good with approved
material.
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

55

The pilecap, if formed in concrete, shall be broken up and removed from the Site. If the
pilecap is made of steel, it shall be cut off and either stored so that it is available for use in
further tests or removed from the Site.


20.4 Preliminary Test Pile

Preliminary test piles which are not to be incorporated into the permanent works shall be
broken down to 2m below ground level or as required, and the ground backfilled to the
original level with approved material. For preliminary test piles which are to be incorporated
into the permanent works, the pile head shall be made good or extended to the cut off level in
the manner described in the section headed “Installation of a Test Pile” in this specification.


21.0 DETERMINATION OF ULTIMATE LOAD FROM THE FAILURE LOAD TEST RESULT

As general guide for test completion, failure load test shall terminate when the test pile settles
by an amount equal to 10% of the effective pile diameter, but for a pile effective diameter not
exceeding 250mm the corresponding pile head settlement shall be 25mm maximum. The
foregoing guideline is given subject always to the condition that all failure load test shall be
taken beyond the ultimate load of the pile. The load test may be terminated earlier at lower
total settlement provided the Contractor can adequately demonstrate to the satisfaction of the
Engineer, by load-settlement curve method or otherwise, that the ultimate load for the test pile
has been exceeded at that settlement.

The ultimate bearing capacity of the test pile, if well defined in the load versus settlement
curve plotted from the load test data, shall be taken as the ultimate load which is the load with
a corresponding pile head settlement of not more than the lesser of 10% of the effective pile
diameter or 25mm. In this case, the working load of the pile shall be taken as ultimate load
divided by a factor of safety.

If the ultimate bearing capacity of the test pile is not well defined in the load versus settlement
curve plotted from the load test data, the yielding load shall be taken as the lesser of either:

a. the load where the load (P) versus settlement (S) curve becomes steep and straight,
or
b. the load where the log P versus log S curve shows a change in slope.

Subject to the agreement of the Engineer and provided always that the corresponding pile
head settlement does not exceed an amount equal to the lesser of 10% of the effective pile
diameter or 25mm. In this case, the working load of the pile shall be taken as yielding load
divided a factor of safety.

The effective pile diameter shall be considered as the diameter of the circle inscribed in the
section of the pile.


22.0 HIGH STRAIN DYNAMIC TESTING OF PILES

22.1 General

High Strain Dynamic testing of piles shall be carried out by an independent testing
organisation approved by the Engineer.

If the results of the tests show that the pile or piles are defective, the pile or piles shall be
treated as faulty and shall be rejected unless the Contractor can demonstrate to the approval
of the Engineer effective remedial measures that will be carried out.

The Engineer’s interpretations and conclusions arrived at on the test results shall be final.

Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

56
All preliminary pile shall be subject to high strain dynamic test before and after the static load
test.


22.2 High Strain Dynamic Test

High Strain Dynamic Test shall be conducted on working piles to be selected by the Engineer
as the work progresses.

Dynamic Pile Testing is carried out for any of the following: -

- Determination of pile bearing capacity
- Determination of pile integrity
- Determination of pile stress during driving
- Determination of hammer efficiency

All tasks require measurement of both axial pile forces and accelerations under at least one
hammer blow. A permanent pile set of more than 1.2mm per blow is recommended for
activation of soil resistance. Smaller sets may under-predict static capacity. For integrity,
permanent set is not required, but the blow should cause motion of the pile toe.

i) Apparatus For Applying Impact Force

The apparatus for applying the impact force shall be either a conventional pile driving
hammer or a similar device acceptable for applying the impact force provided it is
capable of generating a net measurable pile penetration, or an estimated mobilised
static resistance in the bearing strata which, for a minimum period of 3 milliseconds,
exceeds the working load assigned to the pile. The driving apparatus shall be
positioned so that the impact is applied axially to the head of the pile and concentric
with the pile.

ii) Apparatus For Obtaining Dynamic Measurements

The apparatus shall include transducers, which are capable of independently
measuring strain and acceleration versus time at a specific location along the pile
axis from the moment of impact until the pile comes to a rest. The transducers shall
be placed at the same location diametrically opposed, and on equal distances from
the longitudinal axis of the pile so that the measurements are not affected by bending
of the pile. At the upper end of the pile they shall be attached at least one and one-
half to three pile diameters from the pile head. Care shall be taken to ensure that the
apparatus is securely attached to the pile so that slippage is prevented. The
apparatus shall be calibrated to an accuracy of 2 percent throughout the applicable
measurement range. If damaged is suspected during use, the transducers shall be
recalibrated or replaced.

Force measurements shall be made by strain transducers. A minimum of two of
these devices shall be securely attached to the pile on opposite sides of the pile so
that they do not slip. Bolt-on, glue-on or weld-on transducers are acceptable. The
strain transducers shall have a linear output over entire range of possible pile strains.

Velocity data shall be obtained with accelerometers. A minimum of two
accelerometers with a resonant frequency above 10,000 Hertz shall be attached to
the pile securely on diametrically opposite sides of the pile so that they do not slip
and at equal distances from the pile axis. Bolt-on, glue-on and weld-on transducers
are acceptable. The accelerometers shall be linear to at least 1,000g and 10,000
Hertz for satisfactory result on concrete piles. Either a.c. or d.c. accelerometers shall
be used. If a.c. devices are used, the time constant shall be a least one second.

iii) Apparatus For Recording, Reducing And Displaying Data

The signals from the transducers during the impact event shall be transmitted to an
apparatus for recording, reducing and displaying data to allow determination of the
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

57
force and velocity versus time. The acceleration and displacement of the pile head,
and the energy transferred to the pile shall be determined. The apparatus shall
include an oscilloscope or screen for displaying the force and velocity, a tape
recorder for obtaining a record for future analysis, and a means to reduce the data.
The apparatus for recording, reducing and displaying data shall have the capability of
making an internal calibration check of force, velocity and time scales. No error shall
exceed 2 percent of the maximum signal expected.

Signals from the transducers by means of an apparatus on which the force and
velocity versus time can be observed for each hammer blow such as an oscilloscope
or oscillograph. Both the force and velocity data shall be reproduced for each blow
and the apparatus shall be capable of holding and displaying the signal from each
selected blow for a minimum period of 30 seconds.

iv) Dynamic Measurements

Dynamic properties shall be determined from a minimum of ten impact records during
initial driving. Soil resistance computations shall be determined from one or two
representative blows at the beginning of restriking. The force and velocity versus
time signals shall be reduced by computer or manually to calculate the developed
force, velocity, acceleration, displacement, and energy over the impact event. The
number of impact for a specific penetration ram travel length, and the number of
blows per minute delivered by the hammer shall be recorded. The testing shall be
performed by an experienced engineer in the field of dynamic testing.

v) Submission Of Test Records

The Contractor shall submit all records of results and any other information to the
Engineer within three (3) days from the completion of the test.

The results shall consist of the stresses in piles, pile integrity, hammer performance,
pile bearing capacity, and whatever information deemed necessary for the report.

For preliminary test and complicated cases, CAPWAP laboratory analysis shall be
carried out.

The Engineer’s interpretation and conclusion arrived at on the test result shall be
final.

vi) CAPWAP Computer Analysis Program

The outputs shall consist of matches of forces and velocities, resistance distribution,
static simulation and complete tables of numeric values.

The specialist Contractor shall complete and provide the following: -

- Static capacity of pile including the toe resistance and shaft friction
- Hammer Efficiency
- Integrity of Pile
- Case Damping Factor Jc
- Predicted Load Vs Settlement Plots

CAPWAP computer analysis report shall be submitted to the Engineer within seven
(7) days from the issuance of instruction.

The report shall contain complete analysis, result and their interpretation.






Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

58
23.0 SHOCK METHOD

23.1 Preparation of the Pile Head

The pile head shall be clearly exposed, free from debris, etc. and not more than 1.0 metre
above or below ground level, otherwise the surrounding soil shall be built up or excavated to
meet this condition. The pile head shall be smooth over its complete cross-section, free from
irregularities and perpendicular to the vertical axis of the pile.

The pile head shall consist of sound concrete. This shall be achieved during the concreting of
the pile by flushing out all weak mortar, etc. from the top of the pile head and carefully
screeding off to provide a smooth level surface in sound concrete. Alternatively, if the pile
head is prepared after concreting, all weak mortar, broken concrete, etc. shall be removed
form the pile head to expose sound concrete over its complete cross-section. After cleaning it
off to ensure a sound bond, a very thin screed (maximum 1cm) of strong sand/cement mortar,
rapid hardening compound, shall be spread to provide a smooth working surface for the
shock test equipment. The mortar shall be allowed to harden before testing. The soundness
shall be tested by means of light blows from a small hammer.

Any reinforcement or other inclusions protruding from the pile head shall not prevent the
testing team from giving the pile the required impact force over the centre of the pile and the
placing of a 5cm diameter (approx.) electronic pick-up at about 10cm from the periphery of
the pile. Access shall be provided for the service van within 30 metres of the pile.


23.2 Shock Test Equipment

The shock which is to be imparted onto the pile head shall be carried out using a suitable
hammer or any approved method which is capable of transmitting vibration to the base of the
pile shaft. The electronic pick-ups located on the pile head shall be approved velocity
transducers or accelerometers connected through an approved frequency analysed to any X-
Y plotter. The mechanical admittance shall be plotted on a vertical scale and the frequency on
the horizontal scale. Both the horizontal and vertical scales shall be varied as required. The
equipment shall have an independent power supply.


23.3 Shock Test

The Contractor shall provide the testing team with a site plan showing the pile layout and a list
of the piles to be tested.

Before testing, the heads of the piles shall be inspected by the testing team for regularity and
soundness and any unsatisfactory pile heads reported to the Engineer. They shall be made
good to the satisfaction of the Engineer and smoothed off using a suitable epoxy mortar if
necessary. Preliminary tests shall be carried out to establish the appropriate scales and to
check the electronic circuit.


24.0 SONIC LOGGING METHOD

For the purpose of carrying out sonic logging, the Contractor shall be required to install the
necessary tubing for the tests at all pier location or as directed by the Engineer.

The tubes shall be of internal diameter not less than 50mm with no internal projections or
couplings. They can be of mild steel pipes or PVC pipes. Four (4) nos. of tubes are required
for each pile greater than 700mm diameter while three (3) nos. are required for each smaller
diameter pile.

The tubes shall be fixed to the longitudinal bars with equal spacing on the inside perimeter of
the links. The tubes shall be watertight with the bottom of the tube sealed and suitably
weighted to prevent floating. The tubes shall be secured to the internal face of the
reinforcement cage at equal distance from each other on the circumference.
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

59

The tubes shall extend the full depth of the pile and project 300mm above the top of the
concrete and not lower than 300mm below the surface of the ground. All joints shall be made
watertight. The tubes shall be filled with water to provide the necessary acoustic coupling, and
then plugged or capped before concreting. The type of tube and condition of sealing shall be
checked and approved by the Engineer before installation.

The rate of logging for increments of depth shall be approved by the Engineer.

After conducting the tests, all metal tubes shall be grouted and water in the tubes displaced.
The grout shall be dense cement grout with an approved expanding agent.

Prior to testing, the necessary equipment shall be thoroughly checked to ensure that all parts
are functioning satisfactorily. During sonic logging testing, where any irregularities are
detected, the tests shall be repeated at a smaller scale to allow a "close-up view” of the
irregularities.


25.0 PRESENTATION OF TEST RESULTS

The time required to carry out the test for each pile must be recorded along with records of
starting time and finishing time.

The results of the tests shall be presented in report form by the testing firm and must be
signed by a professional engineer. The report shall include comprehensive engineering
analysis of the test results for each pile taking into consideration the soil condition and any
other relevant factors. Interim reports of each pile or group of piles tested in one day shall be
submitted to the Engineer within 3 days of the completion of the test or tests. A final
comprehensive report shall be submitted to the Engineer within 10 days of the completion of
the last test or tests.


26.0 PROOF CORING OF PILE SHAFTS

The Contractor shall check the quality of the concrete in the shafts of working piles as
directed by the Engineer. This shall be achieved by a vertical diamond core hole drilled
through the centre region of the pile from pile head to required depth. The location of the drill
hole and depth shall be approved by the Engineer. Full core recovery shall be attempted. The
core so produced shall not be less than 50mm in diameter. The minimum number of piles for
proof coring test shall not be less than 1% of the total number of working piles.

For each pile to be cored, the coring work shall be completed before the concrete in the pile
has reached an age of 28 days to allow the cores to be tested for unconfined compression
tests at 28 days. The Engineer shall mark the sections of the core to be tested and the
Contractor shall arrange for testing in an approved laboratory. A minimum of six (6)
unconfined compression tests shall be conducted on cores obtained from a pile. Additional
number of the unconfined compression tests may be requested by the Engineer if in the
opinion of the Engineer the quality of the concrete of the pile is suspicious.

The cored hole in the pile shall be grouted after testing. The grout shall be an approved dense
cement grout with a minimum 28 days strength of 30N/mm2. If the pile is found to be faulty in
the opinion of the Engineer because of defects such as cracks, overbreaks, necking, cavity,
inclusion of foreign deleterious materials, poor quality concrete, etc., the pile shall be rejected
and the Contractor shall undertake all necessary remedial measures to the approval of the
Engineer.

In conjunction to core testing, the Engineer may request sonic logging test to be conducted in
the cored holes or pre-installed tubings to determine the in-situ density of the pile and their
integrity continuously along the pile length in correlation with core samples.



Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

60
27.0 INSTRUMENTATION FOR TEST PILES

27.1 Strain Gauges

Vibrating wire type strain gauges shall be installed in preliminary pile. The following vibrating
wire strain gauges and equipment or equivalent to the approval of the Engineer shall be used:

i) Vibrating wire type weldable strain gauge. Steel wire of length of about 60mm (e.g.
62mm), and frequency range 0.8 to 2.4 kHz and associated connections, cables and
read out device.
ii) 3M Scotchcast Insulating Resin 4.
iii) Miscellaneous small tools and materials for making concrete.

All strain gauges shall be mounted on major longitudinal steel bars of the steel cage of the
preliminary pile. The strain gauges shall be installed in sets of four and equally spaced on the
steel cage at levels directed by the Engineer. A total of 6 sets of strain gauges shall be
installed.

The steel bars shall be polished using a hand held electrical grinder to obtain a flat surface for
the strain gauges to be placed on. Polishing shall be completed by hand using silicon carbide
paper. The surfaces of the polished bars shall be cleaned using acetone.

The weldable strain gauges shall then be bonded to the steel bars using a microbond welder.
Next, the strain gauge sensors shall be placed on the strain gauges and tied firmly to the steel
bars with wires. Short lengths of PVC protective pipe shall be placed over the strain gauge
locations, and filled with insulating resin.

The electrical lead wires from the sensors shall be brought to the top of the pile through PVC
pipes tied to the steel cage.

The gauges shall be checked before and after microwelding, after installation, after placement
of the steel cage in the borehole, and after concreting.


27.2 Rod Extensometers

A system of sleeved rods to the approval of the Engineer shall be installed in each preliminary
pile to determine the movement under testing loads. A minimum of three (3) levels within the
pile shaft shall be measured as shown in the drawings. The rod extensometers shall have the
capability of measuring movements both mechanically and electronically.


27.3 Instrumentation Installation

The Contractor shall follow the manufacturer recommended procedures for instruments
installations and shall provide a method statement for approval prior to installation. The work
shall be carried out by persons experienced in this type of work. A data Iogging system shall
be provided for all automatic recording instruments.


27.4 Instruments Identification and Recording

The leads of various instruments shall be probably identified to facilitate easy hook-up and
recording. All instrument readings shall be recorded as directed by the Engineer in approved
forms. Any sort of calibration or conversion charts shall be available on site at all times.


27.5 Monitoring

The nominated testing agency shall submit a method statement on pile instrumentation for the
Engineer's agreement before the conduct of the tests. The method statement shall give full
details of the proposed methods, equipments, specifications and precautions to be taken for
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

61
the proper installation and monitoring of pile instrumentation, and the criterion and procedure
for interpretation of results obtained, including any other relevant information required by the
Engineer. Prior to the tests, the instruments and necessary monitoring equipment shall be
checked to ensure all parts are functioning satisfactorily.

The results of the pile instrumentation and monitoring programme shall be presented in a
report prepared by the testing agency and signed by a qualified engineer. The report shall
include a comprehensive engineering analysis of the test data, taking into consideration the
soil condition and any other relevant factors. An interim report shall be submitted to the
Engineer within 3 working days after the completion of each Failure Load Test, and a final
comprehensive report shall follow 7 days later. The testing agency shall be required to
correlate the results of pile instrumentation with that of the Failure Load Test and against the
soil information available in the soil report from exploratory boreholes located in the vicinity of
preliminary test piles.

The Contractor shall make every necessary allowance for the proper execution of the
instrumentation programme. Full cooperation shall be given to the nominated agency carrying
out the tests. The Contractor shall not be allowed to claim for extra time to the contract on all
matter arising from the execution of pile instrumentation, and on any consequences arising
out of such instrumentation.

Both soft and hard copy of the report shall be submitted to the Engineer in the format
approved by the Engineer.

























Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

62


APPENDIX C
Sample Checklist for Construction of Bored Pile














Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

63
CHECKLIST FOR BORED CAST-IN-PLACE PILE

CHECKLIST ITEMS
Checked By
Engineer
Remarks

Project Name : _____________________________
Piling Contractor : _____________________________

1.0 CONSTRUCTION METHOD AND TECHNIQUES
• Pile Diameter _______________________________
• Concrete Grade _______________________________
• Pile Raked Gradient ______ Vertical : ______ Horizontal


• Grab Construction (Using Crawler Crane, Casing Oscillator,
etc)
• Rotary Drilling (Contiguous Flight Auger, Twin Head Rotary
Drive)
• Rock Coring (Chisel, Core Barrel, Cross Head Cutter,
Reamer, etc.)
q

q

q

• Direct Circulation Drill
• Indirect Circulation Drill
q
q

Concreting Method
• Poured (With Tremie for Wet Hole Construction)
• Injected

q
q

Reinforcement
• Reinforcement Cage : Main _______ Link _____________
(eg. 32T20) (eg. T12 @ 150 Spiral)
[Note: T = 460 N/mm2 , Y = 410 N/mm2 , R = 250 N/mm2 ]
• Lapping Length : ____________________________
• Concrete Cover/ Spacer : ______________________

2.0 PILING EQUIPMENT AND ACCESSORIES
Excavator:
• Crawler Crane (Grab method)
• Rotary Drive (Continuous Flight Auger, Twin Rotary Head)

• Temporary Casing
• Drilling Fluid (Bentonite or other Slurry Stabilisation)
• Concrete Tremie Pipe (for concreting under water or wet
hole)
• Hover with short length of chute (direct discharge method for
dry hole)
q

q

3.0 PILE POSITION SETTING UP
• Three reference points to be setup with respect to the
proposed pile point.

4.0 BORED PILE CONSTRUCTION
Predrilling
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

64
• To determine the bored pile length
• To check verticality of borehole
• To check any deviation in the distance of pile point to the
reference points after soil boring.
Stability Of Borehole
• Temporary steel casing with appropriate size and length
(minimum 1m or below the unstable strata) should be applied
to prevent loose materials falling into the bottom of borehole.
• Borehole to be filled with drilling fluid to stabilise the borehole
[See note ##] unless stiff clayey soils are encountered.

Verification Of Bedrock (If Required)
• Inspection of the excavated rock fragments
• The depth achieved (rock encountered / total length) to be
compared with the borehole data and checked by a
measurement tape.
• The bottom soundness is checked with a weight on a tape
tamped on the founding strata.
• In-situ rock strength test (e.g. Point Load Test) to be
conducted [See note ##]

Airlifting (Base Cleaning)
• Use cleaning bucket to clean the base before carrying out air
lifting.
• To ensure the cleanliness of the loose and caving-in soil at
base.
• Make sure the hose is at the base of the pile (not suspended
half-way).

Reinforcement Cage
• The length of the cages should match with the excavated
depth.
• Insert fabricated reinforcement cage into the cased borehole

Check Lap length (if any)
q

5.0 CONCRETING
• Concrete overbreak after each batch of concreting
• Pour in concrete (by tremie concrete method or direct
discharge method), simultaneously displacing slurry.
• Check the density of fluid as in the specification.
• The bottom end of the tremie pipe should be always about
one to two metres submerged below the level of the
concrete. (Not to pull up too abrupt)
• Concreting could only be stopped at about 1m above the cut-
off level
• Record any interruption on concreting (record the duration)
• Test Cube :
o at least 6 Nos.
o achieve design strength (within 28 days)
• Concrete Slump Test
• Record :
o Number of trucks
o Discharge amount per trucks

Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

65
6.0 PROOF DRILLING
Core drilling to be carried out through piles to check the qualities
of
• Concrete
• Contact between the rock and concrete
• Quality of the rock beneath the toe

7.0 CHECK BORED PILE SHAFT INTEGRITY
• Use High Strain Dynamic Load Test (HSDLT)
• Pile Integrity Test (PIT).
• Sonic Logging
q
q
q

8.0 POST-INSTALLATION
Penetration length
• Piling Platform level : ___________
• Borehole Drilling Record : ________
• Predicted Length at site : ________ ( from HSDLT or PIT )

Compared penetration lengths with Borehole or Proof Drilling
from Subsurface Investigation.

Check As-built position of the bored pile group
(Typically eccentricity < 75mm)

9.0 COMPUTATION
Estimate the amount of concrete and materials for each piles.

Signature by Engineer
Note : [##] represents the items that will be followed if only necessary.



















Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)

66

APPENDIX D
Design of Piles with Lateral Loadings






Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)


DESIGN OF PILES WITH LATERAL LOADINGS

Pile foundations for structures such as bridge abutments and piers for bridges are subjected to lateral
loadings that need to be assessed carefully. The design of piles subjected to lateral loadings are often
governed by lateral deflections. However, ultimate resistance may be important for:
a) Short piers
b) Long slender piles
c) Non-linear analysis of deflections

Design of pile foundations with lateral loadings requires the assessment of failure modes and head
conditions as follow:

Failure modes:
a) Short pile mode: Failure of the supporting soil
b) Long pile mode: Structural failure or yielding of the pile itself

Both modes need to be analysed, and the more critical mode established.

Head conditions:
a) Free or unrestrained head – no head restraint
b) Fixed head or restrained head – no rotation of head

In this short note, Broms’ theory on the estimation of ultimate lateral load and Randolph’s elastic
continuum approach for the estimation lateral deflections which are two of the most widely used
method will be presented.

Broms’ theory (Ultimate lateral load)

Useful and simple to use design charts for eight different categories are available:
a) Cohesive soils
i. Short and long pile failure – unrestrained head
ii. Short and long pile failure – restrained head

b) Cohesionless soils
i. Short and long pile failure – unrestrained head
ii. Short and long pile failure – restrained head





67
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)





































Figure 1: Short Pile in Cohesive Soil









68
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)





























Figure 2: Short Pile in Cohesionless Soil














69
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)



























Figure 3: Long Pile in Cohesive Soil
















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Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)





















Figure 4: Long Pile in Cohesionless Soil

The above charts are simple and easy to use. The required information for the determination
of ultimate lateral resistance is:
a) Undrained shear strength, c
u
(for cohesive soil)
b) Coefficient of passive earth pressure, K
p
and density of soil, γ (for cohesionless soil)
c) Yielding moment for pile, M
u

d) Embedded pile length, L
e) Pile diameter / width, B
f) Height from the ground surface to the point of application of the load (free head pile),
e

For design, both short pile and long pile mode of failures need to be considered and the
most critical value adopted.

Example:
Determine the required embedment depth of a φ800mm bored pile sustaining a horizontal
load of 960 kN (restrained head). Undrained shear strength of soil =75 kPa.

For short pile failure mechanism, H
u
/ c
u
B
2
=20, from Figure 1: L/B =4

Therefore, required L =4 x 0.8 =3.2m x 2.5 (FOS) =8.0m

In addition, adequate reinforcement should also be provided for the bored pile to sustain
bending moment given by:

For long pile failure mechanism, from Figure 3: M
u
/ c
u
B
3
=30,

Therefore, M
u
=30 x 75 x 0.8
3
=1152 kNm
71
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)


Randolph’s elastic continuum approach (Lateral deflections)

For the application of this approach, Randolph has introduced the following parameters:
a) Shear modulus, G
*
=G (1 +3ν/4)
b) Variation of shear modulus, ρ
c
=G*
lc/4
/ G*
lc/2

c) For an equivalent pile of radius r
o
, Young’s modulus, E
p
=(EI)
p
/ (πr
o
4
/4)

Definition of the above parameters are as shown in Figure 5.

















Figure 5: Definition of ρ
c
and G
c




The critical pile length is defined by Randolph as:

l
c
= 2r
o
(E
p
/G
c
)
2/7
(1)

It may be seen from Figure 5 that the definition of G
c
requires the knowledge of the critical length
which is in turn defined in terms of G
c
. Thus some iteration is required except for the extreme cases of
homogeneous soil (ρ
c
=1) and soil where G is proportional to depth (ρ
c
=0.5), where the critical
length reduces to:

l
c
= 2r
o
(E
p
/m*r
o
)
2/9
(2)
where m* is the rate of increase of G
*
with depth.

72
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)


With the concept of a characteristic shear modulus, G
c
and a critical pile length, l
c
introduced, the
lateral deflection, u and rotation, θ are given by:

u = [ (E
p
/G
c
)
1/7
/ ρ
c
G
c
] [0.27 H (l
c
/2)
-1
+ 0.30 M (l
c
/2)
-2
] (3)

θ = [ (E
p
/G
c
)
1/7
/ ρ
c
G
c
] [0.30 H (l
c
/2)
-2
+ 0.80 (ρ
c
)
1/2
M (l
c
/4)
-3
] (4)

where H =lateral load and M =moment

According to Randolph, the maximum moment for a pile under a lateral load of H, occurs at a depth
between l
c
/4 (for homogeneous soil) and l
c
/3 (for soil with stiffness proportional to depth). The value of
the maximum moment may then be estimated as:

M
max
= (0.1/ρ
c
) H l
c
(5)

For piles within a group, the pilecap may prevent rotation of the head of the pile. For such “fixed-
headed” piles, Equations (3) and (4) may be used to find the fixing moment, M
f
. Setting θ =0, the
fixing moment is given by:

M
f
= - [0.375 / (ρ
c
)
1/2
] H l
c
/2 (6)

The resulting deflection of the pile head may then be calculated from Equation (3):

u
f
= [ (E
p
/G
c
)
1/7
/ ρ
c
G
c
] [0.27 - 0.11 / (ρ
c
)
1/2
] H (l
c
/2)
-1
(7)

It is important to take note that the above equations are for piles longer than their critical length. For
piles shorter than their critical length, the head deformation will be larger especially when the pile
length falls below about 0.8 l
c
. Solutions for short piles will not be discussed here and interested
readers may refer to works by Carter & Kulhawy (1988) and Poulos & Davis (1980).

Example (after Fleming et. al, 1994):
Consider the response of a steel pipe pile, 1.5m in diameter, with 50mm wall thickness, embedded in
soft, normally-consolidated clay with a shear strength which increases at a rate of 2.5 kN/m
2
per
metre of depth. The equivalent modulus of the pile is calculated as:

E
p
=E
steel
[1 – (r
i
/r
o
)
4
] =50600 MN/m
2

where
r
i
=inner radius of the pile
E
steel
=210 GN/m
2


73
Geotechnical Course for Pile Foundation Design & Construction, Ipoh (29 – 30 September 2003)
Design & Construction of Bored Pile Foundation (by Y.C. Tan & C.M. Chow)


Taking a shear modulus for the soil of G =100c
u
=0.25z MN/m
2
and Poisson’s ratio, ν =0.3, the
critical pile length may be calculated as:

l
c
=2r
o
(E
p
/m*r
o
)
2/9
=2(0.75)[50600/(0.306 x 0.75)]
2/9
=23.1 m

where m* =0.25 (1 +0.75x0.3) =0.306 MN/m
3
. The value of G
c
is then given as:

G
c
=G*
lc
/ 2 =23.1 x 0.306 / 2 =3.53 MN/m
2

ρ
c
=0.5

Therefore, under a lateral load of 1 MN, with no rotation allowed at ground level, the maximum
bending moment and ground level deflection may be calculated from Equations (6) and (7):

M
f
=- [0.375 / (0.5)
1/2
] (1) (23.1)/2 =-6.1 MNm
u
f
=[ (50600/3.53)
1/7
/ (0.5 x 3.53) ] [0.27 - 0.11 / (0.5)
1/2
] (1) (23.1/2)
-1
=22.0 mm

74

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