CONTENTS
Page
1.
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GENERAL
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3
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1.1
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Scope
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3
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1.2
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Related Sections
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3
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1.3
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Standards and Regulations
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3
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1.4
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Trade Preambles
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4
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1.5
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Definitions
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6
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2.
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PERFORMANCE REQUIREMENTS
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8
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2.1
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Contractor’s Proposal
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8
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2.2
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Pile Testing Requirements
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8
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2.3
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Permissible Damage Criteria for Existing Critical Structures or Services
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8
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3.
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EQUIPMENT
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9
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3.1
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Calibration
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9
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3.2
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Static Load Test
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9
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3.3
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Osterberg Cell Load Test Equipment
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9
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3.4
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Dynamic Load Test Equipment
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10
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3.5
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Sonic Logging Equipment
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10
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3.6
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Vibration Test Equipment
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10
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3.7
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Modified Shock Test Equipment
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10
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3.8
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Simple Shock Test Equipment
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11
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1. GENERAL
Read with the General Requirements section,
and
all other contract documents.
1.1 Scope
This section covers the requirements for the load and integrity testing of bored and driven piles.
1.1.1 Load
Testing
Load testing involves the testing of
the
capacity of a pile by the application of a vertical or horizontal load, or
a combination of both.
The
types of load test may include:
a. Static load test
b. Osterberg load test c.
Lateral load test
d. Dynamic load test
1.1.2 Integrity Testing
Integrity tests involve verifying the soundness of the piles, using methods including:
a. Proof Coring
b. Sonic Logging
c. Vibration Test
d. Modified Shock Test
e. Simple Shock Test
Tests (b) to (e) are non-destructive method and tests (c)
to
(e) are classified as low strain impact test.
Testing may be carried out on preliminary piles or on working piles installed to support
principally vertical loads, or
horizontal loads.
1.2 Related Sections
Read this work section in conjunction with the relevant requirements of the other work sections as follows:
C1-20 Condition Survey and Monitoring
C2-50 Instrumentation and Monitoring
1.3 Standards and Regulations
1.3.1 Standards
Unless otherwise agreed by the SO, ensure all of the Works comply with the relevant requirements of the Standards and Codes listed below or referenced in the body of the Specification. Alternative Standards and Codes may be proposed for approval by the
SO, provided it can be demonstrated that the alternative Standards and Codes comply with the requirements of the standards specified.
All Standards and Codes quoted are
the
current version,
unless specific year references are noted.
Singapore Standards
SS 78: Part
A16 Testing Concrete.
Method
of determination of
compressive strength of
concrete cubes
SS CP 4 Foundations
NPQS
C4-30 Bored Piling Piles
SS CP 79 Safety management system
for construction worksites
Other Standards
ASTM D1143 Standard test method for piles under static axial compressive
load
(ASTM, D1995)
BS 8008 Guide to safety precautions and
procedures for the
construction and descent of machine-bored shaft piling and
other purposes.
1.3.2 Technical References
Refer to the following technical reference for guidance in carrying out the works:
a. BRE Digest
251 (1995) Assessment of damage in low-rise building.
1.4 Trade Preambles
1.4.1 Contractor’s Submissions and Proposals
Engage a PE (civil) to plan, design and supervise any temporary
supports and reaction foundation system
necessary to enable the carrying out of the load tests.
Submit the design to SO for acceptance. All design calculations and drawings are to be
endorsed by the PE.
Propose as a response plan in the event that measures taken to
control ground movement and
vibration do not
perform satisfactorily.
1.4.2 Review and Endorsement of
Test Results
Engage a PE (civil) with relevant experience to review
the
results and interpretation of all
load tests conducted and endorse on all reports submitted.
1.4.3 Building Damage Assessment
Carry out a Building Damage Assessment on the effects of ground movement to
the neighbouring properties due to the works, for the purpose of establishing suitable values for ‘Alert’ and
“Work Suspension’ levels for monitoring. Submit to
SO
with endorsement
from a PE.
1.4.4 Coordination with Other Works
Co-ordinate with other
contractors who may carry out
other works at the same time at the
site. Take
into account of site access, space occupation, safety and safeguarding of
adjoining properties and each other’s works.
1.4.5 Condition Survey
Where applicable, prior to and upon completion of the site works, carry out a condition
survey to
adjacent buildings in
accordance
with
the requirements of
section C1-20 “Condition Survey and Monitoring”. Submit all records to the SO and adjacent property owners where directed.
Keep a copy of the survey report on site ready for inspection.
1.4.6 Instrumentation and Monitoring
Provide instrumentation to monitor the
ground
movement, vibration and condition of
adjacent properties. Refer to Section C2-50, Clause 3.1, and the drawings
for
the schedule of instrumentation required. If necessary or as
required by
the
authorities,
propose and provide additional instrumentation and monitoring for records.
NPQS
C4-30 Bored Piling Piles
Take cognisance of and co-ordinate with other contractors on site who may
be carrying out instrumentation and monitoring works to avoid duplication
of
installation and readings.
For general requirements of the instrumentation and monitoring works refer to Section
C2-50.
1.4.7 Upholding of Adjoining Properties
Accept responsibility for the upholding of the adjoining buildings and roads, footpaths
etc., where applicable, together with the mains and services from the time of taking
possession of the site through the duration of the works.
Adequately maintain roads and footpaths within and adjacent to the site and keep clear of mud and debris.
1.4.8 Existing Services Affected by the Works
Refer to
Preliminaries and
conditions of
contract for
the requirements to
deal
with existing services affected by the works.
1.4.9 Site Protection
Protect all equipment and working area using fencing or other methods as accepted.
1.4.10 Supervision of the Works
Engage a competent and suitably experienced site engineer to the SO’s acceptance, to
supervise the field works.
1.4.11 Quality Control Plan
Submit and work to a quality control plan as agreed with the SO. Refer to the General
Requirements section,
clause 1.4.10 for guidance.
1.4.12 Safety
Provide safety precautions to comply with all current legislation and regulations, notably:
a. Building Control Regulations
b. Code of Practice for Traffic Control at Work Zone
c. Factories (Building
Operations
and
Works of Engineering Construction) Regulations
d. Factories Act
e. SS CP 79 Safety management
system for construction worksites
f. For
works within LTA Railway Protection Zone, ensure the works comply fully
with Code of Practice for
Railway Protection.
Additionally, comply also with the following:
a. BRE Digest
251 (1995) Assessment of damage in low rise building
b. BS 8008: Guide to safety precautions and procedures for the construction and descent of machine-bored shaft
for piling and other purposes
1.4.12.1 Marking of Bores
Ensure that when the pile head is unattended the bore is clearly marked and fenced off at all times.
1.5 Definitions
1.5.1 Allowable Load The load which may be safely applied to a pile after taking into account its ultimate bearing
NPQS
C4-30 Bored Piling Piles
capacity,
negative
skin
friction,
pile spacing,
overall bearing capacity of the ground below
and allowable settlement.
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1.5.2
Compression Pile
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A pile designed to resist compressive axial
force, which would cause it to penetrate further into the ground.
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1.5.3 Constant Rate of Uplift
(CRU) Test
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A test in which the pile is extracted from its position as installed
in the soil at a constant
speed while the
force applied at
the top of the
pile to maintain the rate of uplift is continuously
measured. The force/uplift
relationship
obtained does not
represent an equilibrium
condition between the extractive force and the
uplift.
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1.5.4
Kentledge
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The dead weight structure used in a loading
test.
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1.5.5
Maintained Load
Test
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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.
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1.5.6
Modified Shock Testing
(MST)
|
The computation of the mechanical admittance
of a pile as a function of frequency by Fourier
transform of the signal received by a velocity transducer following a single hammer blow to the head
of the pile.
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1.5.7
Preliminary Test Pile
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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,
dimensions, bearing
capacity and installation method. Preliminary piles
are not expected to
be incorporated into the permanent works
unless otherwise directed.
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1.5.8
Proof Coring
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Coring of the pile shaft from the top of
the pile.
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1.5.9
Working Test Load
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A load applied to a selected working pile to
confirm that it is suitable for the load at the
settlement specified.
A working test
load
should not normally
exceed 200% of the
specified working load on a pile.
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1.5.10
Reaction System
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An arrangement of kentledge, piles, anchors or rafts that provides
a resistance
against which
the pile is tested.
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1.5.11
Raking Pile
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A pile installed at an inclination to the vertical.
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1.5.12
Simple Shock Test (SST)
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The measurement of the frequency response
of a pile to a single hammer
blow.
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1.5.13
Sonic Coring
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Coring through the
tube
provided for sonic
logging.
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1.5.14
Sonic Logging
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The measurement of the travel time of sound
wave from an emitter to a receiver through the
concrete of a pile. The emitter and the receiver
are to be at
the same level generally.
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1.5.15
Tension Pile
|
A pile
designed
to resist tensile axial force,
|
NPQS
C4-30 Bored Piling Piles
which would cause
it to be extracted from the
ground.
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1.5.16
Test Pile
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Any pile to which a test is to be applied.
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1.5.17
Ultimate Bearing
Capacity
|
The load
at which both
the skin and end bearing resistance
of the
soil become
fully
mobilised, or when a total movement of the pile
base equal to 10%
of the base diameter has occurred.
|
1.5.18
Vibration Testing
|
The measurement
of the mechanical admittance of a pile as a function of frequency,
by monitoring the vertical velocity of the pile while it is being excited in the same direction
by a constant force
vibrator being
driven
at
variable frequency
between 20 and5000
Hz.
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1.5.19
Specified Working Load
|
The service load
which the pile is designed to
carry.
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1.5.20
Working Pile
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One of the piles
forming the foundation of a
structure.
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2. PERFORMANCE REQUIREMENTS
2.1 Contractor’s Proposal
When carrying out proposal for temporary supports and reaction systems in clause 1.4.1, ensure that the size, length and number of the
piles or anchors, or the
area
of the rafts,
are
adequate to transmit the maximum test load to the
ground in a safe
manner without
excessive movement or influence on the test pile.
Comply with SS CP4 and other regulations and authority requirements in the design of the foundation for
the
works.
2.2 Pile Testing Requirements
2.2.1 Loading Tests
Plan for and ensure that all load testing are able to verify the loading capacities of the
piles for up to 3 times working load for preliminary test piles, and 2 times working load for
working piles.
Preliminary pile load tests shall be carried out and completed to the satisfaction of the
SO
and meet the specified requirements prior to the commencement of
the actual
permanent piling works.
2.2.2 Integrity Tests
Plan for and ensure that all integrity tests are able to provide sufficient data to verify
the soundness of the installed piles in comparison with specified requirements.
2.3 Permissible Damage Criteria for Existing Critical Structure or
Services
Based on the results of the damage assessment
as set out in Clause 1.4.3, propose the allowable ground settlement and vibration limits due to the works taking into account the
vulnerability and sensitivity of the adjacent properties.
State the values for alert and work suspension levels in the submission in accordance with the requirements of Building Control Act
[Section 7(2)] Annex (BE/CP/5).
Notwithstanding the above, ensure that the
ground movements and vibrations generated by the works comply with the following if more stringent:
Generally comply with the requirements of BS 5228 Part 1.
The vibration generated by the works in MRT structures not to exceed a peak particle velocity of 15mm/s.
Unless otherwise directed, refer to Section C2-50, Clause
4.2.2 for general restrictions on
ground movements and vibration limits for
adjacent structures where relevant.
3. EQUIPMENT
3.1 Calibration
Ensure all testing equipment and
gauges used
for
pile load tests or integrity
tests are
calibrated before and after each test by
SAC-SINGLAS accredited laboratory.
All test equipments are to be calibrated at
a maximum of
six months interval
and calibrations are to remain valid for 2 months at
the time of being used for
the
tests.
3.2 Static Load Test
3.2.1 Equipment
for Applying Load
The equipment used for applying load is to consist of one or more hydraulic rams or jacks.
Check that the total capacity
of the jacks is at least equal to the required
maximum load.
The jack or jacks are to
be arranged in conjunction with the reaction system to deliver an
axial load to the test pile.
The complete system is to be capable of transferring the
maximum load required for the test.
Where kentledge is used, construct the
foundations
for
the kentledge and any
cribwork, beams or other supporting structures in such a manner that there will be no differential
settlement, bending or deflection of an amount that constitutes a hazard to safety or
impairs the efficiency of the operation. Adequately bond, tie or otherwise hold together the
kentledge to prevent it from falling apart, or becoming unstable because of deflection of the supports.
Check that the weight of kentledge is greater than the maximum test load and if the
weight is estimated from the density and volume of the constituent materials, allow
an adequate factor of
safety against error.
3.2.2 Load
Measuring Device
The load measuring device may consist of
a proving ring, load measuring column,
pressure cell or other appropriate
system. Use spherical seating in conjunction with any
devices that are sensitive to eccentric loading; take suitable care to avoid any risk of buckling. Load measuring devices and jacks are to be short in axial length in order to achieve the best possible stability; pay attention to details in order to ensure that axial loading is maintained.
3.3 Osterberg Cell
Load Test Equipment
The equipment is to consist of the following items:
a. Osterberg cell (s)
b. Hydraulics lines and fittings
c. Telltales devices
d. Pressure source and gauge
e. Linear vibrating displacement transducers (LVWDTs)
f. Vibrating wire strain gauges (VWSGs)
g. Reference beam and
digital dial gauges
h. Data Logger
i. Air driven or hand operated hydraulic pump
3.4 Dynamic Load Test Equipment
The equipment
is
to consist of the following items:
a. A hammer of mass (depending on pile size) b.
A pair of strain gauges/transducers
c. A pair of accelerometer d.
A Pile Driving Analyzer
3.5
Sonic Logging Equipment
The equipment is to consist of the following items:
a. A piezoelectric emitter
b. A piezoelectric receiver
and amplifier
c. A drum holding two cables for supply and receipt of signals and with sufficient strength
to support the emitter and receiver, with enough
capacity to accommodate
the
cable required to reach
the
base of any pile to be tested and
calibrated in such a way that there is a measure of the position of the probes within the depth of
the
pile, accurate to ±20 mm.
d. Signal conditioning equipment e. A storage oscilloscope
f. A "Polaroid" camera mounted on the oscilloscope.
Where necessary, Provide means to centralise the probes within the tubes, so that variation in the separation of the
emitter and
receiver resulting from clearance between
the
probes and the tubes does not occur.
3.6 Vibration Test Equipment
The Vibration Test equipment is to consist of the following items:
a. An electrodynamics vibrator
unit with an operating frequency range from about
20Hz to about 2000 Hz.
b. A signal generator c.
A force amplifier
d. A velocity transducer e. A frequency analyser
f. An X-Y plotter
3.7 Modified Shock Test Equipment
The equipment is to consist of the following items:
a. A load cell capable of
measuring a transient force of up to 100kN.
b. A hammer of mass approximately 2 kg.
c. A velocity transducer.
d. A storage oscilloscope.
e. Signal conditioning equipment including a microprocessor
programmed to carry
out a fast Fourier transform on the input signal.
3.8 Simple Shock Test Equipment
The equipment is to consist of the following items:
a. A hammer of mass approximately 2 kg fitted with an electrical triggering device b. A velocity transducer
c. Signal conditioning equipment including an amplifier and filters d.
A storage oscilloscope
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