Static Load Pile Test Method Statement Template.
In previous articles we explain High Strain Dynamic Pile Test Method Statement, Mechanical Caliper Logging Test and Cross Hole Sonic logging Test. Now we will explain Static Load Pile Test Method Statement.
1. GENERAL.
This test method covers the procedure for testing vertical
pile to determine response of the pile to a static compressive load applied
axially to the pile. Two principal types of test are used for compressive
loading on piles.
The first of these is the constant rate of penetration (CRP)
test, in which the compressive force is progressively increased to cause the
pile to penetrate the soil at a constant rate until failure occurs.
The second
type of test is the maintained load (ML)
test in which the load is increased in stages to some multiples, say 1.5 times or twice the working
load with the time- settlement curve
recorded at each stage of loading and unloading load.
The ML test may
also be taken to failure by progressively increasing the load in stages. This
test method is applicable to all deep foundation units regardless of their size
or method of installation.
2. SIGNIFICANCE AND USE.
A loading test on a
pile is made for the purpose of finding the settlement to be expected at the
estimated working load, or some multiple thereof determining the ultimate bearing
capacity, or checking the structural soundness of the pile. A relation between settlement
and load for a pile may be obtained.
3. APPARATUS.
3.1 Data Logger.
The data from the strain gauges will be recorded by using a
Data Logger model no. DT
85, manufactured by “DATATAKER PTY. LTD. AUSTRALIA”.
3.2 Displacement Transducers.
The displacement transducers shall be connected to digitally
measure the pile head
movement during execution of static axial compression
test.
3.3 Load Cells.
A load cell is a transducer that is used to convert a force
into electrical signal.This
conversion is indirect and happens in two stages. Through a
mechanical arrangement, the
force being sensed deforms a strain gauge.
The strain gauge
converts the deformation (strain) to electrical signals. A load cell usually consists
of four strain gauges in a Wheatstone bridge configuration.The electrical signal
output is typically in the order of a few millivolts. The output of the transducer is plugged into
an algorithm to calculate the force applied to the transducer." The Load Cell shall
be connected to the data logger to digitally record the applied load transfer to the pile head
by hydraulic jack.
4. PROCEDURE.
4.1 General.
Applicable project information shall be reviewed and
recorded prior to test, including soil boring logs, pile installation records
and concrete properties.
4.2 Preparation of the Test Pile.
Where feasible, the immediate area of the test pile shall be
excavated to the proposed pile cut-off elevation. The pile head should be cut
off or built up to necessary elevation and should be capped appropriately to
produce a bearing surface perpendicular to the axis of the pile.
4.3 Test Setup.
4.3.1 Load Applied
to Pile by Hydraulic Jack Acting against Anchored Crown Reaction Frame.
The reaction system for all compression test pile will be
provided by the ground
Tie back anchors shall be installed for the static
compression load test setup in order to provide reaction to the loading system.
Loads on each anchor and its dimensioning are made as elaborated in the
design.
A powerful anchoring machine shall be used to install the
tie back anchors; following sequence shall be adopted for the installation of
the anchors.
a. Install the anchor machine at approximately the same
level of the anchor head. Adjust the
swing mast to the required inclination to meet the design/site
requirements.
Note: The anchoring
machine mast can be rotated in all directions to accommodate the site requirements.
b. Temporary steel casing shall be drilled through the soil
with the help of its
water flush system.
In order to prevent any escape of soil while drilling, the casing shall
be provided with an end plug.
Extreme care shall be taken to avoid any damage of
underground structures while installing the anchor. In case of existence of any obstructions such
as pile foundations, the direction of the anchors can be shifted to any
adjustable mast if anchoring machine or the position of the anchor itself can be
relocated.
After reaching the required anchor length, ready made anchor with grout pipe at the middle will be inserted into the casing. The temporary casing shall be withdrawn whilst filling the bore with primary cement grout. The grout will carry on until the grout has replaced the water in hole completely.
5. LOADING PROCEDURE.
5.1 Loading Schedule.
Unless failure occurs first, apply, and remove a total test
load equal to the specified anticipated pile design load with adequate safety
factor, applying the load in increments of 25% of the individual pile design
load.
Maintain each load increment until
the rate of settlement is not greater than 0.25 mm⁄h but not longer than 2 h. Provided that the test pile has not
failed, remove the total test load any
time after 12 h if the butt settlement over a one hour period is not
greater than 0.25 mm; otherwise allow the
total load to remain on the pile for 24 h.
After the required holding time,
remove the test load in decrements of 25% of the total test load with 1 h
between decrements.
6. TAKING
MEASUREMENTS . 6.1 Standard Measuring Procedures.
Take and record readings of time, load, and movement
immediately before and after the application of each load increment and the
removal of each load decrement. During loading, provided that the test pile has
not failed, take additional readings, and record them at intervals not
exceeding 10 min during the first ½ h and 20 min thereafter for each load
increment.
After the total load has been
applied, provided that the pile neither has nor failed, take readings and record at intervals not exceeding 20 min
during first 2 h, not exceeding 1 h for the
next 10 h, and not exceeding 2 h for the next 12 h.
If pile failure
occurs, take readings immediately before removing the first load decrement.
During unloading, take readings and record at intervals not exceeding 20 min.
Take a final rebound reading at 12 h after all load has been removed.
7.0 TEST REPORT REQUIREMENTS.
- Project identification/location.
- Identification (name and designation) of test pile(s).
- Working load and safety factor (or required ultimate capacity) of the pile(s).
- Type and dimensions of pile(s) including nominal or actual cross-sectional area, or both length and diameter (as a function of pile length for timber of composite piles).
- Description of all components of the apparatus for obtaining measurements
- Date tested.
- Date casted.
- Test pile identification.
- Graphical presentation of Time – Load – Settlement and Load – Settlement.
8.0 REFERENCES.
Standard Test Method
for Piles Under Static Axial Compressive Load - ASTM D1143 BS 8004: 1986.