This method statement for static load pile testing covers the procedure for testing vertical piles to determine their response to static compressive loading.
What is a static pile load test?
A static pile load test is performed to measure how a pile behaves under an applied load.
This pile load test method describes how to test vertical piles to see how they react to static compressive loads that are applied axially to the pile. Compressive loading on piles is tested using two main categories.
The first of these tests is called the Constant Rate of Penetration (CRP) test, in which the compressive force is gradually raised to make the pile continuously penetrate the soil up until failure.
The Maintained Load Test Procedure is the second type of test, in which the load is gradually increased to a multiple of the working load, such as 1.5 times or twice that amount, with the time-settlement curve being recorded at each stage of loading and unloading load.
By gradually raising the load, the Maintained Load (ML) test can likewise be performed until it fails. No matter how big or how they were installed, all deep foundation units must pass this test.
2. Use and Significance
A pile is subjected to a loading test in order to determine the settlement that can be anticipated at the estimated working load, or some multiple thereof, as well as the pile’s ultimate bearing capacity and structural soundness. For a pile, a relationship between settling and load can be found.
3.1 Data logger
A Data logger will be used to record the strain gauge data.
3.2 Transducers for displacement
When performing a static axial compression test, the displacement transducers must be connected in order to digitally measure the pile head movement.
3.3 Load Cells
A transducer called a load cell is used to transform a force into an electrical signal.
This conversion takes place in two steps and is indirect. A strain gauge is deformed by the force being measured through a mechanical setup.
The deformation (strain) is converted to electrical impulses via the strain gauge. Four strain gauges are often arranged in a Wheatstone bridge configuration to form a load cell. The electrical signal output typically ranges from a few millivolts to a few volts. To determine the force exerted on the transducer, the output of the transducer is entered into an algorithm. ” To digitally record the applied load transfer from the hydraulic jack to the pile head, the load cell must be linked to the data logger.
4. Procedure for Pile Load Test
Before a test, relevant project data, such as soil boring logs, pile installation records, and concrete qualities, must be examined and recorded.
4.2 Making the test pile ready
The test pile’s immediate surroundings should, whenever practical, be excavated to the proposed pile cut-off elevation. To create a bearing surface perpendicular to the pile’s axis, the pile head should be removed or raised to the required elevation and capped.
4.3 Compression Load Test Setup
4.3.1 Hydraulic jack acting against anchored crown reaction frame to apply load to pile
The ground anchors attached back to the crown will serve as the response system for all compression test piles.
In order to react to the loading system during the static compression testing setup, tie-back anchors must be fitted. Each anchor’s load and dimensioning are constructed according to the design’s detailed specifications.
The tie-back anchors must be installed using strong anchoring equipment, and the procedure described below must be followed.
Install the anchor machine at a level that is roughly equal to the anchor head. To fulfill the needs of the design and the site, adjust the swing mast to the desired inclination.
The anchoring machine mast can be adjusted to fit the needs of the site in any direction.
A temporary steel casing with a water flush system must be drilled into the ground. The casing must have an end plug in order to stop any soil from escaping while drilling.
While installing the anchor, extreme caution must be exercised to prevent any damage to underground structures. The orientation of the anchors can be changed to any adjustable mast if an anchoring machine is present, or the location of the anchor itself can be changed, in the event that there are any obstructions present, such as pile foundations.
The ready-made anchor with the grout pipe in the middle will be put into the casing once it has reached the necessary anchor length. While primary cement grout is being used to fill the bore, the temporary casing must be removed. The grout will continue to fill the hole until all of the water has been replaced by grout.
5. Loading method
5.1 Loading plan
Apply and remove a total test load with a sufficient safety factor that is equal to the anticipated pile design load, unless a failure occurs before. Apply the load in increments of 25% of the individual pile design load.
Keep adding loads until the rate of settlement is less than 0.25 mm per hour but not more than 2 hours. If the test pile hasn’t failed, remove the entire test load at any point after 12 hours if the butt settlement over an hour is less than 0.25 mm; otherwise, let it stay there for 24 hours.
Remove the test load in increments of 25% of the total test load after the appropriate holding period, with 1 hour separating each increment.
5.2 Maximum test load
A 10% to 20% margin is allowed on the capacity of the reaction against the maximum test load.
6. Measurements logging
6.1 Standard measuring techniques
Before and after applying each load increment and removing each load decrement, measure the duration, load, and movement and record the results. If the test pile has not failed, take additional readings during loading and record them at intervals no greater than 10 minutes for the first 12 hours and 20 minutes after that for each load increment.
Take readings and record them at intervals of no more than 20 minutes for the first two hours, no more than one hour for the following ten hours, and no more than two hours for the following twelve hours after the complete load has been applied, assuming the pile has not failed.
Take readings right away before eliminating the first load decrement if a pile failure occurs. Take readings while unloading and record them every 20 minutes or less. 12 hours after the last load has been lifted, take a final rebound reading.
7.0 Requirements for Test Reports
Project name & location
Identification of the test pile (name and designation).
Working load and the pile’s safety factor (or necessary ultimate capacity).
Report and recommendations on the ultimate pile capacity.
Including a nominal or actual cross-sectional area, or both length and diameter, depending on the type and dimensions of the piles (as a function of pile length for timber of composite piles).
A description of every element of the measurement equipment
Identification of a test pile.
Time-Load-Settlement and Load-Settlement are presented graphically.
8.0 Resources for Method Statement for Static Load Pile Testing
ASTM D1143 BS 8004: 1986 Standard Test Method for Piles Under Static Axial Compressive Load
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