In this article, we will discuss the load test method used for determining the settlement of pile foundations. This method involves certain equipment and procedures that we will also cover. Additionally, we will go over the reporting of results.
To determine the settlement of pile foundations, the load test method is commonly used. This method requires specific equipment to carry out the test, which we will discuss shortly. The procedure for this test is also important, and we will outline it in detail. Finally, the results obtained from the load test must be reported accurately, and we will discuss how to do so.
Overall, this article will provide a comprehensive overview of the load test method for determining the settlement of pile foundations. It will cover the necessary equipment and procedure, as well as the reporting of results.
Equipment for Pile Settlement Determination Test
In order to determine the settlement of pile foundations, several types of equipment are required. These include a Kentledge or anchor piles, which provide adequate reactions against jacking at suitable locations. A load-measuring device is also needed, which consists of a load column, pressure cell, or other appropriate system that is calibrated before and after each series of tests, or at recommended time intervals by the manufacturer of the equipment.
Four deflectometers are necessary for accurate measurements, which should be accurate to within 0.025 mm. Precision levelling equipment, accurate to 0.25 mm, is also required. A reference frame is needed to support the deflectometers and provide a datum for measurements. Working platforms are necessary, as well as screens and protection from exposure to conditions that may affect the test. Finally, hydraulic loading equipment is required to complete the testing process.
Procedure of Pile Settlement Determination Test
The procedure before testing shall be as follows:
The installation of anchorages such as kentledge and anchor piles is required before conducting a pile test. The centre of each anchor pile should be located at a distance of at least 2 meters or three times the pile diameter, whichever is greater, from the centre of the pile being tested and from the centre of any adjacent pile.
In case the pile being tested needs to be extended from cut-off level to ground level, it must be ensured that the strength of the pile at joints is not less than any normal section of the pile.
A temporary square pile cap designed by the Contractor must be constructed, and appropriate working platforms, screens, and protection should be installed before beginning the pile test.
To measure the deflection of the four corners of the temporary pile cap, a reference frame should be set up on supports that are at least 2 meters or three times the pile diameter, whichever is greater, from the test pile and anchor pile. The four deflectometers should be mounted on the reference frame.
Fig: Pile load test for Burj Khalifa (Dubai)
Procedure: Pile Load Test
The procedure for the pile load test shall be as follows:
The testing of preliminary piles and working piles is subject to certain requirements as outlined in the contract. Preliminary piles must be tested to at least twice the working load, while working piles must be tested to not less than 1.8 times the working load. Group or boundary effects should not be taken into account when determining test loads.
The application and removal of test loads should be done in three stages as specified in Table-1. Test loads should be applied in increments of 25% of the working load unless otherwise instructed by the Engineer. These increments of load should not be applied until the rate of settlement of the pile is less than 0.1 mm in 20 minutes.
During Stage I loading, the full test loads should be applied in increments and maintained for at least 24 hours after the rate of settlement has reduced to less than 0.1 mm per hour. The test loads should be removed in decrements, and the recovery of the pile should be determined before loading resumes.
The same procedure used in Stage I loading should be followed in Stage II loading. Additionally, the procedure outlined in Stage I should be repeated in Stage III loading unless the Engineer instructs otherwise.
Throughout the test, the settlement of the pile should be measured at hourly intervals, or at other intervals agreed upon by the Engineer. Settlements should be measured and times recorded in the presence of the Engineer. The level of the reference beam should also be checked at regular intervals agreed upon by the Engineer during the test.
Table – 1: Test loading stages
| Stage | Test Load |
| I | 25% max. test load |
| II | 50% max. test load |
| III | 100% max. test load |
Procedure: after testing
After conducting testing, it is required to remove the equipment used for the testing. This includes the temporary pile caps and the pile extensions that were added to the piles during the testing process. The removal of these components should be done in a way that ensures they are cut off at the appropriate level.
If there are anchor piles that were used during the testing process, they must be withdrawn unless the Engineer permits otherwise. It is important to follow the Engineer’s instructions in this regard.
It is crucial to ensure that the removal of all equipment and components is done safely and effectively. Any damage that may be caused during the removal process should be avoided to prevent any potential safety hazards or further repairs. Overall, proper removal of the equipment and components used during the testing process is essential to ensure the safety and stability of the site.
Reporting of Test Results
The report should include detailed information on four aspects: the loads applied, settlement of the pile, timing of loading increments and decrements, and levels of the reference beam. For the loads applied, the measurement should be accurate to the nearest 0.05 t. This information is critical in understanding the amount of force applied to the pile during the testing period.
The settlement of the pile should also be reported at hourly intervals, with measurements accurate to the nearest 0.05 mm. Additionally, the settlement should be recorded under each increment and decrement of loading, which will help identify any changes or trends in the pile behavior during the test.
The report should also include the exact times at which increments were applied and decrements removed. This information will help researchers understand how the pile reacted to each load and how long it took to settle after each increment or decrement.
Finally, the levels of the reference beam should be recorded, with measurements accurate to the nearest 0.05 mm. This information will help ensure that any settlement measured in the pile is not due to movement of the reference beam itself.
Overall, a thorough and detailed report including all of these elements is crucial for accurately interpreting the results of the pile testing and drawing conclusions about the pile’s behavior under load.