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A project site in my company is currently working on testing the settlement of our piles using the maintain load test, so my boss is asking me to find out some information on this. In particular, he asked me a) how the maximum allowable settlement is calculated and b) what must be done if the allowable settlement is exceeded.

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The settlement of piles can be determined by conducting a load test. The procedure for the pile load test is as follows ¹:

  1. Preliminary piles shall be tested to not less than twice the working load of the pile or other loads stated in the Contract. Working piles shall be tested to not less than 1.8 times the working load.
  2. Test loads shall be applied and removed in three stages as

Stage Test Load

  • I 25% max. test load
  • II 50% max. test load
  • III 100% max. test load
  1. Unless otherwise permitted by the Engineer, the test loads shall be applied in increments, and removed in decrements, of 25% of the working load. Increments of load shall not be applied until the rate of settlement of the pile is less than 0.1 mm in 20 minutes.

Various types of equipment are required for the determination of settlement of pile foundations. Following is the list of equipment required ¹:

  • Kentledge, anchor piles, or other anchorages supported or installed at suitable locations to provide adequate reactions against jacking.
  • A load-measuring device which shall consist of a load column, pressure cell, or other appropriate system, calibrated before and after each series of tests, or whenever adjustments are made to the device, or at time intervals recommended by the manufacturer of the equipment.
  • Four deflectometers accurate to 0.025 mm.
  • Precision leveling equipment accurate to 0.25 mm.
  • A reference frame for supporting deflectometer and providing a datum for deflectometer measurements.
  • Working platforms.
  • Screens and protection from exposure to conditions that may affect the test.
  • Hydraulic loading equipment.

The allowable limit on settlement of an individual pile during load tests is around 10mm at working loads ². If the allowable settlement is exceeded, the engineer may ask for 1.5 times that settlement at 1.5 times the working load to ensure elasticity. If the allowable settlement is exceeded, the engineer may need to re-evaluate the foundation design and consider remedial measures.

The Images are in reference to the Borj Khalpha project.

load testing borj al khalife borj khalipha

(1) Determination of Piles Settlement by Load Test - The Constructor. https://theconstructor.org/geotechnical/determination-of-piles-settlement-by-load-test/7389/. (2) Bored Piles Design: geotechnical considerations - Ingeoexpert EN. https://ingeoexpert.com/en/2021/07/06/bored-piles-design-geotechnical-considerations/. (3) Pile Load Test | Purpose of Pile Load Test - Engineering Projects. https://bestengineeringprojects.com/pile-load-test/. (4) PILE TESTING SPECIFICATION FOR DRIVEN PILES - G & P. https://gnpgroup.com.my/wp-content/uploads/2017/03/SP006.pdf. (5) Numerical and Theoretical Study on the Settlement of Capped Piles .... https://downloads.hindawi.com/journals/ace/2020/3978780.pdf. (6) Pile Load Testing for Bored Piles in Soil - STRUCTURE mag. https://www.structuremag.org/wp-content/uploads/2021/05/282106-C-StructuralFoundations-Ng.pdf.

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  • $\begingroup$ What are some of the remedial measures taken in the case of failure? $\endgroup$ Nov 15, 2023 at 3:52
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    $\begingroup$ redesign the foundation. these are pre-construction tests just to determine if the foundation is strong enough. $\endgroup$
    – kamran
    Nov 15, 2023 at 5:26
  • $\begingroup$ What about improving the soil via compaction/grout? $\endgroup$ Nov 15, 2023 at 6:01
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    $\begingroup$ I guess there are techniques to do that, but I am not sure if it is practical. I am not aware of any remedial work on the big projects. I myself had a job that called for a small pocket of bad soil to be excavated and replaced with designed fill. but that was because the strata underneath were competent. and we did not load test any caissons. they had drilled test holes and had the profile of the site. $\endgroup$
    – kamran
    Nov 15, 2023 at 7:23

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