Pile Maintain Load Test (MLT)

PILE MAINTAIN LOAD TEST (MLT)

Maintain Load Test

Maintain Load Test, MLT (also known as a Static Load Test) is essential to confirm that the installed pile can safely bear the building or structure’s design load. During this test, a load is applied to a selected pile, and the resulting settlement is recorded. Typically, the test load is twice the working load of the pile.

Pre-Test Preparations:

Before testing, the pile head must be cut or built up to the required elevation and properly capped to create a bearing surface perpendicular to the pile axis. The setup should ensure that no part of the test load is transferred to the ground beneath the cap.

Methods of Applying the Test Load:

The test load can be applied using one of the following methods:

  1. Kentledge Method:
    • A hydraulic jack uses reaction forces from a kentledge stack heavier than the required test load.
    • Ensure the center of gravity of the kentledge aligns with the pile axis. The nearest edge of the crib supporting the kentledge must be at least 1.3 meters from the test pile.
    • Kentledge should not be used for raked piles.
  2. Anchor Piles Method:
    • A hydraulic jack applies force, obtaining its reaction from tension piles or suitable anchors.
    • Anchor piles must be at least three times the pile shaft diameter away from the test pile (center-to-center) and no less than 2 meters.
    • If anchor piles are part of the permanent structure, their levels should be monitored during testing to prevent residual uplift.

Load Measurement:

  • Use calibrated load and pressure gauges in the hydraulic system.
  • Ensure the jack and load gauge are aligned to apply the load co-axially.

Settlement Measurement:

  • Settlement is measured using a reference beam or wire, independent of the load test pile and reaction piles.
  • Accuracy:
    • Reference beams: Measure to the nearest 0.1 mm.
    • Reference wires: Measure to the nearest 0.5 mm.
  • Supports for reference beams must be at least 3 meters from the test pile and protected from temperature changes.

Test Procedure:

Unless specified otherwise by consultants, the Maintained Load Test follows these steps:

a) Loading Sequence:

  • Apply the full test load (twice the design load) in twelve equal increments.
  • Wait at least two hours between increments or until the settlement rate is less than 0.25 mm/hour.

b) Full Load Maintenance:

  • Maintain the full test load for at least 48 hours.
  • Record settlements at intervals of no more than 12 hours.

c) Unloading Sequence:

  • Unload in four equal decrements at one-hour intervals.
  • Take settlement readings immediately before and after each load change.

Maintain Load Test