Vertical and Lateral load tests shall be carried out for piles as per procedures laid down in IS: 2911 Part-4 – 1985. The bearing capacity of a single pile shall be determined from test loading a pile. The load test on a concrete pile shall not be carried out earlier than 28 days from the time of casting of the pile. The test pile head shall be prepared one week after casting the pile.
Initial/Routine Pile load Test:
Initial load tests shall be carried out on test piles to assess the safe load carrying capacity of the pile before start of installation of working piles. Routine load tests shall be carried out to verify the load capacity of working piles. This shall include the following type of tests:
- Vertical (compression) load test to assess vertical load capacity
- Lateral load test to assess lateral load capacity
Vertical Load test
In this type of test. compression load is applied to the pile top by means of a hydraulic jack against rolled steel joist or suitable load frame capable of providing reaction and the settlement is recorded by suitably positioned dial gauges.
- The Pile head should be prepared firstly by chipping of pile till the sound concrete is met. The projecting reinforcement should be cut off or bent suitably and the top finished smooth and level.
- Load test shall be carried out by direct loading method by applying a series of vertical downward incremental load. Each increment shall be about 20% of the ultimate carrying capacity of the pile.
- In case of initial load test, applied load reaches 3 times the safe vertical load carrying capacity or maximum settlement of pile exceeds a value of 10% of pile diameter.
- In case of routine load test, applied load reaches one and half times the safe vertical load carrying capacity or the maximum settlement of test loading in position attains 12mm.
Lateral Load test
The Purpose of Routine Lateral Load Test is to verify the Safe Lateral Load Capacity of Working Piles installed. Routine Lateral pile load test shall be conducted on Test Pile as per I.S. 2911 (PART 4)-2013 CODE OF PRACTICE FOR DESIGN AND CONSTRUCTION OF PILE FOUNDATION PART 4 LOAD TEST ON PILES.
Test Set-up for Routine Lateral Pile Load Test:
- For Test, the Pile shaft shall be finished smooth by chipping off uneven concrete of the side of the Pile as far as practicable.
- A bearing plate at the Test Pile shaft shall be fixed for the Jack to give reaction.
- For applying the load, Hydraulic jack with calibrated pressure gauge and pump shall be used.
- The reaction shall be taken from the 1 Nos. Working Piles as Support Piles. A Concrete Block shall be lowered reacting against the Support Piles and jack shall be inserted reacting against the test Pile and other working pile with suitable packing (if required).
- To record the settlements, one Dial Gauges of 0.01 mm sensitivity shall be positioned in the opposite direction of Jack to measure the displacement directly in case of load shall be applied at cut-off level; In case of unapproachable cut-off levels, displacements shall be read by using at least two dial gauges of 0.01 mm sensitivity spaced at 30 cm and kept horizontally one above the other on the working pile (test pile) and the displacement shall be interpolated at cut-off level from similar triangles.
- The dial gauge shall be held by magnetic holder attached to Datum bar which shall be resting on immovable support.
Test Procedure for Routine Lateral Pile Load Test:
a. The test shall run in general as per procedures laid down in I.S. 2911 (PART-IV)-2013.
b. The pressure gauge of Jack and Dial Gauges shall be set to zero before application of any load.
c. The load shall be applied in increment of about 1/5 of the Safe Load and shall be maintained till the rate of displacement / deflection is less than 0.1 mm per 30 minutes.
d. Final Test load shall be unloaded in the same decrement and rebound shall be recorded at the intervals of 15 minutes.
Pile Integrity Test
Low strain integrity testing (PIT) of Pile shall be done for checking the integrity of piles. The testing involves attachment of accelerometer on a prepared pile top. After attachment, the impact device (hand held hammer) generates a low strain compression wave, which travels down the pile. The
acceleration and velocity records of the impact, along with subsequent form either pile toe/discontinuities are graphically displayed.