Pile Load Tests

1 INTRODUCTION

Load tests are conducted to evaluate the bearing capacity of pile. The

design engineers recommend to make a test pile when a massive pile construction job takes place. This pile is subjected to the load test.

The load test may be categorized as below.

1. Initial test.

2. Routine test.

Initial test is carried out on test piles while the Routine test is carried

out as a check on working piles and to estimate the displacement corresponding to the working load.

Initial test is a very important test and it is the basis for the following-

1. To establish settlement at working load.

2. To establish criteria for installation of working piles.

3. To check the suitability of a pile designed for a particular cause.

4. To estimate the safe load capacity of the pile.

IS: 2911.(Part IV)-1979 recommends the minimum of two initial tests for

a sizable work of more than 200 piles. For routine tests, the minimum

number of tests should be half percent. The field engineer may ascertain

the number of tests up to 2 percent or even more if the soil strata is varying in nature. For the important structures also, the number of tests may

be up to 2 percent. However this number may very.

The tests may be carried out on a single pile or group of piles as required. The loads are applied in series over a RCC cap on the piles. Figure 1

shows the typical set up for pile load test.


2 PREPARATION OF PILE FOR TEST (IS: 2911 (Part IV))

I. For compaction piles, group tests should be normally done on a

group of piles with their cap resting on ground.

2. In case a portion of the pile is likely to be removed or exposed later

due to scour, dredging or otherwise, then the capacity contributed

by the portion of the pile during load tests shall be duly accounted

for. The pile groups in the above conditions shall be tested without

their cap resting on the ground.

3. The tests should be carried out at cut-off level, wherever applicable.

Otherwise the suitable allowance shall be made in the interpretation

of test results/test load if the test is not carried out at cut-off level.

4. For cast-in-situ piles , the test should be conducted after the concrete

had gained its strength. The test should be conducted after minimum

28 days after casting. This may be less in case of rapid hardening

cement.

5. The pile head should be chipped off carefully tills ound concrete is

met. The projecting reinforcement should be cut-off or bent suitably

and the top finished smooth and level with plaster of paris when

required. For the jacks to rest, a bearing plate should be placed on

the head of the pile.

5.3 INITIAL TEST

The load is applied by means of a hydraulic jack with pressure gauge and

remote control pump acting against rolled steel joists obtaining the reaction

from the following.

(a) Kentledge heavier than the required test load placed on a platform

supported clear of the test pile. The center of ·gravity of the kentledge

and the load applied by the jack should be coaxial with the pile.

(b) Anchor piles or other suitable anchors. The center to center distance

between the test pile and anchor pile should be minimum 5 times

the test pile shaft diameter.

The test load should be applied in increments of about 20 per cent of the

assumed safe load. The reaction to be made available for the test should

be 25 percent more than the final test load proposed to be applied. The

settlements are recorded by four dial gauges of 0.02 mm sensitivity each

positioned at equal distances around the piles and normally held by datum

bars resting on immovable supports at least 5 D (subject to a minimum of

1.5 m) away from the test piles periphery (D being the pile stem diameter

in case of circular piles or diameter of circumscribing circle in case of

square piles).


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