Limitations
Since a plate load test is of short duration, consolidation settlements cannot be predicted. The test gives the value of immediate settlements only. If the underlying soil is sandy in
nature immediate settlement can be taken as total settlement. If the soil is of clayey type, the immediate settlement is only a part of the total settlement. Load tests, therefore do not have much significance in clayey soils to determine allowable pressure on the basis of settlement criterion.
Plate load test results should be used with caution and the present practice is not to rely too much on this test. If the soil is not homogenous to a great depth, plate load tests give very misleading results.
Plate load tests is not at all recommended in soils which are not homogenous at least to a depth equal to 1.5 to 2 times the width of the prototype foundation.
Plate load tests should not be relied on to determine the ultimate bearing capacity of sandy soils as the scale effects give misleading results. However, when the tests are carried on clay soils, the ultimate bearing capacity as determined by the test may be taken as equal to that of the foundation since the bearing capacity of clay is essentially independent of the footing size.
The plate load test is possibly the only way of determining the allowable bearing pressures in gravelly soil deposits. For tests on such soil deposits the size of the plate should be bigger to eliminate the effect of grain size. |
