i) Plate load test is a filed test to determine the ultimate bearing capacity f soil and probable settlement under given loading.
ii) The test essentially consist in loading a rigid plate, called bearing plate at the foundation level and determining the settlement corresponding to each load increment.
iii) The ultimate bearing capacity is taken as the load at which plate starts sinking at a rapid rate.
iv) The test pit having width equal to 5 times the width of bearing plate is dug upto a depth of proposed foundation. Plate size may vary in width from 300 mm to 750mm and 25 mm thick.
v) The loading to the test plate may be applied with the help of a hydraulic jack. The reaction of hydraulic jack may be borne by either of following two methods
a) By gravity loading platform methods.
b) By reaction truss method
vi) In the case of gravity loading method, a platform is constructed over a vertical column resting on the test plate and the loading i done with the help of sand bags, stones or concrete blocks.
vii) When the load is applied to the plate, it sinks or settles. The settlement of plate is measured with the help of sensitive dial gauge and for square plate two dial gauge.
ix) The dial gauges are mounted on independently supported datum bar. As the plate settles, the ram of the dial gauge moves down and settlement is recorded. The load is indicated on the load gauge of the hydraulic jack. Load is applied in increment of 1/10 th of estimated failure load.
x) Settlement readings are made at regular instead of 1,2,5,10,20,40 & 60 minutes.
Until the rate of settlement becomes less than about 0.02 mm/hr
xi) the results of test are plotted between settlement and load intensity