Q. Explain Plate loading test?
In general iron plates either 60 cm squares or 75 cm dia and 16 mm thick are used, size of plate should not be less then 1/5th of the width of foundation trench, where the test plate is to be placed on the surface. It is preferably to remove the top 23 cm of natural soil before placing the plate. It is very important to seat the plate accurately over the area and the ground should be leveled as much as possible. The plate should be rotated over the area and any irregularities over the surface trimmed off. The plate should be in contact with the soil over all its area on coarsely grained soil over which are difficult to level accurately. The plate can be seated on the layer of fine dry sand 6 mm thick. The load can be applied to the test plate.
The following methods may be adopted -
Load the soil four times the proposed design load and read settlement every 24 hours until no settlement occurs in 24 hrs. Add 50% more load and read settlement in every 48 hrs until no settlement occurs in 48 hrs. Settlement under the test load should not show more than 20 mm or increment of settlement under test load. If the above limitations are not met, repeat the test with reduced load will be taken for the safe loading capacity of the soil. At least two tests should be carried out preferably with different size of plates.