The plate load test is used to determine the ultimate bearing capacity of the ground and the likely settlement under a given load.This test is very popular for selection and design of shallow foundation. The results of the plate load test are also applied in the design oftemporary working platforms for piling rigs or pads for crane outriggers. An approximate equivalent CBR value can also be derived from the modulus of subgrade reaction.
The test involves loading a steel plate of known diameter and recording the settlements corresponding to each load increment. The test load is gradually increased until the plate begins settling at a rapid rate. The total value of the load on the steel plate divided by the area of the plate gives the value of the ultimate bearing capacity of the soil. A factor of safety is applied to provide the safe bearing capacity.
The plate bearing test is typically carried out at foundation level, either on the surface or in a shallow pit. Plates of varying sizes up to 1000mm diameter are available. The loading plate is placed on the ground and connected via a load cell to a reaction load.Due to the larger size of the plate used (compared with a CBR test) this procedure is more suitable for testing aggregate backfills.