Laboratory and Field Testing

Plate bearing testing

The plate bearing test (also known as plate loading test) is used to determine the ultimate bearing capacity of the ground and the likely settlement under a given load.

The results of the plate bearing test are applied in the design of temporary working platforms for piling rigs or pads for crane outriggers. An approximate equivalent CBR value can 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 720mm 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. The test requires a large reaction load, like a tracked excavator or other suitable construction plant.

Our engineers will advise on the plate diameter required to match the anticipated design load and reaction load (size of the excavator) to be made available for us on site. We will typically complete four to six tests in a day subject to site conditions and can provide you with the results the following day.