Plate Bearing Test

The Plate Bearing Test, also known as the Plate Loading Test, is an in-situ method for determining the ultimate bearing capacity of the ground and the potential settlement under a given load. This test is particularly useful for the design of temporary working structures such as piling platforms or crane outrigger pads.

The test is typically used for site investigations to evaluate the strength and variability of near-surface ground conditions which are critical for the design and operation of working platforms. The results of the test can also provide approximate equivalent CBR values using a mathematical relationship.

The test is carried out in accordance with the British Standard BS 1377 Part 9: 1990. It involves loading a steel plate of a known diameter and measuring the corresponding settlements at each load increment. The load is gradually increased until the plate starts to settle at a rapid rate. The ultimate bearing capacity of the soil is determined by dividing the total load on the plate by the area of the steel plate. A factor of safety is then applied to give the safe bearing capacity of the soil.

The Plate Bearing Test is usually conducted at foundation level, either on the surface or in a shallow pit. The loading plate is placed on the ground and connected to a reaction load via a load cell. Due to the larger size of the plate used, this test is more suitable for testing larger aggregate backfills, but it requires a larger reaction load. Typically, a minimum of a 15-tonne tracked excavator or other suitable equipment is needed for the reaction load.

It is important to consult with a professional engineer to determine the appropriate plate diameter and reaction load for the anticipated design load. On average, 3-7 tests can be completed in a day, depending on site conditions, and the results can typically be provided the following day.