Our geotechnical team have been hard at work in London this week carrying out a plate load test. A plate load test (sometimes known as a plate bearing test) is an in-situ test performed to assess the ground’s ability to withstand a specific pressure. From this we are able to determine the likelihood of any movement or settlement. The test is typically used in situations where there will be a temporary load applied to the area in question, for example a crane, piling rig or working platform. In cases where the underlying ground conditions are too granular, it is possible to calculate an equivalent CBR (California Bearing Ratio) value for a standard CBR test to be completed.
The plate load test is completed by pushing a steel plate of a set diameter (typically 300mm, 450mm or 600mm) against the material concerned. This is commonly accomplished using a hydraulic cylinder kit varying from 0-60 tonnes capacity with an in-line gauge. A sufficient deadweight must be used, a heavy excavator is common for this purpose. The weight of the excavator will depend on the design load required and the size of bearing plate in use. To guarantee safety, British Standard BS1377: Part 9:1990 requires that the pressure applied during the test is the equivalent of three times the working pressure the planned temporary structure will apply.
Settlement of the bearing plate is measured over set increments of load. By plotting the pressure against plate settlement, the likely immediate ground settlement can be calculated, alongside further useful parameters.
If an equivalent CBR value is required, readings are taken at 5 increments between 0 and 1.5mm and then plotted against the load achieved. This value can be calculated to a 1.25mm displacement by using a simple mathematical formula.
For more information on Plate Load and CBR testing, click here. To find out about the other geotechnical services we offer, click here. If you need a Plate load or CBR test, or you wish to discuss your requirements with a qualified geotechnical engineer, contact us.
