Services / California Bearing Ratio (CBR)

The California Bearing Ratio (CBR) is an essential parameter in the design of roads / hardstanding. An accurate value will allow a cost-effective design.


Geotest can carry out four types of test:


  • Dynamic Cone Penetrometer (DCP) – The DCP test measures equivalent CBR over a range of depths, typically up to 1m. This has the benefit of avoiding the need for an excavator on many sites, and allows an ‘optimum depth’ to be established. The test is rapid (typically around ½ hour), and can be undertaken in cohesive or granular materials.
  • Mexe Cone Penetrometer – Developed in conjunction with the Ministry of Defence, the Mexe Cone Penetrometer is a lightweight, reliable probe that allows a rapid measurement of CBR in fine grained soils. The test measures CBR over a range of depths up to 0.8m. This has the benefit of avoiding the need for an excavator on site, and tests can be carried out in just a few minutes.
  • Plate Bearing Tests (PBTs) – California Bearing Ratio (CBR) can be calculated from the Plate Bearing Test (PBT). This test is very accurate and has the added benefit of providing an indication of ground bearing pressure at the same time.
  • Clegg Impact Soil Tester (CIST) – Popular with local authority, the Clegg Impact Soil Tester is both accurate and rapid. The test is typically carried out at the ground surface or in a trial pit, and works best on fine grained soils.

How It Works

Geotest can mobilise test equipment rapidly, and deliver results efficiently. The results of Mexe Cone Penetrmeter and Clegg Impact Soil Tests can be given instantly. All other tests are typically presented the next working day.

Accuracy is essential! – All Geotest test rigs are fully calibrated and well maintained.

Where there is uncertainty over what test is most suitable for your site, Geotest can mobilise a number of test rigs for additional confidence, and to prevent costly additional visits. Geotest have carried out testing on a range of sites including:

  • New road projects.
  • Proposed concrete bases for heavy plant.
  • Access tracks for solar PV projects.
  • Proposed crane pads.

Please call us to discuss your site requirements and the most suitable test for you.