Specialists in Soil and Water Sampling, Testing and Monitoring

The UK Transport Research Laboratory (TRL) Dynamic Cone Penetrometer (DCP) is an instrument designed for rapid insitu measurement of the structural properties of existing road pavements constructed with unbound materials. Continuous measurements can be made down to a depth of approximately 900mm. Where pavement layers have different strengths, the boundaries can be identified and the thickness of the layer identified.

Correlations between the results of the DCP test and California Bearing Ratio (CBR) have been identified (Van Vuuren 1969, Kleyn and Van Heerden 1983, Smith and Pratt 1983). The correlations allow the rapid assessment of insitu CBR values.

Using the above correlations, the results of the DCP test results can be presented in the form of a continuous CBR vs Depth profile. The test is inexpensive and takes a few minutes to complete making it an ideal tool for the Site Investigation stage of any development.

Agreement is generally good over most of the range, but differences are apparent with low CBR values in fine grained soils.  In such circumstances CBR values derived from the TRL DCP should be treated cautiously.

Sample CBR results using the TRL DCP test