The TRL DCP (Dynamic Cone Penetrometer) is an instrument designed for the rapid insitu measurement of the structural properties of existing road pavments constructed with unboun materials. Continuous measurements can be made down to a depth of approximately 850mm or when extension shafts are used to a recommended maximum depth of 2m. Where pavement layers have different strengths the boundaries can be identified and the thickness of the layers determined. Correlation's have been established in earlier work (Van Vuuren 1969, Kleyn and Van Heerden 1983, Smith and Pratt 1983) between measurements with the DCP and CBR (California Bearing Ratio) so that resuls can be interpreted and compared with CBR specifications for pavement design. A typical test takes only a few minutes and therefore the instrument provides a very efficient method of obtaining information that would normally require the digging of test-pits.

Penemeters are used to establish the thickness of different stratifications when investigating the suitability of a site for bridge, road and other construction works. In general if the ground is not too compact, penetration tests with the lightweight penetrometer can be carried out to depths of about 6m.