Laboratory and Field Testing

Dynamic cone penetrometer

The dynamic cone penetration (DCP) test provides a measure of a materials in-situ resistance to penetration. The test is used to determine the structural properties of sub-grade materials beneath road pavements.

The DCP test equipment is robust, easy to use, portable and suitable for use in locations where access may be restricted. The test is performed by driving a metal cone into the ground by repeated striking with an 8kg weight dropped from a distance of 575mm.

The penetration of the cone is measured after each blow and is recorded to provide a continuous measurement of shearing resistance up to 1m below the ground surface. The test is terminated if the desired depth is reached or the rod does not penetrate. Correlations have been established between the DCP and in-situ CBR measurement enabling the results to be interpreted and compared with specifications for highway or pavement design.

For highway or pavement design purposes the DCP test is used to estimate the sub-grade strength. If the DCP cone penetrates quickly into the soil, it indicates that the material has poor strength or insufficient compaction. Either thicker pavement layers might be needed or better compaction. If a large number of blows is required to cause the cone to penetrate a short distance the sub-grade is well compacted.