5.1 This test method is used to assess in situ strength of undisturbed soil and compacted materials (or both). The penetration rate of the 8-kg [17.6-lb] DCP can be used to estimate in situ CBR (California Bearing Ratio), to identify strata thickness, shear strength of strata, and other material characteristics.

5.1.1 Other test methods exist for DCPs with different hammer weights and cone tip sizes, which have correlations that are unique to the instrument, such as Test Method D7380.

5.2 The 8-kg [17.6-lb] DCP is held vertically, and therefore is typically used in horizontal construction applications, such as pavements and floor slabs.

5.3 This instrument is typically used to assess material properties down to a depth of 1000 mm [39 in.] below the surface. The penetration depth can be increased using drive rod extensions. However, if drive rod extensions are used, care should be taken when using correlations to estimate other parameters, since these correlations are only appropriate for specific DCP configurations. The mass and inertia of the device will change and skin friction along drive rod extensions will occur.

5.4 The 8-kg [17.6-lb] DCP can be used to estimate the strength characteristics of fine- and coarse-grained soils, granular construction materials, and weak stabilized or modified materials. The 8-kg [17.6-lb] DCP cannot be used in highly stabilized or cemented materials or for granular materials containing a large percentage of aggregates greater than 50 mm [2 in.].

5.5 The 8-kg [17.6-lb] DCP can be used to estimate the strength of in situ materials underlying a bound or highly stabilized layer by first drilling or coring an access hole.

Note 1: The DCP may be used to assess the density of a fairly uniform material by relating density to penetration rate on the same material. In this way, undercompacted or "soft" spots can be identified, even though the DCP does not measure density directly.3

5.6 A field DCP measurement results in a field or in situ CBR and will not normally correlate with the laboratory or soaked CBR of the same material. The test is thus intended to evaluate the in situ strength of a material under existing field conditions.