ASTM D6951/D6951M-18 PDF Download

The ASTM D6951/D6951M-18 standard outlines a testing procedure for assessing the strength of undisturbed soil and compacted materials in situ. This test method involves using an 8-kg (17.6-lb) dynamic cone penetrometer (DCP) to measure the penetration rate through the material of interest. The penetration rate can be used to estimate the in situ California Bearing Ratio (CBR), as well as other material characteristics such as strata thickness and shear strength.

The standard highlights that there are other test methods available for DCPs with different hammer weights and cone tip sizes, each with unique correlations specific to the instrument. The 8-kg DCP is typically used in horizontal construction applications, such as pavements and floor slabs.

The DCP is capable of assessing material properties down to a depth of 1000 mm (39 in.) below the surface, with the option to increase penetration depth using drive rod extensions. However, care needs to be taken when using correlations to estimate other parameters as the device's mass and inertia will change, and skin friction along drive rod extensions may occur.

The 8-kg DCP is suitable for estimating the strength characteristics of fine- and coarse-grained soils, granular construction materials, and weak stabilized or modified materials. However, it is not appropriate for highly stabilized or cemented materials or granular materials with a large percentage of aggregates greater than 50 mm (2 in.).

If the underlying material is covered by a bound or highly stabilized layer, an access hole needs to be drilled or cored to assess the strength characteristics of the in situ material. It is worth noting that the field DCP measurement results in a field or in situ CBR which may not correlate with the laboratory or soaked CBR of the same material. The test is therefore intended to evaluate the in situ strength of the material under existing field conditions.