Cone Penetration Tests

A cone penetration test (CPT) is one of several methods used to carry out ground investigation. In a cone penetration test, a cone-shaped probe is driven into the ground at a constant rate via a system of rods. The cone penetration test measures the tip pressure and wall friction, which are expressed in megapascals (MPa).

What is the purpose of cone penetration tests?

Cone penetration tests are used to assess the bearing capacity for pile foundations, but also, more generally, to obtain a quick overview of the soil structure.

How are pressure probing tests carried out?

On the mainland, the tests are usually carried out using specially converted lorries, which also provide the counterweight for the hydraulic injection. Due to the equipment required, cone penetration tests are usually carried out by specialist geotechnical firms.

What information is obtained from a cone penetration test?

The force measurement is carried out electrically. Based on the point pressure, direct conclusions can be drawn regarding the density of an unconsolidated soil. The ratio of skin friction to point pressure provides information about the soil type (cohesive or non-cohesive soils). Other soil parameters that can be derived from the cone penetration test include, for example, the internal friction angle for unconsolidated soils, the consolidation coefficient and the undrained shear strength for cohesive soils.

When are pressure penetrations not suitable?

Cone penetration tests are not suitable for very stiff soil types and soil types with high density, gravel layers and stones in the soil, which can not only damage the probe tip but also lead to unacceptable displacements of the rod assembly.