What type of soils cannot be tested with the Cone Penetration Test?

The Cone Penetration Test (CPT) is primarily used to assess the properties of soil and to determine the bearing capacity of the ground. It involves pushing a cone into the ground at a constant rate and measuring the resistance felt by the cone.

Gravely or very stiff soils pose challenges for the CPT primarily due to their composition and density. In gravely soils, the presence of larger particles can lead to difficulties in penetrating the ground, while very stiff soils may resist penetration effectively, resulting in unreliable or incomplete data. The test relies on the ability to push the cone into the ground smoothly, and when the soil is too stiff or contains larger particles like gravel, this action becomes impeded.

On the other hand, loose soils, silty soils, and clay soils are generally appropriate for testing. Loose soils can be penetrated easily, providing useful data about soil stratigraphy and strength. Silty soils, while they can have some cohesive properties, still allow for the proper penetration of the cone. Clay soils can also be tested, as their plasticity and cohesion allow for reliable measurements, although care must be taken to account for cohesion effects in analysis.

Understanding the limitations of the CPT in various soil conditions is crucial for making accurate geotechn