Pocket penetrometer

The pocket penetrometer is used to determine the unconfined compressive strength (UCS) of the (undisturbed) soil, which gives a good indication of the maximum axial compressive stress the material can withstand under unconfined conditions. Based on the results of the test, it is possible to calculate the undrained shear strength (Cu).

The device is pressed steadily into the soil, creating a backpressure from the soil onto the device, which causes a spring inside the device to compress and, subsequently, resistance. The device has calibrated scale on the side, allowing for a direct reading of the penetration resistance. The unconfined compressive strength can finally be calculated and expressed in kN/m2 or kPa.