Undrained shear strength (Labvane)

The laboratory vane (Labvane) test is used to determine the undrained shear strength of both undisturbed and remoulded samples of fine-grained (cohesive) soils, as a function of the torque needed for shearing. The undrained shear strength is expressed in kN/m².

During this test a cruciform vane is pressed into the undisturbed sample and gradually rotated until the soil has sheared. The torque needed to reach the point of shearing is recorded and used to calculate the undrained shear strength of the undisturbed sample (peak value).
In case the residual strength is requested as well, the vane is rotated rapidly through two full rotations to remould the soil. Subsequently the initial procedure is repeated to determine the residual value. Soil sensitivity can be derived from the quotient of both measurements.