The vane shear test (VST) is performed to determine the shear strength of saturated cohesive soils using the Vane Test.
The test can be carried out in situ, on the wall or at the bottom of excavations, or in the laboratory on a suitably confined sample. The procedure involves inserting a four-bladed orthogonal vane into the soil; by rotating it at a prescribed speed, the value of the torque required to cause soil failure is measured using a calibrated torque wrench.
Subsequently, the rotation of the vane can be continued for several turns until the soil is completely remolded, in order to measure the residual shear strength of the soil after large deformations.