Vane Test Procedure – Shear Strength of Soils

The Vane test is a field shear test for clays in which a vane consisting of two or four blades fixed at right angles, is attached to the end of rod and pushed into the soil at the bottom of a borehole. The torque required to cause rotation or shear the soil is measured. This torque is approximately equal to the moment developed by the shear strength of the clay acting over the surface of the cylinder with a radius and height equal to that of the vanes. The vane test has the advantage over the unconfined compression test in that the shear strength of a soft and sensitive clay at considerable depths (say up to about 30 m) can be determined insitu without obtaining undisturbed samples. This test is still in the process of development.