The Direct Simple Shear test is a laboratory testing method used to directly determine the shear modulus of soil.
The principle of the test is inducing direct shear in a cylindrical soil sample (usually peat). The cylindrical soil sample is confined by a flexible wire-reinforced rubber membrane usually inside metal rings. The sample is placed between the base pedestal and the top cap. Vertical stress is applied to the sample from the top cap. The sample is sheared by moving the rings from side to side.
The DSS-test is especially interesting for the research of weak types of soil (clay and peat) in areas where the risk of shearing has to be determined. At the moment the test is often used for the research of the strength of dykes.