Direct Simple Shear (DSS)

The Direct Simple Shear (DSS) test is used to the possibility to determine the shear strength of a soil sample by applying a force in opposite directions; commonly used for peat-soils as well as studies on the strength of dykes. In contrast to the Direct Shear test, during the DSS test the sample is not enclosed on all side and, therefore, without a predefined shear plane. Using numerous metal rings the sample is consolidated under in-situ effective stress (normal consolidation (NC)) or higher (over consolidation (OC)) before the shearing phase is initiated. The sample is allowed to uniformly deform without forming a single shearing surface. This means that the sample should shear at its weakest point, and is not forced to shear in the centre of the sample. Furthermore during the DSS test it is possible to maintain either a constant vertical load during shearing, or a constant volume of the sample constant by upholding its height. The latter determines the undrained shear strength, whilst the former determines the drained shear strengths

Geolab Wiertsema has six Direct Simple Shear devices set up in a conditioned part of the  laboratory in Tolbert, The Netherlands.