This document specifies laboratory test methods to establish the effective shear strength parameter for soils within the scope of the geotechnical investigations according to prEN 1997-1 and -2.
The test method consists of placing the test specimen in the direct shear device, applying a pre-determined normal stress, providing for draining (and wetting if required) of the test specimen, or both, consolidating the specimen under normal stress, unlocking the frames that hold the specimen, and displacing one frame horizontally with respect to the other at a constant rate of shear-deformation and measuring the shearing force, and horizontal displacements as the specimen is sheared. Shearing is applied slowly enough to allow excess pore pressures to dissipate by drainage so that effective stresses are equal to total stresses.
Direct shear tests are used in earthworks and foundation engineering for the determination of the effective shear strength of soils.