G5-1 G5 DIRECT SHEAR TEST GENERAL In a direct shear test a square prism of soil is laterally restrained and sheared along a predetermined horizontal plane while being subjected to a pressure applied normal to that plane. The shearing resistance offered by the soil, as one portion is made to slide on the other, is measured at regular intervals of displacement. Failure occurs when the shearing resistance reaches the maximum value which the soil can sustain. By carrying out set of tests on a set of (usually three sets) same soil sample under different normal pressures, the relationship between measured shear stress at failure and normal applied stress can be obtained. The shearbox apparatus is only suitable for carrying out drained tests for the determination of effective shear strength parameters. There is no control of drainage and the procedure cannot be used for undrained tests. OBJECTIVEThe purpose of the test is to determine the parameters of shear strength of soil (i.e. cohesion, c and angle of shearing resistance, ) by direct shear. APPARATUS 1. Specimen cutter 2. Shearbox apparatus (see Fig. G5-1 )3. Hanger weights 4. Weighing balance
