Direct Shear Test

The Direct Shear test is carried out with an apparatus consisting of a square or circular box divided into two halves. The specimen, contained in the box, is subjected to a constant normal load while an increasing horizontal force is applied to one of the sections of the shear box. This force causes a shear failure along the juncture between the box sections. The shear force and the normal load are measured directly. The rate of strain is adjusted by the speed of the horizontal force applied. The loading unit has V-Strips on which the shear box housing rests. The pre-calibrated load yoke helps counter balance the loading system. The load yoke with direct and through level system for applying normal load upto 8 Kg/cm2 capacity. Fixtures for proving ring, brackets for holding consolidation and strain dial gauges are pro-vided. The lead screw connected to the shear box housing helps application of shear stress. Shear strength of the soil is its maximum resistance to shearing stress. The shear strength is expressed as - s = c’ + σ’ tan ø’

Where c’ = effective cohesion σ’ = effective stress Ø’ = effective angle