Laboratory Assessment for Frictional and Joint Deformation Properties of Rock

This paper describes about laboratory assessment of frictional and joint stiffness parameters of slate and quartzite rocks obtained from Himalayan region, under constant normal load (CNL) condition. The investigation was carried out using laboratory direct shear test apparatus both on tight and open jointed samples. The estimated values of cohesion and friction angles at peak and residual shear stress were compared for both jointed rocks. It is observed that the frictional parameters of open jointed quartzite rocks have resulted in lower values than tight jointed slate rocks. An attempt was also made to estimate normal stiffness and shear stiffness of these jointed rocks. Irrespective of rock type and nature of joint, nonlinear behaviour is witnessed through stiffness data invariably. In comparison, the tight jointed slate rocks gave much higher values of stiffnesses than the open jointed quartzite rocks. As applied normal stress increases, the slope of the shear stress versus shear displacement of open jointed rocks changes from smooth to rough.