Shear behavior of rock under different normal stiffness

The shear behavior of rock joints greatly influence by the presence of asperity and the normal stiffness of the surrounding rock mass. Correct evaluation of the shear strength of rock joints plays an important role in the design of deep underground openings, stability analysis of rock slopes, socketed piles in rock and anchored rock slopes. To study influence of normal stiffness of the surrounding rock mass on the shear behavior of non planar rock joints, tests were performed on an automated servo controlled large scale direct shear testing machine, which has been designed and developed at IIT Delhi (Rao et al. 2009a). Tests can be conducted on equipment to study the effect of joint roughness, scale effects, stiffness of the surrounding rock, shear rate, condition of the joint i.e. unfilled joint/in filled joint, infill type and infill thickness affecting the shear behaviour of rock joint. Influence of some of these parameters on shear strength of jointed rock has been studied by different researchers such as Patton (1966), Ladanyi & Archambault (1970), Barton (1973) and Indrartna & Haque (1998, 1999). Extensive tests were conducted on non planar rock joints of asperity angle of 15 degrees-15 degrees of 5mm thickness at different normal stiffness and presented the test results.