In-situ deformability and strength characteristics of Himalayan granites

Deformability and shear strength of rock mass are the two most important characteristics that are frequently used in the analysis and design of structures in or on rock. Apart from the inherent characteristics of geological mass, deformability and shear strength parameters of rock mass depend upon several other field conditions as well. It is necessary to conduct in-situ deformability and in-situ shear tests as it is impractical to simulate field conditions in laboratory. Deformability characteristics (deformation modulus and modulus of elasticity) are generally obtained by conducting the plate load tests and recording the vertical load-deformation data inside a drift or in a trench as per the site conditions. Determination of the shear strength parameters (cohesion and friction angle) involves the shearing of the block under constant vertical stress at the concrete-rock and rock-rock interface. The present study is based upon in-situ plate load tests and shear tests which were conducted in two dam-axis drifts of Kirthai hydroelectric project Stage-II, Jammu & Kashmir. A detailed discussion on in-situ deformability characteristics and shear strength parameters of granite rock mass (Himalayan region) has been carried out.