Shear velocity and normal stress level effects on shear stiffness of rock joints

Shear stiffness is an important parameter of rock joints. This parameter along with normal stiffness is the basic input data of numerical modeling of jointed rock masses. There are several factors that influenced shear stiffness. In this paper, the effects of shearing velocity, normal stress levels and the material of shearing blocks on shear stiffness are investigated. Artificial joint with planar surfaces were prepared with plaster (soft rock-like joints) and concrete (hard rock-like joints) and shear tests were performed on these samples under various normal stress levels and shearing velocities in the range of 0. 3-30 mm/min. Results indicated that with increasing of shear velocity shear stiffness decreased. On the other hand, when normal stress levels increased, shear stiffness increased linearly. This relation was named «shear stiffness linear envelope». It is remarkable that these results are correct for both artificial joints of different materials.