Shearing Behaviour of Jointed Rocks Under Monotonic and Cyclic Loading with Varying Gouge Materials

Abstract

Rock is not homogeneous and isotropic due to the presence of discontinuities and weak planes within its body. This brings in terms of ‘rock material’ and ‘rock mass’ for practical applications. A rock mass is an assemblage of intact rock pieces separated by discontinuities presented in different scales such as micro-fractures, rock joints, stratification, faults. For design in civil and mining engineering geo-structures, it is often necessary to investigate the behaviour and role of discontinuities on rock mass performance. In many cases, failure is governed by the shear behaviour of discontinuities in excavations. In this context, evaluation of the effects of small repetitive earthquakes on the shear strength parameters of rock joints especially in tunnels and dam foundations is also important. The main scope of work is to study and investigate shearing behaviour of jointed rocks infilled with gouge materials under monotonic and cyclic loading vis-a-vis the theoretical background to shearing behaviour under loading conditions to compare the shear strength values for a variety of jointed rocks. In case of cyclic loading, under the initial loading cycles, the rate of increase of displacement is slow corresponding to the rate of increase of shear stress. In later load cycles, the rate of displacement is rapid with a corresponding increase in shear stress until the peak shear stress value is reached. Under cyclic loading condition, post peak behaviour sometimes exhibits a tendency to drop suddenly and assumes a constant value called residual shear stress.