Evaluation of the behaviour of jointed rocks due to small repetitive seismic loading

The effects of small cyclic loads and repetitive earthquakes on shear strength of rock joints have been investigated in this paper. More than 30 identical replicas have been tested using triaxial compression devices under different conditions of monotonic and cyclic loading. At the first stage few samples have been tested in monotonic loading modes under various confining pressures and rate of displacement. In the second series of tests, small cyclic loads were applied on the samples in different number of cycles, and stress amplitudes followed by monotonic loading. The variations of maximum and residual shear strengths for each test have been studied. The results show increase of shear strength with confining pressure and decrease of shear strength with increase of rate of loading, number of cycles, and stress amplitudes. Finally a mathematical model has been developed based on the test results.