Influence of surface roughness and the degree of water saturation of rocks joints on the characteristics of microseismic emission signals under direct shear loading

An experimental study is carried out of the deformation process of the samples of siltstone and limestone with joints under direct shear with constant compressive load. The values of the degree of water saturation and the roughness coefficient of surfaces of joints varied. The aim of the work was to study the character of changes of the parameters of microseismic emission signals depending on the degree of water saturation and the roughness coefficient of the samples under direct shear loading. The first signals of microseismic emission appear at the stresses of 0.3–0.4 of the shear strength for the siltstone samples with high surface roughness values. The number of signals increases at the maximum load value and remains significant until the residual strength section. The highest values of the acceleration amplitude correspond to the break-downing of high roughness peaks. The direct shift occurs during monotonous sliding without sharply pronounced damage for limestone samples that are in a completely water-saturated state. It is confirmed by the absence of significant changes of the characteristics of microseismic emission signals.