Studying seismic response of rock mass has been in the limelight during the recent decades. In the present study, Kelvin-Voigt model is adopted to model rock material viscosity where a nonlinear shear criterion is also employed to include the sliding mechanism across the joints. The both are then incorporated in the time-domain recursive method (TDRM) for calculating transmission and reflection coefficients. In order to assess the outcomes, a linearly elastic shear model is separately employed in the code so that the results could be comparatively analyzed. In the developed code, dynamic shear stress of the joints is monitored at each time step with respect to the dynamic shear strength in a way that sliding occurs whenever the slipping criterion is satisfied over a range of quality factors. Results clearly show that slipping exerts a significant negative effect on the shear transmission coefficients while inducing the opposite on the reflection coefficients. It is also observed that joint spacing plays a dual role on the results as emboldening the viscosity effects on one hand while improving the stability of the joints against sliding, on the other. This phenomenon which is induced by the dynamic normal stress of the joints, is shown to be reduced to zero in the case of normal incidence angle where the dynamic shear strength solely arises from the initial static shear strength. It is also shown that the maximum shear transmission coefficient could occur in a specific quality factor wherein the sliding starts to happen.

Studying seismic response of rock mass has been in the limelight during the recent decades. In the present study, Kelvin-Voigt model is adopted to model rock material viscosity where a nonlinear shear criterion is also employed to include the sliding mechanism across the joints. The both are then incorporated in the time-domain recursive method (TDRM) for calculating transmission and reflection coefficients. In order to assess the outcomes, a linearly elastic shear model is separately employed in the code so that the results could be comparatively analyzed. In the developed code, dynamic shear stress of the joints is monitored at each time step with respect to the dynamic shear strength in a way that sliding occurs whenever the slipping criterion is satisfied over a range of quality factors. Results clearly show that slipping exerts a significant negative effect on the shear transmission coefficients while inducing the opposite on the reflection coefficients. It is also observed that joint spacing plays a dual role on the results as emboldening the viscosity effects on one hand while improving the stability of the joints against sliding, on the other. This phenomenon which is induced by the dynamic normal stress of the joints, is shown to be reduced to zero in the case of normal incidence angle where the dynamic shear strength solely arises from the initial static shear strength. It is also shown that the maximum shear transmission coefficient could occur in a specific quality factor wherein the sliding starts to happen.