Shear waves are considered as one of the damaging waves for any structure built in the rocks during earthquakes, mining, blasting etc. This paper describes the numerical simulation of a test facility that generates shear waves in rocks. The test facility comprises of a dynamic impact mechanism, friction bar, incident, and transmitted plates. When the friction bar is given dynamic impact, shear wave gets generated in the perpendicular direction in the incident plate due to friction present in the interface between friction bar and incident plate. Seismic impedance of the media plays an important role during wave propagation across the interface. The effect of change in material density across the frictional joints was monitored during laboratory testing. These tests were numerically simulated using a distinct element code. Validation of these numerical simulations have been done by monitoring the vibration amplitudes developed at various locations of the plates in the laboratory.
Naturally, rock mass has multiple discontinuities, such as faults, joints, and fissures. Jaramillo (2017) addressed the need for stability analyses of subsurface structures built in rocks subjected to dynamic loads. Several analytical studies, including Pyrak-Nolte and Cook (1987) applied Displacement Discontinuity Method (DDM) to analyse the wave propagation across discontinuous media. The joints present in the rocks were proven to have a considerable impact on wave propagation. For the experimental researches on wave propagation across rock joints, wave velocities and wave attenuation are measured at various strain rates. The split Hopkinson pressure bar (SHPB) designed by Kolsky (1963) is one of the most widely used loading systems at high strain rate (101-104 sec−1). Several researchers (Li and Ma 2009, Wu et al. 2013) employed the SHPB test to evaluate the dynamic response of rocks at high strains during compression wave propagation. Liu et al. (2017) designed the split shear plate (SSP) facility using the direct shear model (Wu and Zhao 2014) and SHPB theory for analyzing shear wave propagation. The study on shear wave propagation across rocks of various seismic impedances using laboratory experiments and numerical simulations is presented in this paper. Seismic impedance (defined as product of density and velocity of wave propagation in that medium) is considered as an important parameter in the propagation of waves across rock joints.
