A numerical analysis of the effect of rock bridges on wave propagation

Rock masses consist of intact rock and discontinuities such as faults, joints and bedding planes. The presence of such discontinuities in rock masse dominates the response of jointed rock masses to static and dynamic loading. These structural weak planes seriously hinder and affect the propagation of stress waves in rock mass. The joints parameters such as persistence, orientation, distribution patterns, spacing and filling material have a significant effect on the response of rock masses against wave propagation. In most studies of blastinduced wave propagation in jointed rock mass, it is assumed that the joints are continuous. In many situations the rock mass consists of non-continuous joints and rock bridges. Rock bridges and discontinuous joints have a different effect on wave and fracture propagation in the blasting process. With regard to the complexities associated with rock blasting, in particular in jointed media, numerical tools are viable alternatives for rock blasting analysis. In this study the DEM method was employed to investigate the effects of rock bridges on blast-induced wave propagation. A plain strain 2D scenario was assumed and a single blasthole explosion was simulated. The analysis results show that the stress concentration at the rock bridge location leads to excessive fracturing. This effect is more visible at the free face where the stress wave reflection occurs.