The present investigation is concerned with the interaction between the blast wave and a rock mass with a set of parallel joints by using a time-domain recursive method. According to the displacement field of a rock mass with a set of parallel joints, the interaction between four plane waves (two longitudinal-waves and two transverse-waves) and a joint is analyzed first. Considering the displacement discontinuity method and the time shifting function, the wave propagation equation based on the recursive method in time domain for obliquely longitudinal- (P-) or transverse- (S-) waves across a set of parallel joints is established. The joints are linearly elastic. The analytical solution by using the proposed method is compared with the existing results for some special cases, including incidence obliquely across a single joint and normal-ly across a set of parallel joints. By verification, it is found that the solutions by the new method match very well with the existing methods. Finally, a blast wave with different waveform propagating across a single or a set of parallel joints is then analyzed. The wave propagation equation derived in the present study can be straight forwardly extended for different incident waveforms to calculate the transmitted and reflected waves without mathematical methods such as the Fourier and inverse Fourier transforms.


The safety and stability of underground structures are often affected by blast induced waves which may come from an accidental explosion, the drill and blast excavation or weapon attacks. Since the underground structures are surrounded by jointed rock mass, the blast wave propagation in the rock mass is significantly influenced by the joints. The vastly existed joints in rock mass not only affect the mechanical properties of rock mass, but also their dynamic response (Goodman 1976). Therefore, studying the interaction between blast wave and joints has been drawing more and more attention (Berta 1994). The blast wave due to an explosion moves outward from the source rapidly and acts on the surrounding media by an effectively instantaneous rise in pressure followed by a decay of wave propagation in the rock mass (Henrych 1979). From a relative distance of the explosive centre, the blast wave is changed to an elastic wave and finally attenuated completely because of the energy dissipations both geometrically and mechanically. The interaction between a blast-induced stress wave and rock joints which relies on the impinging angle, type of the incident wave and the joint property mechanically dissipates the blast energy (Henrych 1979).

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