Wave transmission across linearly jointed complex rock masses

Abstract

This paper presents an investigation of wave transmission in complex rock masses; the rocks have different wave impedances on either side of a joint. The conventional displacement discontinuity method was modified for complex rock mass wave propagation by introducing four sets of characteristic lines. Two cases, “soft-to-hard” and “hard-to-soft” rock masses, were used to demonstrate wave propagation through the complex rock masses. The results show that the wave impedance ratio plays an important role in the wave propagation through the complex rock masses. For the case of “soft-to-hard” rock masses, the particle velocity transmission ratios are always smaller than 1.0, while the stress transmission ratios may be larger than 1.0 when the wave impedance ratio and the frequency of the incident wave are sufficiently small. On the other hand, for the case of “hard-to-soft” rock masses, the stress transmission ratios are always smaller than 1.0, while the particle velocity transmission ratios may be larger than 1.0 when the wave impedance ratios are sufficiently large and the frequencies of the incident wave are sufficiently small. The phenomenon indicates that wave propagation in complex rock masses is not always attenuated but may actually be enhanced in some cases.