Effects of filling fluid type and composition and joint orientation on acoustic wave propagation across individual fluid-filled rock joints

Abstract

Wave propagation and attenuation in subsurface rock masses could be highly affected by rock joints filled with fluids. However, the understanding of acoustic behaviours across fluid-filled rock joints is still at its infancy. To determine the effects of the type and composition of filling fluids as well as joint orientation on compressional wave propagation and attenuation across individual fluid-filled rock joints, extensive laboratory acoustic tests were conducted in this paper. Results showed that the existence of water in fluid-filled rock joints results in higher wave velocity, more wave transmission and less wave attenuation compared to light oils. In most circumstances, increasing liquid content in a single-liquid filled joint enhances wave velocity and wave transmission. For dual-liquid filled joints, both wave velocity and wave transmission increase with increasing water content. Joint orientation significantly affects wave characteristics of rock joints partially filled with liquids while it has slight influences on wave attributes of rock joints fully filled with liquids. In addition, wave velocity and attenuation across fluid-filled rock joints increases with increasing central frequency of incident compressional waves.