Ultrasonic P-wave propagation through water-filled rock joint : an experimental investigation

Abstract

The presence of fluids in rock discontinuities may dramatically affect wave behaviours of rock masses, e.g., wave velocity, wave transmission and attenuation. In this study, extensive laboratory tests of ultrasonic P-wave propagation across water-filled rock joints were conducted to investigate the effects of joint thickness and water content on compressional wave propagation in the ultrasonic frequency range were investigated. P-waves with two different central frequencies of 0.1 MHz and 1.0 MHz were applied to study ultrasonic wave characteristics of rock with a single water-filled joint under different joint-thickness-wavelength-ratio conditions. The experimental data were collected and used for the analysis of wave velocity, transmission coefficient and attenuation quality factor of rock samples with water-filled rock joints. The results showed that the increase of joint thickness could cause more wave attenuation while the increase of water content could lead to less wave attenuation. In addition, the wave velocity is higher, yet wave transmission is weaker for higher-frequency waves (1 MHz). The results and findings were elaborated and explained through the fundamental physics of acoustics in fluids and rocks. The present paper is of great significance to characterize the wave responses of rock discontinuities filled with fluids.