On using the thin fluid-layer approach at ultrasonic frequencies for characterising grout propagation in an artificial fracture

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

“…Specifically, the difference between wave impedances of rock matrix and water is the smallest, thus more wave energy transmits across the rock-water interface of the joint [18]. Apart from that, it could also be attributed to the contrast in liquid viscosity [17,22,48]. Viscosity of water is smallest among these three liquids, and viscosity of M68 is much greater than that of BL10, as shown in Similar variations of spectral contents caused by the increasing liquid content for horizontal joints with filling liquid content higher than 50% were also observed from Figs.…”

“…It means that water-filled rock joints attenuate less wave energy than BL10and M68-filled joints, and more wave attenuation occurs in M68-filled joints rather than BL10filled joints. The observed small discrepancy in wave attenuation caused by different filling liquids could be attributed to the significant difference in viscosities of these liquids [17,22,48]. attenuate more wave energy compared to BL10.…”

“…Minato and Ghose conducted ultrasonic tests on single dry and water-filled fractures and stated that the calculated fracture compliance ratio from the P-P and P-S amplitude-versus-offset (AVO) inversion could be applied to accurately estimate the existence of fluid in the fracture [21]. Additionally, Place et al carried out ultrasonic tests on an artificial fracture filled with various fluids, where the filling fluid was almost at rest in the fracture or moving at a controlled flow rate through the fracture [22]. They found that the types of fluids could highly affect reflected wave spectra and energy, while the internal fluid flow has negligible influences on wave reflection.…”

Water Inrush from Pregrouting Fractures Induced by Mining Activities and Its Engineering Control Method Optimization

“…Generally, there are mainly three key scientific issues concerning underground water threat during coal production, including the mechanism of water inrush [3][4][5], the prevention approaches of water inrush [6,7], and the evaluation of grouting effect [8]. Specifically, there are many factors affecting water inrush such as formation pressure, productivity, geologic structures, and the water pressure in the confined aquifer, though the declining of constraints due to mining is the major cause of the water-conducting failure of the floor rock strata in the coal seams [3].…”