Seismic response of adjacent filled parallel rock fractures with dissimilar properties

The purpose of this study is to analytically predict and to experimentally investigate the seismic response of adjacent filled parallel rock fractures with dissimilar properties (e.g., fracture thickness and stiffness). The time-domain recursive method is extended to predict that a P-wave propagates normally across the filled parallel fractures using the specific stiffness of each filled fracture and considering multiple wave reflections between the parallel fractures. The split Hopkinson rock bar technique is modified to simulate P-wave propagation normally across the sand-filled parallel fractures and to characterize the stress-closure relation of each sand-filled fracture. The P-wave transmission and the seismic response of the filled parallel fractures are an interactive process. The experimental results show the decreases of loading rate and dominant frequency when the P-wave propagates across each sand-filled fracture. The P-wave transmitted from the first sand-filled fracture strongly affects the seismic response of the second one. The P-wave attenuation in the filled parallel fractures is mainly due to the dynamic compaction of the filling sands. By comparison, the analytical method provides a satisfactory prediction to the experimental result. This study suggests considering the specific stiffness of each filled fracture to precisely predict the seismic response of filled parallel rock fractures. (C) 2013 Elsevier B.V. All rights reserved.