Time-dependent propagation and interaction behavior of adjacent cracks in rock-like material under hydro-mechanical coupling

Abstract

Under the long-term coupling effects of seepage pressure and geo-stress, the interaction and propagation of cracks in rock mass show typical time-dependent characteristics, and directly control the failure mode of rock mass. The laboratory tests under long-term hydro-mechanical coupling were carried out based on the cement mortar specimen containing adjacent pre-existing cracks, and the micro crack evolution in the specimen was analyzed by using low-frequency nuclear magnetic resonance technology, the corresponding numerical simulation was carried out to study the propagation and interaction behavior of adjacent cracks and the time-dependent mechanism of creep failure of rocks. The results show that: The creep failure of rock mass with adjacent cracks presents a tension-shear composite mode; The macro fracture is formed by the propagation of one crack and does not connect with the adjacent crack; Due to the interaction effect between cracks, a large number of micro cracks are formed in the specimen, and the propagation of adjacent pre-existing cracks is non-uniform, and the propagation of upper and lower wing cracks of the dominant crack is asymmetric; In the crack initiation stage, the crack propagation is controlled by the shear fracture mode, and the interaction shows the inhibition of adjacent cracks; After propagating to a certain extent, the dominant crack propagation is controlled by the tensile fracture mode, and its propagation rate increases, which accelerates the failure of rock mass.