Experimental and Numerical Study on Mixed Crack Propagation Characteristics in Rock-Like Material Under Uniaxial Loading

Abstract

The cracks of rock mass were in complicated geometric distribution, whose propagation characteristics and stress distribution change with the geometric distribution accordingly. In this research, propagation tests on mixed crack (horizontal edge cracks and inclined cracks) were conducted to analyze the propagation characteristics and stress distribution by lab tests and numerical modelling. The failure mode of specimens in Group 1 and Group 2 was the mixed crack (shear crack and tensile crack) and the coalescence of the pre-existing cracks propagation, respectively. The crack initiating from edge crack was the mixed crack–shear crack and tensile crack, and the crack initiating from inclined crack was the wing crack–tensile crack. The peak of energy index appeared in the crack initiation, coalescence and specimen failure. The energy release of an inclined crack was less than that of an edge crack. The existence of pre-existing inclined crack resulted in the strength decrease of specimens. Stress concentration produced in the tips of the pre-existing cracks, and the concentration degree of edge cracks was much bigger than that of inclined cracks. The mechanism of buried structure water inrush was illustrated in this study. The working faces and buried structure could be simplified as the horizontal edge crack and inclined crack. The buried structure (inclined cracks) propagated and connected with the mining damage zone (horizontal edge cracks) and confined aquifer, so that water inrush paths were formed in the buried structure (similar to macroscopic cracks formed by the pre-existing crack propagation). This research provides a reference for the study on the water inrush in the buried structure.