Experimental and DEM study on failure behavior and stress distribution of flawed sandstone specimens under uniaxial compression

Abstract

Rock materials contain various scales of pre-existing flaws that greatly influence the stability of rock engineering. The study of strength and failure behavior of pre-flawed rock enhances the understanding the fracture mechanism of rock. In the present study, uniaxial compression tests were carried out on sandstone specimens containing three pre-existing flaws at various inclination angles. The experiment results indicated that the stress–strain curves, mechanical paprameters, acoustic emission and failure pattern of pre-flawed specimen were affected by the pre-existing flaws. To verify the test results, a PFC modelling was conducted on pre-flawed specimen using a set of calibrated parameters. The stress–strain curve, mechanical paprameters and failure mode of specimen containing three flaws were reproduced in the numerical simulation. Three types of crack, i.e., tensile crack, shear crack and mixed tensile-shear crack, were identified based on the laboratory micro observations and numerical displacement field. As the flaw angle increased from 0° to 90°, the tensile stress concentration gradually deteriorated and transferred from the middle to the tip of pre-existing flaw. The evolution of internal stress surrounding the pre-existing flaw during the crack initiation, propagation and coalescence process was further discussed. This experimental and numerical study aims to investigate the crack characteristic and internal stress evolution in fractured rock.