Numerical simulation of macro-meso mechanical behaviours of sandstone containing a single open fissure under uniaxial compression

Abstract

By employing the improved rigid block spring method, the failure process of a sandstone example containing a single open fissure under uniaxial compression is modelled. In this method, the intact rock is considered as an assemblage of rigid polygonal blocks. Macro mechanical behaviours are governed by mechanical properties of interfaces between two neighbouring blocks. In the local scale on interfaces, both tensile splitting failure and shearing sliding failure are considered. Micro properties are obtained by a calibration procedure against the stress–strain curve of intact rock under uniaxial compression in the lab. Influences of fissure inclination and length on the uniaxial compression strength (UCS) and failure modes are discussed. Comparisons between numerical simulations and laboratory tests are presented. The growth process of micro-cracks is studied and the mechanism of micro-crack propagation is studied through analysis on the displacement evolution. Some conclusions are drawn: numerical results generally agree well with those from lab tests; the UCS of fissured rock is lower than the intact one; the UCS first goes down then goes up as inclination increases, but decreases gradually as fissure length increases; the micro failure modes are governed mainly by tensile splitting failures.