A Study on Crack Initiation and Propagation in Rock with Pre-existing Flaw Under Uniaxial Compression

Abstract

A study for crack initiation and propagation in rock with a pre-existing flaw is carried under uniaxial compression. The aim is to understand the influence of crack initiation stress and peak stress for narrow flaws in rock by conducting laboratory experiments and subsequent numerical simulations. Specimens are prepared using Gypsum material with the incorporation of flaws at varying flaw angles from 15° to 75° having three different strengths. The results of the crack initiation and peak stresses for different flaw angles along with crack growth patterns are observed. Numerical simulations using ABAQUS adopting extended finite element and cohesive zone model is attempted to capture the crack initiation and propagation in rock specimens. For closed crack condition, the numerical model considers frictional behaviour across the flaw surface and model could capture the crack initiation and peak stresses along with propagated crack patterns irrespective of the material strengths. Both laboratory and numerical studies reveal that the crack initiation stress and peak stress gets initiated sooner for the flaw having 45° when compared to all other angles which are in contrast to open flaw conditions. Also at this angle, a stable curvilinear wing cracks are observed irrespective of the material strengths. In laboratory experiments, pre-dominant wing cracks are observed for a material having high strengths that influence the final pattern in specimens while in numerical analysis, all the specimens shows clear visible wing crack propagation and leads to failure of the material.