ABSTRACT
Failure behaviour of rock mass is dependent upon the rock fracturing process and that in-turn dependent upon the crack initiation and propagation. The analysis of crack growth on a rock with pre-existing flaws is mostly carried out in open flaw configurations whereas limited study can be found for narrow flaw configurations. Unlike open flaw, narrow flaws are initially open and subsequently gets closed during loading. It also experiences friction which needed to be accounted for. Very few studies are available, to understand the effect of friction between the flaw surfaces. Additionally, the lateral confinement due to the biaxial confinement state would influence the crack initiation and their subsequent growth. In the present study, an experimental investigation is conducted to understand the crack growth behaviour of narrow flaws under uniaxial and biaxial stress environments. The tests were conducted using gypsum with a single flaw at varying orientation. The change in the behaviour of crack growth and stresses with respect to initiation and peak stress level was studied for different flaw angles. Subsequently, the numerical analysis was performed using the Extended Finite Element Method (XFEM) in conjunction with the Cohesive Zone Model (CZM). The model systematically validated with the laboratory experiments. The crack pattern was found to be influenced by various factors namely flaw angle, frictional coefficient between the flaw surface, the confinement stress level.
