Investigation of the Effect of Rock Characteristics on Crack Initiation and Crack Damage Stress Levels in Intact Rock Direct Shear Tests

Abstract

The increasing prevalence of deep mining and civil excavations has highlighted the significance of understanding and analyzing the failure of intact rock. Two critical stress levels in this context are the crack initiation stress and the crack damage stress, both of which are vital for understanding rock behavior during failure. Although numerous laboratory studies have been conducted on the compressive failure of intact rock, there are very few studies that analyze these two stress levels during the shear failure of intact rock. Previously, limited studies were conducted on granite rock. However, in this study, a synthetic rock sample with a much lower uniaxial compressive and tenslie strength than granite was created in the laboratory to examine the impact of other rock characteristics on the levels of crack initiation and crack damage stress in direct shear tests of intact rock. Both numerical modeling using discrete elements and physical modeling of direct shear tests on intact rock, along with acoustic emission analysis, were employed in this study. It was determined that for the rock sample of this study, the crack initiation and crack damage stress levels occurred at approximately 69% and 96% of the peak shear strength, respectively. This result supports previous investigations by showing that these stress levels occur in closer levels to the peak in direct shear tests rather than the uniaxial compressive tests. Moreover, it is showed that these shear stress levels is affected by rock characteristics like porosity, tensile strength, as same as the compressive stress conditions.