Microcracking Mechanism Analysis of Rock Failure in Diametral Compression Tests

A moment tensor analysis of acoustic emission was applied to quantitatively study the microcracking mechanism and damage evolution process in cylindrical specimens of granite and sandstone under diametral compression. It was found that the localized damage zone tended to originate and propagate from the vicinity of the loading ends. During the damage accumulation process, the tensile cracks played a dominant role in number, but the acoustic emission (AE) energy release of microcracks of different types presented an inconsistent trend for the two types of rock. Scanning electron microscope (SEM) observations on the fractured surfaces were conducted, which indicated that during the rock failure process there coexisted microcracks of three typestensile, shear, and mixed-modedue to the heterogeneity of the mechanical properties of the rock. The microscopic observations using a polarized light microscope technique revealed that the mineralogical composition and microstructure of rock had a significant effect on its microcracking mechanism.