Mechanical behavior and acoustic emission characteristics of intact granite undergoing direct shear

Abstract

Shear behaviors of core samples from a deep geothermal exploration well was investigated using direct shear tests. The fracturing process inside the intact rock samples during shear was monitored using acoustic emission (AE) technique. The results show that three shear stages including compaction, quasi-elastic and failure phases can be easily divided based on the shear stress-shear displacement or the cumulative AE parameters-shear displacement curves. Three characteristic stresses in terms of crack initiation stress, crack damage stress and peak strength are defined for intact rock samples undergoing shear. The crack initiation stress is about 0.80 times of the peak strength, and the crack damage stress is about 0.88 times of the peak strength. In addition, the different shear behaviors and AE characteristics between intact rocks and rock fractures are compared. AE events are scattered in the pre-peak stage but are localized around the fracture surface in the post-peak stage, while AE events are located along the shear zone in intact rock samples.