Abstract:To study the failure characteristics of surrounding rock near an excavated tunnel under different three-dimensional stress conditions, a TRW3000 rock true triaxial electro-hydraulic servo mutagenesis testing system was used to conduct triaxial loading experiments on granite specimens with a circular hole. A high-definition micro-camera system was used to record the failure process near the circular hole. The results show that spalling failure occurs near the holed specimen under low-stress conditions, and rockburst appears around the holed specimen under high-stress conditions. Increasing the horizontal stress can prevent the occurrence of rockburst. The evolution of strain energy density (SED) in the surrounding rock of the holed specimen under different stress conditions was simulated. The findings show that the distribution of SED around the circular hole decreases with an increase in horizontal stress. The SED distributions around the circular hole are basically consistent with the damage distributions in the experiments, namely, butterfly-shaped, ear-shaped, and ring-shaped.

Key words: deep hard rock tunnel; true triaxial experiment; horizontal stress difference; failure characteristics; energy distribution