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Due to active actions of groundwater and geothermal, the stability of underground engineering is important during geological structure active area. The damage mechanical theory and statistical mesoscopic strength theory based on Weibull distribution are widely used to discuss constitutive behaviors of rocks. In these theories, a statistical method is used to capture mesoscopic properties of rocks in order to generate a realistic behavior at a macroscopic scale. Based on the above theories, this paper aims at establishing a constitutive relation of brittle rocks under thermal-mechanical coupling conditions. First, a statistical damage constitutive model was established by considering the thermal effects and crack initiation strength. Subsequently, the parameters of the model were determined and expressed according to the characteristics of stress-strain curve. Third, the model was verified by conventional triaxial experiments under thermal-mechanical actions, and the experimental data and theoretical results were compared and analyzed in the case study. Finally, the physical meaning of the parameters and their effects on the model performance were discussed.

According to the test results of the physical and mechanical properties of similar materials in various quality mixture, a type of material with obvious tendency of rockburst was selected to produce a large-size model to simulate rockburst phenomena in tunnels. The prototype model comes from a typical section of diversion tunnels in Jinping Hydropower Station in China. The simulation of excavating tunnels is carried out by opening a hole in the model after loading. The modeling results indicated that under the condition of normal stresses in the model boundaries the arch top, spandrel and side walls of the tunnel produced an obvious jump reaction of stress and strain and the acoustic emission counts of the surrounding rock also increased rapidly in a different time period after the "tunnel" excavation, showing the clear features of rockburst. The spalling, buckling and breaking occurred in the surrounding rock of model in conditions of over loading. It is concluded that the modeling tunnel segment in Jinping Hydropower Station is expected to form the tensile rockburst with the pattern of spalling, buckling and breaking.