# Study on Damage Behavior and Its Energy Distribution of Deep Granite at High-Temperature Conditions
## 4 Discussion  
1. In the research of rock mass engineering, the primary task is to obtain the distribution characteristics of anisotropic crack in rock mass by using ultrasonic borehole television technology. Using borehole TV, the crack dip angle in the scanning area is segmented statistics, so as to obtain the distribution law of crack occurrence. Secondly, by analyzing the relationship between crack tendency and crack depth, the statistical data of the dominant crack surface are obtained. Then, the number of fracture surfaces within each unit distance is counted to obtain the density distribution characteristics of the fracture surface. These steps are the basis for the study of fractured surrounding rock.
2. Because the failure of the granite specimens is sudden, the damage is gradual in the specimen before the failure. When the fissure degree in the rock develops to a certain extent, the fissure changes from a stable expansion to an unstable expansion, and then the fissure quickly passes through the rock, causing damage. Therefore, for brittle hard rock, if the support can be carried out before the fissure instability expansion, the development of fissure can be effectively controlled. For example, [PERSON] et al. [41] has carried out 3D network simulation based on deep rock joint of borehole TV, hoping to achieve the purpose of evaluating the stability of surrounding rock by simulating and exploring the distribution law of fracture space. Therefore, the fissure degree corresponding to the inflection point of maximum dissipated energy is finally adopted in this paper as the target factor to measure the support time.
3. In the study of fractured rocks, the current research is more inclined to simplify fractures into one, two, or more visible artificial fractures [26; 27; 28; 37; 38; 39], and then analyze the influence of the number of artificial fractures on rock mass deformation and failure, which can reflect the influence of fractures to a certain extent on the macro level. However, this simplified process completely ignores the influence of the interaction between disordered fractures on the evolution of rock deformation energy. Therefore, this paper adopts thermal damage to create this disordered fracture, and replaces the traditional fracture number with the crack degree. The results show that there is an inflection point of maximum dissipated energy change at the fissure degree D = (0.4-0.5). Before the inflection point, the maximum dissipated energy gradually increases, but the variation amplitude is small. This is because the consumption of plastic deformation energy at the crack tip increases during the deformation process, and the fracture development can reduce the brittleness of the sample and make the fracture in the rock more fully developed. After the inflection point, the maximum dissipated energy decreases rapidly, which is due to the development of fractures in the rock mass, which reduces the bearing capacity of the internal structure damage. Figure 12 shows the schematic diagram of the internal fracture degree of rock mass  
Figure 11: The relationship between the maximum dissipation energy conversion rate of each sample and confining pressure.  
with surrounding rock deformation. Therefore, in engineering support, when the internal fracture degree of rock mass D = (0.4-0.5), the support can be used as the basis for the identification of critical support for key parts.