## 1 _Article_  
### Evolution Characteristics of Plastic Zone in Jointed Rock Mass of High-Temperature Hydraulic Tunnel  
**[PERSON] 1**, [PERSON] 1,2,*, [PERSON] 3,4 and [PERSON] 1,5  
support resistance on the range and morphology of the plastic zone in rock mass through a theoretical analysis and numerical simulation. [PERSON] et al. [7] revealed that the plastic zone morphology of homogeneous rock mass under different confining pressure conditions can be circular-, elliptical-, and butterfly-shaped. A formula was derived to calculate the morphology coefficient, and the morphology characteristics of the plastic zone can be distinguished with this coefficient. [PERSON] et al. [8] used the convergence constraint method (CCM) to evaluate the convergence of tunnels and the rationality of support, obtaining 10% and 4% higher predicted values of plastic zone and tunnel convergence range than those obtained using conventional methods. [PERSON] et al. [9] derived analytical formulas for the range of the fracture zone and plastic zone of the rock mass under a uniform stress field using the elastic-plastic theory. [PERSON] et al. [10] found, based on the finite difference software simulation, that the plastic zone expansion angle under non-uniform in situ stress conditions is approximately constant. These achievements have contributed considerably to understanding the evolution characteristics of plastic zones in an intact rock mass. However, natural rock mass often has joint fissures, and the distribution pattern of plastic zones in it is inevitably different from intact rock mass [11; 12]. [PERSON] et al. [13] discovered through indoor experiments, on-site measurements, and numerical simulations that the tensile strength of rock mass is related to the joint dip angle, and the joint dip angle has an impact on the development degree of the plastic zone in the rock mass. In addition, because rock masses are often in a complex mechanical environment, studying the plastic zone evolution characteristics of the jointed rock mass under a multi-field coupling effect is of great importance [14; 15; 16], especially for high ground temperature disease, which is one of the causes of instability in rock mass. [PERSON] et al. [17] studied the effects of thermal degradation on the compressive strength, ultimate compressive strain, color, and mass loss of four limestone blocks from the Yucatan Peninsula. [PERSON] et al. [18] studied the influence of ground temperature on the characteristics of rock mass and conducted conventional triaxial compression tests under different temperatures and confining pressures using acoustic emission technology to analyze the damage and stress. The results showed that the peak strength, loudest emission energy, britteness, and other parameters of granite increased at a temperature of lower than 60 \({}^{\circ}\)C, while those all decreased when the temperature raised to higher than 60 \({}^{\circ}\)C. Based on physical model experiments and FLAC3D numerical simulation, [PERSON] et al. [19] analyzed the influence of a high geothermal gradient and high internal water pressure on the safe bearing capacity of rock mass and revealed that the damage degree and cracking depth of tunnel rock mass increased with the increase in the temperature gradient, internal water pressure, and linear expansion coefficient of the rock mass. In order to better understand how periodic fluctuations in surface temperature can lead to rock failure, [PERSON] et al. [20] conducted thermal and strain monitoring activities on selected quarry walls and conducted experimental testing sites on connected rock blocks. These studies either focus on the plastic zone of jointed rock mass under the action of a single stress field or on the plastic zone of an intact rock mass under the thermal-mechanical coupling effect, whereas there are few studies focused on the plastic zone of the jointed rock mass under the thermal-mechanical coupling effect.