## 1 Introduction  
As an important support method in tunnel engineering, rock bolt supports are widely used in design and construction. When rock bolts are applied in a geothermally active tunnel, a series of physical and chemical reactions can arise affecting the anchorage system. These reactions may lead to bond behavior degradation and structural damage to the anchorage body, thus compromising the durability and safety of the entire tunnel structure. Therefore, there is a need to study the effects of temperature on bond behavior of the anchorage system's interface. Anchorage performance in the system mainly depends on interfacial bond strength between the rock bolt and grouting body, and on the strength of the rock bolt rod body. In this context, the complex nature of interfacial bond strength is therefore the focus of this study of the anchoring system. In the exploration of stress characteristics of the rock bolt's interface under the action of the tensile load, it is generally accepted at present that frictional resistance of the anchoring section is not evenly distributed along the length of the rock bolt. Moreover, maximum shear stress appears near the orifice. Frictional resistance appears to have nonlinearly decreasing distribution along the rock bolt rod body [1]. However, there is no unified conclusion about the specific distribution of shear stress. In 1970, [PERSON] [2] proposed a formula for the distribution of friction resistance along the length of a rock bolt according to the power function. According to the formula, frictional resistance at the external end of the anchorage body was the maximum frictional resistance. After many experiments, it was found that this feature did not agree with field measurements. Based on the displacement solution of Mindlin, supposing that the adhesive material and that the rock and soil mass were the same kind of elastic material, [PERSON] [3] derived an elastic solution for shear stress distribution of an anchorage body. [PERSON] and [PERSON] [4] established a hyperbolic function model for the load transfer of bolts and derived a calculation formula for the distribution of frictional resistance and shear displacement along the length of a rock bolt. On the supposition that a whole anchorage system is in an elastic condition, and considering the axial stress distribution on the rock bolt, [PERSON] et al. [5] derived a calculation formula for the shear stress along the length distribution of a rock bolt. In order to better reflect the nonlinear and softening characteristics of the relationship between shear stress and shear displacement of an anchorage interface, [PERSON] and [PERSON] [6] established a composite exponential-hyperbola nonlinear shear slip model. Based on that model, interfacial mechanical characteristics for the whole system, from the elastic stage to the rock and soil mass interface slip of the anchored section, were analyzed. [PERSON] [7] established a shear slip model of a double exponential curve of an anchorage interface by analyzing the characteristics of the relationship between shear stress and the shear displacement of the load transfer of the anchored section. [PERSON] et al. and others [8; 9; 10; 11] carried out many theoretical analyses and experimental studies on the mechanical principles and anchorage mechanism of the rock bolt. [PERSON] et al. [12] derived the rock bolt interface shear stress produced by the deformation of the surrounding rock, taking the displacement of rock as the functional parameter, thereby allowing the location of the neutral point and axial force distribution of a fully grouted rock bolt to be determined. Based on the damage characteristics of rock and soil under the action of shear stress and the load transfer mechanism of rock bolts in rock and soil mass, [PERSON] et al.