## 4 Results and Discussion
### Effect of Temperature on the Axial Force and Shear Stress on the Interface of Specimens  
Analysis of temperature effects on the distribution of axial force and shear stress of the anchorage section was achieved by changing the physical and mechanical properties of anchorage material. The ratio of elastic modulus in forming the medium of anchorage system has a large impact on the value and the distribution form of axial force and shear stress of the rock bolt. When the value and the distribution of axial force and shear stress of the anchorage body under the action of high temperature were analyzed, the data of four representative groups whose tensile force were 10 kN, 30 kN, 70 kN, and 90 kN were chosen, and relevant analyses were carried out.  
(1) Effect of temperature on axial force  
From Figure 9, it can be seen that, under the same tensile force, with an increase in environmental temperature, the axial force along the length of the anchorage body decreases more slowly. Decay law along the length of the anchorage body is the slowest at an environmental temperature of 50 \({}^{\circ}\)C, followed by axial force at 35 \({}^{\circ}\)C and 20 \({}^{\circ}\)C. With an increase in temperature, the axial force at the same place from the pull end of the anchorage body becomes larger.  
Figure 9: The distribution diagrams of axial force under different tensile force. (**a**) Tensile force is 10 kN. (**b**) Tensile force is 30 kN. (**c**) Tensile force is 70 kN. (**d**) Tensile force is 90 kN.  
Effect of temperature on shear stress  
From Figure 10, it can be seen that, under the same tensile force, with an increase in temperature, the decay law of shear stress along the length of anchorage body becomes slower. At the point near the pull end of the anchorage body, with an increase in temperature, the maximum value of shear stress becomes smaller which means the interface bond strength between rock bolt and grouting body decreases gradually. With an increase in temperature, when the depth exceeds a certain value along the length of the anchorage body, the shear stress at the same point increases gradually, which means the distribution of the shear stress along the length of the anchorage body becomes more uniform.  
It can be seen from the above result that the axial force and shear stress all gradually decreased from the pull end to the non-pull end until they became zero. High temperature has little influence on the fully grouted rock bolt used in tunnel support construction with high geothermal activities. If the surrounding rock is a kind of nonabsorbent rock, the surrounding rock will prevent the evaporation of water in the process of cement hydration. If the surrounding rock is absorbent rock, water will evaporate, which will affect the performance of the anchorage system. Thus, it is very important to take measures to avoid the evaporation of water during the strength growth process in future anchor construction.  
The anchorage system is a heterogeneous material. The stress distribution is not to be linear, with the maximum load at the rock bolt head and zero stress not at the end. The point of zero stress is called the critical point. The critical length is different because of a different diameter, the roughness of the rock bolt, and a different strength of grouting material. Therefore, it is suggested that the design length of the rock bolt be longer than the critical length.