## 5 Discussion  
The above analysis reveals that different factors all influence the mechanical properties of bolt supports. The stress distributions of bolts are similar for different bolt diameters and lengths as well as strengths of the intact rock mass, and influences of these factors on the anchorage force are also similar. The stress distribution along such bolts in an intact rock mass is shown in Figure 24, in which the stress increases at first, then decreases along the bolt; the stress gradually increases and the peak shifts to a greater depth with the damage to the anchored rock mass. The stress distribution does not change when increasing the bolt diameter and length as well as the strength of the rock, while only the stress changes. In the meantime, the corresponding maximum anchorage force of bolts also increases.  
The fracture angle affects both the stress distribution and anchorage force of bolts in a fractured rock mass. The stress distribution along the bolts under different fracture angles is displayed in Figure 25. In the initial stage of loading, due to the small deformation of rock mass, the influence of fractures on the stress of the bolt has not yet appeared, so the stress distribution of all bolts is the same (first increasing and then decreasing). With continuous loading, the deformation of rock mass increases gradually, and the stress distribution differs with changes to the fracture angle. When the fracture angle is 90\({}^{\circ}\), the stress on the bolts tends to decrease in the fracture zone, thus forming a valley and two peak stresses, and the stress distribution curve is M-shaped. When the fracture angles are 60\({}^{\circ}\) and 45\({}^{\circ}\), the stress on the bolts in the fracture zone increases abruptly, forming peak stress, but there are two peak stresses in the former. When the fracture angle is 30\({}^{\circ}\), the influence of the fracture on the stress distribution of the bolt is weakened, and the stress distribution of the bolt is similar to that in the intact rock mass. Moreover, as the fracture angle decreases, the maximum anchorage forces of bolts decrease at first, then increase and remain less than the maximum anchorage force in an intact rock mass. When the fracture angle is 45\({}^{\circ}\), the peak anchorage force is minimized.  
Based on the aforementioned results, methods including borehole photography can be used to enhance the exploration of the internal condition of a rock mass in the subsequent design of anchoring works. If the internal structure of the rock mass is intact, the maximum anchorage force of bolts can be calculated as that in intact rock mass. If there are dominant fractures, even faults and fracture zones, in a rock mass, it becomes necessary to consider the influence of fractures on the anchorage force of bolts. In the most unfavorable case (45\({}^{\circ}\) between fractures and bolts), the maximum anchorage force of bolts is only 75% of that in an intact rock mass. After installation, the axial stress on the bolts can be monitored. According to the stress distribution obtained in the present research, if the peak on stress curves shifts to a greater depth or a valley or peak occurs and the stress increases, surrounding rocks are at risk of failure. Under such conditions, it is necessary to strengthen on-site safety management practices.  
Figure 24: Stress distribution along the bolt in intact rock mass.