## 5 Discussion  
According to the above analysis, the deformation and damage of the II5 Rail Rise mainly resulted from high stress, low rock strength, and the continuous development of deep and shallow cracks. This conclusion is consistent with the research results in the literature [30]. They believe that the damage process of crack initiation, crack propagation, and rock separation in the surrounding rock develops gradually from the shallow to the deep, and ultimately leads to the instability of the surrounding rock. Furthermore, they proposed a combined support scheme of a \"bolt-cable-mesh-steel ladder\". As the stress environment of the roadway hardly changes, the control technology shall be aimed at rock strength improvement and crack reduction. High-preload anchor bolts can well improve the rock strength and limit the development of internal cracks in the rock, and crack filling can improve the occurrence environment of the surrounding rock, raise the rock strength, and improve the stress state of the support body. For this roadway, a control technology of high-preload bolt + deep- and shallow-borehole crack filling was proposed. Its reinforcement principle is as follows: (1) The high-preload bolt support can inhibit the development of shallow cracks and improve the bearing capacity of the shallow surrounding rock. (2) The shallow-borehole low-pressure crack filling seals the shallow cracks as the slurry is thrust into or penetrates the cracks, further reducing the fragmentation degree of the shallow surrounding rock and cementing the surrounding rock surface into a stone body with high bearing capacity. This not only ensures the integrity and bearing capacity of the shallow surrounding rock, but also endows the broken surrounding rock with the ability to withstand high pressure. (3) The deep-borehole high-pressure crack filling in the deep surrounding rock enhances the permeability of the injected slurry in the deep surrounding rock and lowers the crack density of the deep surrounding rock, thus realizing the replacement between the slurry and the cracks. Finally, a homogeneous continuous high-strength reinforcement body is formed. The reinforcement body can provide effective anchor points for anchor bolts in the shallow surrounding rock and anchor cables in the deep surrounding rock, hence achieving active support and expanding the bearing range of the support system. Compared to the control technology proposed in the literature [30], this technology adds deep- and shallow-borehole crack filling, which has a stronger inhibitory effect on crack propagation. Based on the above control ideas, anchor bolts were simulated using the Rockbolts element and anchor cables were simulated using the Cable element in the established engineering model. The surrounding rock control effect of the high-preload anchor bolt + deep- and shallow-borehole crack-filling control technology was briefly calculated and analyzed. Figure 15a exhibits the average deformation of the two ribs of the controlled roadway. Although the displacement of the right rib was greater than that of the left rib, their deformations differed by merely 20 mm after stabilization. Both ribs experienced secondary deformation and displayed obvious rheological deformation properties during the secondary deformation. The amount and duration of the decelerated deformation of the right rib were greater than those of the left rib in the secondary deformation, but the final stabilized deformation amounts of both ribs were relatively small. Figure 15b presents the average deformation of the roof and floor of the controlled roadway. Although the roof and floor experienced secondary deformation, the deformation amounts were both less than 10 mm. The roof and floor entered the stabilized deformation period on the 150 th day, during which the displacement rate fluctuated at around 0.01 mm/d, with slight surround  
ing rock deformation.