# Deep Soft Rock Tunnel Perimeter Rock Control Technology and Research
## 2 Roadway Surrounding Rock Control Technology
### Analysis of Deformation of Broken Surrounding Rock in Deep Roadway  
For the deep peripheral rock tunnel with a large burial depth, under the influence of long-term high geostress, it generally shows strong creep characteristics, and it is difficult to support. This kind of soft rock tunnel in the excavation after digging very easily produces plastic deformation, as the ground stress is strong, and the support structure undergoes deformation and fracturing until destruction. Therefore, after the roadway excavation, how to apply the support structure in a timely fashion, improve the self-supporting ability of the surrounding rock, control the loosening, and inhibit the deformation, are key to the controlling the surrounding rock. For this reason, the damage mechanism of the roadway support, the distribution of the surrounding rock stress, and the creep phenomenon of the surrounding rock are inseparable and need to be studied as a whole. Assuming that the surrounding rock is uniform and that the roadway section is circular, under the action of radial stress, after a certain time \(\Delta T\), the radial creep distance of the surrounding rock is \(\delta\); then, the creep rate \(v\) of the surrounding rock is proportional to the radial gradient, as in the following Equation (1):  
\[v=K(\delta_{r}-\delta_{r0})/(r-r_{0}) \tag{1}\]  
where \(\delta_{r}\) is the radial stress in the surrounding rock at \(r\) from the center of the roadway, \(\delta_{r0}\) is the radial stresses in the surrounding rock around the roadway, \(r\) is the radial distance of the surrounding rock around the roadway, \(r_{0}\) is a point with zero distance from the center of the lane, and \(K\) is the perimeter rock creep coefficient. Therefore, in order to reduce the radial stress gradient of the surrounding rock, it is necessary to increase the bearing capacity of the support, which in turn increases the radial stress \(\delta_{r0}\) of the surrounding rock. In order to effectively control or even prevent the creep of the surrounding rock, theoretically, it is necessary to increase the radial stress of the surrounding rock around the roadway until it is equal to the original radial stress, i.e., \(\delta_{r}=\delta_{r0}\), \(v=K\). If the back of the support wall is damaged by the extrusion of radial stress \(\delta_{r0}\), then the rock becomes crushed. After squeezing into the support space, the back of the wall becomes a broken rock body, and the high stress area will be transferred to the deeper part of the surrounding rock. When the stress difference is certain, it can effectively reduce the creep rate and improve the supporting capacity of the supporting material. Creep coefficient \(K\) is a parameter that describes the physical properties of the surrounding rock, as can be seen from Equation (1); if \(K=0\), then \(v=0\), which indicates that the surrounding rock is a stable rigid body and does not need any support. The larger the  
Figure 1: Relationship curve between the deformation of the roadway enclosure and the support resisting force. value of \(K\), the stronger the creep of the surrounding rock. Therefore, the value of \(K\) has an important influence on the creep rate of the surrounding rock.