After the excavation of roadway, support of working face decreases roof subsidence and deformation. Installing rock bolt at this time has good effect in controlling stratum’s separation and slide. Prestressing force becomes bigger when rock bolt was installed in time, the integral stiffness of stratum is higher, it is in a state of compression and the effect of support is more evident.
The mechanism points of rock bolt’s supporting effect are as following:
1. The main function of rock bolt is to control surrounding rocks’ separation, slide, fracture, deformation and damage, make stratum in pressured state, keep surrounding rocks’ integrity and enhance intensity and stability.
2. A secondary bearing structure with great rigidity is formed in anchoring region, which restrains separation layer outside and improves stress distribution in deep position.
3. To achieve above supporting effects, the supporting system of rock bolt is important, especially the prestress force of rock bolt. Confirming reasonable prestress is the key for supporting design. Of course, higher prestress demands higher intensity of rock bolt.
4. The diffusion of rock bolt’s prestress is also important. The effective range of single rock bolt’s prestress is limit, it should combine with other accessories to diffuse into further stratum.
5. Rock bolt should be installed once to control deformation and damage effectively, ignoring supporting twice and roadway maintenance.