Calculation Model of Supporting System for Tunnel Under Shallow and Weak Surrounding Rock Considering the Synergistic Effects

In order to give full play to the bearing capacity of the various components of a tunnel supporting system under shallow and weak surrounding rocks, a study is conducted on the synergistic mechanism of the tunnel supporting system in these conditions. In this paper, the synergistic mechanism of the tunnel supporting system is investigated by considering each function of the supporting equipment. Then, a theoretical model is proposed to calculate the overall bearing capacity of the supporting system for the tunnel under the shallow-buried weak surrounding rocks. The ultimate calculation formula for the supporting system, which includes advanced pipe roof, leading conduit, steel arch and feet-lock anchor bolt, is obtained on the basis of the structural mechanics and elastic foundation beam theory. To validate the proposed model, the interacting forces and deformation of each support structure component are calculated respectively. Next, the calculation results are compared with those of the load-structure method and strata-structure method. Statistical analysis shows that the deformations obtained by the three methods are consistent, and that the results of each method are rather similar. It indicates that the theoretical method proposed is reliable and applicable.