Support effects of anchor bolt, shotcrete and U-steel in elastoplastic stage of surrounding rock

Analytical solutions to the complete action process of surrounding rock-support in elastoplastic stage have been provided. Supporting structures of anchor bolt, shotcrete and U-steel are commonly used in the practical projects. It is a critical theoretical issue to further study the three supporting structures on this basis. Based on the spatial effects of the excavation face, and according to the analytical solutions above-mentioned, the supporting structures respectively through project examples in which the surrounding rocks have diameters of 6 m, 5 m, 4 m, is studied. And the thesis mainly includes three the following parts: calculations of ultimate bearing capacity of the above three structures, calculation and analysis about the effect on controlling plastic deformation of surrounding rock based on the spatial effects of the excavation face, and analysis of the supporting effect on the Protodyakonov's surrounding rock pressure by the remaining supporting force. It is also studied U-steel constitutive relationship between load and displacement, proposes conception of the remaining force and analyses the mechanism of supporting structure restricting deformation of surrounding rock. Two conclusions are drawn as follows. (1) Compared with the in-situ stress(> 10 MPa), the supporting forces (< 1 MPa) provided by the three supporting structures are too low to control the elastoplastic deformation of the surrounding rock with diameters of 6 m, 5 m or more larger, but the supporting forces are effective for the surrounding rock with diameters of 4 m. (2) For the the surrounding rock with diameters of 6 m and 5 m or more larger, if the remaining supporting force can be reserved effectively, supporting structure can support Protodyakonov's pressure availably.