Study on mechanical characteristics of large section tunnel construction in soft surrounding rock

The construction of large section tunnel in soft stratum will lead to large deformation, and poor control measures will lead to instability or collapse of the face, resulting in serious safety accidents and heavy economic losses. In order to thoroughly study the mechanical characteristics of large section tunnel construction in soft surrounding rock and optimize the construction scheme, similar model tests were carried out for the dependent projects in this paper to analyze the evolution law of stress and displacement during tunnel excavation. At the same time, the numerical simulation method is used to summarize the mechanical characteristics of the tunnel support structure, and the real action of the system bolt is proposed. The construction optimization scheme was verified by field test. The results show that the horizontal control effect of the support structure on the surrounding rock is much greater than the vertical constraint effect. The tensile stress of the system bolt is small in the excavation process, and its role in controlling the deformation of the tunnel is very limited. Its main function is to serve as a certain safety reserve in the design process.