| Carbonaceous slate belongs to soft rock, the large deformation of tunnel soft rock is a problem in the prevention of tunnel diseases. Experts and scholars at home and abroad have been doing research continuously, the control theory of tunnel large deformation has been continuously developing. In the actual project, many methods to control large deformation have also been created, and made good achievements.This dissertation takes the Zhifang tunnel of Lanzhou-Chongqing railway as the background, the deformation laws and deformation characteristics are investigated, the deformation causes and control mechanism are analyzed. According to the engineering features of the tunnel being investigated, the causes are analyzed to find the key to solve this problem, the engineering measures to control tunnel large deformation are taken out.In order to research the control method to deal with tunnel large deformation, this dissertation discusses the stability control theory of tunnel large deformation, analyzes the relationship between tunnel support and surrounding rock stability of soft rock, which does a detailed comparative study on the function of different types of support structures to control deformation.The three-bench seven-step excavation method and two-bench five-step are mainly as the excavation method. The numerical simulation and comparative analysis are made for the three-bench seven-step excavation method and two-bench five-step excavation by 2D finite element method in the fifth chapter.The numerical simulation for the two different excavation and support methods is made by 3D finite element method in the sixth chapter, in order to get a reasonable excavation and support method to control the tunnel large deformation. |
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