| Surrounding rocks of large cross-section tunnel in soft ground are belong to soft fractured rock, of which the complex surrounding rock stress distribution as well as deformation condition bring lots of problems to tunneling construction design and high requirements for safety of tunneling construction. Collapse failure of tunnels will happen once the method was chose improperly or the parameters of supporting were designed improperly. Thus, there is significant and practical meaning in studying the influence of different excavation method and supporting parameters of large cross-section tunnel on the deformation and stress of surrounding rocks in soft ground.Based on the engineering background of Fuyan I in passenger dedicated line of Jituhui Railway, methods of investigation of tunneling construction home and abroad as well as numerical simulation were applied to research different excavation method and supporting parameters of large cross-section tunnel in soft ground. Reasonable excavation method and supporting parameters were proposed in order to provide reference for the later similar tunneling construction. The main aspects were studied in the paper:(1) Understanding the present situation of development, relative construction method and supporting method by referring to relative document literature home and abroad aiming at providing support for the later research.(2) Discourse of frequently-used method of large cross-section tunnel construction in soft ground as well as comparison of their applicability were carried out. Combing with design materials of practical construction, three step seven step method and CD method were chose as compared construction methods through the investigation and analysis of tunneling construction in soft ground home and abroad.(3) Large universal finite element software were applied to numerically simulate the whole process of three step seven step method and CD method of large cross-section tunnel in soft ground. The stress, displacement as well as the stress characteristics of the whole supporting structures were comparatively analyzed to obtain the suggestion that three step seven step method was more suitable in this ground condition, which provide reference for the later similar tunneling construction.(4) Based on the application of three step seven step method, stress condition of steel arch with different types, different distances was studied according to allowable stress rules and the most suitable supporting plan of steel arch was selected at the premise of satisfying the safety of tunneling construction. Reasonable parameters of pipes were selected by studying the influence of parameters of pipes on the displacement, stress of surrounding rocks as well as internal force of pipes. Providing technical guidance of supporting plans selection in similar ground conditions in the future through the investigation of parameters changing of steel arch and pipes. |
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