Study On Dynamic Construction Mechanics Of Different Excavation Methods Of Highway Tunnel

Based on Shitang tunnel project of Cheng Wan2class highway, the project profile gives a brief introduction and comprehensive analysis on numerical simulation of dynamic construction and dynamic construction mechanics effect. By ANSYS10.0FEM software, numerical model of the shallow-buried portal section and numerical model of hole body fracture zone were established. CRD method was used o simulate the tunnel excavation works in the shallow-buried portal section, and detailed analysis of the dynamic mechanical properties of construction; CD method was used to simulate the tunnel excavation in the hole body fracture zone, and detailed analysis of the dynamic mechanical properties of construction; The step method was used to simulate tunnel excavation works in the out of shallow-buried portal section, and detailed analysis of the dynamic mechanical properties of construction.With the CRD numerical simulation method of entrance shallow buried section,the paper shows main conclusions are follows:Firstly, It is safe and feasible to use CRD method into entrance excavation, The method is clearly controlled the hole week, and effective control of surrounding rock mass plastic zone development; Secondly, the stress concentration region mainly appear in a shallow rock around the left and right foot arch, this is also the main surrounding rock mass plastic zone.Through the CD numerical simulation method of the deep broken body section, the main conclusions in this article are as follows:Firstly, It is safe and feasible to use CD method for buried the broken section, This method effectively limits the development of vault displacement, keep surrounding rock mass plastic zone effective within a reasonable range. Second, surrounding rock stress concentration occurs mainly in the region around tunnel arch, this is also the main surrounding rock mass plastic zone. Thirdly, The sprayed concrete axial force of the first guide hole is larger than the subsequent guide hole. it is recommended that when you select CD or CRD method in tunnel construction, to improve the primary support of the first guide hole, lowering down the primary support of the subsequent guide hole. Fourthly, The key point of construction, CD method and CRD method,is the stability of the temporary wall, which showed a larger internal force in the subsequent construction process. For security reasons, it is necessary for temporary middle wall and temporary Invert for the conduct for strain monitoring. Through step numerical simulation method of the out of shallow-buried portal section, the main conclusions in this article are as follows:Firstly. It is safe and feasible to use CD method for shallow-buried portal section, the method is simple and fast. Secondly, surrounding rock stress concentration occurs mainly in the region around tunnel arch, this is also the main surrounding rock mass plastic zone. Thirdly, the maximum of bolt axial force appear near the arch, shows lock foot anchor plays a larger role, it must be made to ensure the construction quality.Combination of field monitoring data, to research and analysis the characteristics of surrounding rock and stress characteristics of supporting structure of Shitang tunnel, drew some useful conclusions.