Study On Dynamic Emulation On NATM Construction Processing DaPingLi Tunnel

With the acceleration of implementing the Great Western Development Strategy, constructions of highway tunnel will be more. And the excavation of tunnels and underground engineering which continuously changes in time and space is a dynamic process. Therefore, research on the structural stability of country rock and support is meaningful and of practical significance to highway tunnel excavation.This paper firstly give a summary of the development of mountain tunnel construction method,especially NATM;then summarizes numerical simulation of the excavation process;and then systematically explain the mechanics theory, behavior and characteristics in the process of excavating the tunnel and underground engineering.Secondly, depending on a long DaPingLi tunnel, based on two different work conditions, the construction process of K23+900 tunnel section is simulated by means of the method of the application of initial ground stress load according to plane strain problem analysis. By comparing and analyzing the stress and strain of ground rock at the two construction process, some conclusions are as follows: As far the deep tunnel, the bench method construction is no apparent advantage; however, if the property of ground rock is poor, the bench method construction significantly superior to the full face method construction. Thirdly, based on the different excavation options, The change process of the stress and strain of ground rock, initial support and secondly lining at the construction process of K23+900~936 tunnel section is simulated by means of the method of multi-load step according to the special problem analysis. There are some conclusions after comparative analysis: no matter what kind of excavation, the first excavation tunnel makes more perturbation to ground rock than the subsequent excavation tunnel does; if the synchronous excavation in the same direction is adopted, the maximum vertical displacement of arch crown will appear at the meeting of tunnel, and the method is superior to the synchronous excavation in the opposite direction. Fourthly, research on the interaction between initial support and second lining of K33+800 tunnel section is made according to elasto-plastic plane strain, some laws drawn are as fellows: there is a uneven pressure between initial support and secondly lining, but the pressure change trend is affected by the structure type of tunnel lining, and second lining is regarded as the main load-bearing tunnel structure.Finally, according to the excavation characteristics of DaPingLi tunnel and some problems solved, preliminary scheme proposals on excavation advance prediction are formulated.