Study On Construction Process Numerical Simulation And Supporting Parameters Optimization Of Tunnel

With the rapid development of expressway tunnel in China, more and more problems appear in expressway tunnel construction. For example, it is difficult to determine the support parameter and the construction opportunity between primary support and secondary lining. Taking the Daling mountain tunnel in the expressway from Guangzhou to Shenzhen port as the research object, this paper mainly discusses the optimization problem of supporting opportunity, supporting parameters and so on systematically. The main research contents as follows:(1) The finite element numerical simulation of construction process on tunnel. Combined with the nonlinear characteristic of geotechnical material, calculating theory of tunnel construction process and numerical simulation method are discussed. According to the finite element theory modeling, through confirming most of conditions, which are the design segment, physical and mechanical parameters, calculation range, boundary condition, element type, material constitutive relation, initial ground stress, the geometric model of tunnel is established.(2) The optimization problem of supporting opportunity is studied. Two mechanism, which are the deformation and failure mechanism of surrounding rock and the interaction mechanism between surrounding rock and support, are explained, and showing the necessity to choose the support timing. Then the best support time and support period are confirmed based on the physical meaning of best supporting opportunity. The finite element software ADINA is used to simulate the exploitation processes to the typical section of tunnel, the mechanical distribution and variation rules of surrounding rock, lining and bolts are got ,at the same time, the plastic deformation and the displacement distribution rules are obtained in different supporting opportunity of different load release. Finally, the best support period is determined.(3) The optimization problem of lining support strength is studied. Five scheme are made to optimize the concrete strength of primary support and secondary lining, after the force analysis, the best concrete strength of primary support and secondary lining is got, and the good support opportunity is chose from the best support period. And through comparing the force analysis of surrounding rocks, lining and bolts, the best support time is got.Numerical simulation results show that, as the lining constructed earlier, linings and anchors bear bigger load and the plastic deformation becomes smaller. Constructing the reinforced concrete lining in time can prominently control the deformation of the rock pillars and improve the stress condition of the surrounding rock. Reasonable support opportunity is beneficial to play the load-bearing ability of surrounding rock in most large degree, which making the resistance of second support system is decreased to lowest and guaranteing the using of support material is the most reasonable,and fully arouse the effect of support. Achievements from the study can guide the design and construction of tunnel with similar conditions.