Large Span Tunnel Construction Methods Optimization Analysis And Construction Response Research

This paper is based on the background of rapid development of subway construction in China and comprehensive use of technical research,theoretical analysis,numerical simulation,field testing and other means.Many jobs including optimization of super large section tunnel excavation method and simulation of super large section tunnel construction process and monitoring surrounding rock stability in the construction of super large section tunnel are studied systematically and deeply.The main research work and results are as follows:(1)Through analyzing the principle of benching tunneling method,a uniform horizontal layered model is constructed.This model can be effectively explained by adjusting the number of layers and the height of the steps,such as the three steps tunneling method.Besides,the AHP method is used to select the optimal excavation scheme based on optimization example,considering the surface subsidence,face extrusion,the difficulty of construction and excavation and so on.(2)Through the analysis of the common construction methods of CD method and CRD method and the analogy of horizontal layered model,a uniform transverse block model is constructed.This model can effectively explain and optimize the various transverse block by adjusting the number of lateral blocks and the width of blocks.(3)Through combining the advantages of a uniform horizontal layered model and a uniform transverse block model,a uniform plane partition model is constructed.The model can be achieved by the number of layers,the number of lateral blocks,the height of the steps and the width of blocks to explain all the problems of plane optimization of the four parameters at the same time,and when i=2,j=2,the plane partition model by using the dynamic programming theory(DP)are used to optimized for example.(4)Through the analysis of the problem of excavation footage and the analogy horizontal layered model and transverse block model,a common longitudinal segmentation model is constructed.This model can be used which is based on the main parameters of the number of sections and the length of sections,at the same time optimization scheme can be based on AHP analysis.(5)Through combining the advantages of a uniform plane partition model and a common longitudinal segmentation model,a uniform three dimensional model is constructed.The model can be explained and used for all tunnel excavation methods and optimization problems.All the construction methods can be explained by adjusting the six parameters including the number of layers,the number of lateral blocks,the number of sections,the height of the steps,the width of blocks and the length of sections and the tunnel excavation method can be optimized.(6)Through combining the respective advantages of the theory of dynamic programming(DP)and analytic hierarchy process(AHP)of,with the problem of the large section tunnel excavation method optimization,with the DP_AHP method the multi-objective problems of tunnel excavation can effectively be carried out,together with optimization and decision-making,and finally the optimized construction scheme can be put forward.(7)In this paper,the numerical simulation of the excavation of large section tunnel of Chongqing Metro Line 10 in Central Park East is carried out.Through the displacement field,stress field and plastic zone,the stability and deformation of surrounding rock are analyzed.And it founds that the optimization of the construction method to meet the construction requirements.(8)Through the construction monitoring the large section tunnel construction of Chongqing metro line ten Central-Park-East station with the 9 step excavation method,the monitoring results and numerical simulation results were compared and analyzed.The results show that the optimization methods of the old 9 step excavation method are effective and the deformation law is the same and the deformation quantity is at the same level.