Stability Of Surrounding Rock And Reliability Analysis Of Supporting Structure Of Super Large Span Flat Underground Chamber

At present,super-large span underground tunnels(caverns)have been used more and more in the construction of transportation and water conservancy infrastructure in our country,but their design and construction process mainly refer to similar projects or small and medium-sized span tunnels(caverns)design methods,resulting in a large difference between the calculation results and the actual situation.In addition,the failure mode of surrounding rock,the calculation method of surrounding rock pressure and the reliability of supporting structure of super-large underground tunnel(cavern)also need to be studied.This paper uses numerical simulation and theoretical analysis to study the failure mode,pressure calculation and reliability analysis of the surrounding rock of the super-long tunnel(cavern).The main research work and achievements are as follows:(1)Taking super large span tunnel(cavern)as the main research object,based on the existing design specifications,the numerical simulation method combining finite element and discrete element is adopted to analyze the deformation and failure characteristics of the surrounding rock of the super large span tunnel(cavern),considering the influence of different buried depth,surrounding rock grade,side pressure coefficient,vector span ratio and other factors.Two failure modes of surrounding rock of super long span tunnel(cavern)are put forward,and reasonable excavation design schemes are suggested.(2)Based on the two failure modes of surrounding rock obtained by numerical simulation,the upper limit theory of plastic limit analysis is used to derive the formula for calculating the pressure of surrounding rock of super long highway tunnel;Based on three rock failure criteria,linear Mohr-Coulomb,nonlinear Mohr-Coulomb and HoekBrown,the influence of relevant parameters on surrounding rock pressure is analyzed,and the rationality of the deduced surrounding rock pressure formula is verified by comparison and analysis with the existing calculation formula and numerical simulation results.(3)With the help of R language in the field of statistical analysis,Copula sampling method(CBSM)is used to study the reliability of the support structure of the ultra-large span tunnel(cavern)based on the dispersion and correlation analysis of the physical and mechanical parameters of the surrounding rock,and the influence of the distribution characteristics of the physical and mechanical parameters of the surrounding rock on the reliability of the support structure is defined.The feasibility of using R language and R language program package Vine Copula to analyze the reliability of underground engineering structure is verified.The research results of this paper have important reference value for excavation,pressure calculation of surrounding rock and reliability analysis of support structure of super large span tunnel(cavern).