Reliability Degree Of The Initial Support Of Tunnel Which Is Located In Weak Intercalated Layer

Scholars at home and abroad have been studying the reliability of structures for more than 70 years, and have achieved a lot of research results. However, the reliability research of the building(structure) of the underground space is still in the research and exploration. Especially in special geological conditions, how to establish the appropriate structural failure model and how to establish the reasonable structure of the performance function have a broad research space. This paper relies on the Lianhua village metro station of Chongqing rail transit loop line. Based on monitoring measurement and FEM simulation of subway station construction process, the change of displacement and stress around the tunnel is dynamically tracked, and the failure model of tunnel initial support is constructed. According to the statistical analysis of the effect of tunnel structure function in resistance and the effect of different influencing factors(including material parameters, geometric parameters of uncertainty), the method of designing verification points is used to calculate the subway station initial support for the reliability. The main research contents of this paper are as follows:(1) Based on monitoring measurement and the MIDAS/GTS FEM simulation of large span subway station construction process which is located in the steep dip rock with weak intercalated layer, the monitoring points are compared with the corresponding simulation points about the analysis of displacement and stress variation, and then the failure model with weak interlayer steep dip strata metro station initial support is established.(2) Through the analysis of the characteristics of the formation pressure change on the initial support, the stress value of surrounding rock under different load theory is calculated. Based on the results of FEM, surrounding rock pressure calculation value is selected properly, then reduced to linear load equivalent to shear.(3) Based on analysing the failure mode of the initial support under the layered rock, the failure model function of initial support is established, then the uncertainty of the material properties and geometrical parameters in the function is studied.(4) According to the Serial parallel theory of Reliability, and combined with the engineering practice of the construction of metro station, the reduction factor is used to calculate the reliability index of initial support. The method of designing verification points which is more practical among the calculation methods of structural reliability is selected, then is used to calculate the reliability index of the initial support of the metro station.