Research On Stability Of Tunnel Surrounding Rock Based On Multi-factor Fuzzy Comprehensive Evaluation

With the continuous development of our country's economy, railways, highways and other transportation construction projects are springing up. China is a country of many hills and mountains. In the mountains or the mid-levels districts, many roads and railways are built. In order to reduce the distance and the destruction of the. ecological environment, the tunnels are widely applied to the construction of roads and railways. In the tunnel design and construction stages, a quick and accurate stability evaluation is extremely important to the tunnels safety of surrounding rock, supporting design, construction and lately operation. So the study of tunnel surrounding rock stability has very important practical value and theoretical significance. Based on the actual tunnel projects, the analytic hierarchy process and the fuzzy comprehensive evaluation theory are studied. The method based on the multi-factor fuzzy comprehensive evaluation is used to analyze the stability of tunnel, which can accurately judge the stability of tunnel surrounding rock and provide the theory and technology support for the design and construction of tunnel.The main work and innovative results that we obtained are as follows:(1) Through analyzing and summarizing the influence factors of the tunnel surrounding rock stability, nine key factors which influence the stability of surrounding rock are obtained, such as the elastic modulus of rock mass, the cohesive force, the tunnel buried depth and so on. And the numerical simulation research of various factors under the different conditions is carried on by using the FLAC3D software. The sensitivity of the influence factors is obtained. The five factors, including the elastic modulus of rock mass, the cohesion force, the buried depth, the tunnel excavation methods and the anchor spacing obviously affect the stability of surrounding rock.(2) According to the present tunnel surrounding rock stability evaluation, the relevant theories of the multi-factor fuzzy comprehensive evaluation method are studied, which included the theory of analytic hierarchy process, the fuzzy comprehensive evaluation theory, the membership functions, the determination of the factors weights and so on. And the detail methods of the multi-factor fuzzy comprehensive evaluation are studied in the stability analysis of tunnel surrounding rock.(3) Seven typical tunnel engineerings are selected and nine influence factors of the tunnel surrounding rock stability are considered. And the value of the various influence factors is divided. Considering the general and special geological condition, the surrounding rock stability index BI summary chart of the influence factors are obtained under the different working conditions by the numerical simulation. And the fuzzy membership data are set up. The stability grade of the surrounding rock is determined by the stress ratio index BI and the relative subsidence value.(4) The multi-factor fuzzy comprehensive evaluation method is used to evaluate the surrounding rock stability of the actual tunnel engineering through the established fuzzy data of the various influencing factors. And the stability grade of the actual tunnel surrounding rock is obtained. The surrounding rock stability grade with the construction and operation of the actual tunnel engineering is compared. The research has shown that the fuzzy comprehensive evaluation method can accurately evaluate the stability of tunnel surrounding rock.