Research Of Engineering Geological Features And Tunnel Stability In Changchun Subway

In recent years,the construction of subway is enjoying a boom with the rapid development of the city and the expansion of the population.In the process of domestic subway construction,some large cross section shallow tunnels successively appeared.The systematic study of the large cross section shallow tunnels has important theoretical value and actual meaning because of the complexity and particularity of the tunnel mechanical behavior.By theoretical research,qualitative analysis,numerical simulation and monitoring in site and other means,linking to the tunnel of Changchun subway,some research works were done centering on the influence factors and stability of the surrounding rock in shallow buried large section tunnel:(1)Theoretical study of surrounding rock stability in Large cross section shallow tunnel: The theoretical research of the large cross section shallow tunnel concluded that its stress distribution accords with the oval cross section tunnel approximatively.The stability of the surrounding rock in large cross section shallow tunnel influenced by the natural stress state of rock and soil,is not only related to the rate between horizontal stress and natural stress,but also related to the flat rate of the tunnel.(2)Qualitative analysis of surrounding rock stability based on threedimensional geological model visualization: Using the visualization technology of three-dimensional geological model and geological exploration to analyze the stability of the surrounding rock qualitatively,the tunnel across the region geological structure features,mechanical properties and the characteristics of the stability of surrounding rock,the geological structure features and mechanical properties of the tunnel across region and the characteristics of the stability of surrounding rock are revealed.The research results show that use threedimensional geological model visualization techniques to qualitative analyze the surrounding rock stability is practical,intuitive,and fast.(3)Three-dimensional simulation interface program design: Through analyzing the structure rules and data formats of GOCAD and FLAC3 D software,the interface program of two software is wrote by using computer programming language.It realizes the transformation between three-dimensional geological model and numerical calculation model,solves the FLAC3 D complex geological body modeling problem,achieves the complementary advantages of GOCAD software and FLAC3 D software,provides the recommended reference for followup mining engineering,geotechnical engineering and water conservancy and hydropower engineering complex geological body modeling and calculation analyzing.(4)Surrounding rock stability analysis based on different factors: The threedimensional numerical simulation was conducted by various surrounding rock,construction methods,flat rate and various excavation.The change characteristics of displacement field and stress field of surrounding rock were opened out.The security,economic and fast construction method and excavation and the design optimization scheme of low flat rate tunnel were given.(5)High precision simulation calculation analysis: Through the high precision simulation calculation for the proposed tunnel,the change characteristics of displacement field and stress field of surrounding rock,vault crown settlement,clearance convergence and arch bottom uplift were concluded,the applicability and recommendation of the high precision simulation calculation analysis were verified.Many aspects of stability research of large cross section shallow tunnel are studied in this paper.Such as tunnel mechanical characteristic analysis,influencing factors analysis of the surrounding rocks stability,the visualization technology analysis of three-dimensional geological model,simulation interface program design,comprehensive analysis by using numerical simulation and field monitoring.Works are systematic and complete,which can provide experience for the future similar projects.