Numerical Simulation Research On Mechanical Characteristics For Asymmetric Multi-arch Tunnel And Structure Optimization

With the rapid development of transportation in our country, the highway tunnel number increase gradually. In mountainous narrow area, it’s difficult to connect the tunnel and the road outside when the clear distance is more than15m to30m as the specification requires, especially each connected tunnels and underground tunnel engineering. Asymmetric multi-arch tunnel is a special kind of structure form under particular condition. On the research background of the National Sci-Tech Support Program-"The integration and demonstration of urban underground space development application technology", and taking the bifurcated multi-arch tunnel section of the underground road as the research object, this thesis studies the surrounding rock pressure calculation method, the structures mechanical features and the mechanical characteristics of the asymmetric multi-arch tunnel. Mainly includes the following content:1. Based on the pressure-arch theory and the particularity of asymmetric multi-arch tunnel structure, the thesis contents the derivation of deep buried asymmetric multi-arch tunnel surrounding rock pressure calculation formulas. Based on the Xie Jiaxiao theory and the particularity of asymmetric multi-arch tunnel structure, the thesis contents the derivation of shallow buried asymmetric multi-arch tunnel surrounding rock pressure formulas. Meanwhile, by the comparison of numerical simulation results and theoretical results, it verifies the rationality of the deep/shallow buried asymmetric multi-arch tunnel surrounding rock pressure calculation formula that derived.2. The thesis simulates and analyses the load-structure model of asymmetric multi-arch tunnel in ANSYS, and analyses the mechanical properties of the asymmetric multi-arch tunnel structure under different middle wall thickness.3. The thesis simulates and analyses the stratum structure model of asymmetric multi-arch tunnel in FLAC3D, and analyses the dynamic mechanical characteristics of construction under different construction sequence in tunneling.4. The thesis gives the comparative analysis about the two construction methods: MLRM and MRLM in the respects of the surface subsidence value, arch sedimentation value, typical position displacement and stress of supporting structure, typical position displacement and stress of mid-board and plastic zone. 5. According to the characteristics of asymmetric multi-arch tunnel section, the thesis presents the section optimization model based on the complex method. And it also conducts an optimal design for the middle section of the bifurcation tunnel multi-arch section.