| Karst exists extensively in China, it's a kind of poor geology conditions which affect the construction and operation of road tunnels seriously. Study on the influence of karst upon the stability of tunnel surrounding rock and support structure has directly impulsed the construction of karst tunnel.According to Pingyang tunnel and Tianchi tunnel,the influence of concealed caverns on the stability of tunnels in Karst region is researched,while the mechanical characteristics of secondary lining and the structure design of tunnel in abundant water and karst zone are studied detailedly,which mainly contains as follows:Firstly, construction process of Pingyang tunnel in tectonic and corroded region is numerically simulated with elasto-plastic FEM by using ANSYS 10.0 software, then the influence of concealed caverns on the stability of tunnel is analyzed.Secondly, the research of external hydraulic pressure on tunnel lining structure is summaried. The mechanical characteristics as well as safety factors of the secondary lining of Tianchi tunnel under different external hydraulic pressure are studied.Lastly, the stability of lining structure with different thickness and section of Tianchi tunnel is analyzed with elasto-plastic FEM. The mechanical characteristics as well as safety factors of the secondary lining structure under different external hydraulic pressure are studied detailedly.The main results of numerical simulation are as follows:1. The stability of surrounding rock and support structure discrease distinctly because of the karst cave in the bottom of the tunnel,so the geological prediction must be carried out before the tunnel excavation construction, and the advanced support is imperative for the safety of the tunnel with karst caves.2. The inner forces of the secondly lining structure increase with the raise of external hydraulic pressure, the bending moments of the corner of the invert arch increase largely, and its eccentricity is biggest while safety factor is smallest.3. The best optimization design of the lining against external water pressure is increasing the radius of the corner on the invert arch (keep the center point constant)... |
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