Study On Schemes Of Tunnel Portal At Landslides Of Mountain Expressway

Along with the rapid development of communications and transportation recently in China, especially a great number of constructions of expressway with tunnels have been constructed in the central and western regions. The length and cross-section of the tunnels are unprecedented. The difficulty also becomes greater. The depth of embedment at the tunnel portal is shallow. The degree of weathering of surrounding rock is serious, and the geological conditions are complicated. Therefore it is difficult to deal with the landslide at the tunnel portal and choose a rational scheme. Taking Shiman Expressway construction as an example, the portal schemes of expressway at the landslide are studied in this thesis. Firstly, the design terms, the forms and selection principles, the construction methods and construction methods of the tunnel portals are introduced in detail. For the special geological conditions, the auxiliary construction schemes are also studied. The main design parameters of the auxiliary construction are illustrated.Secondly, the process of the landslide of Lishiguan Tunnel is presented. It is taken place in two times and the scale became larger and larger. The landslide is forecasted by the monitoring data of ground surface and internal tunnel in time. The reasons of the large scale landslide is analyzed and some useful suggestions are given.Finally, the slope stability of Lishiguan Tunnel is simulated by ANSYS using the elasto-plastic finite element theory and strength-reduction theory. These included the case where the landslide was not happen and the case after the treatment of the landside. The deformation, failure mechanism and evolution process of the slope under the gravity are analyzed. The influence of the yield criterion and flow law is considered. At the same time, the useful roles of the retaining wall for increasing shear strength of the base and improving the stress condition are studied through the time-history results postprocessor.According to the unfavorable geological conditions at the portal of the tunnel, an economical and workable scheme is presented. The study has not only solved the difficulties in the practice, but also gives some useful references for the similar constructions. The research results may make the design and construction of tunnels be safer, more reliable and more economical.