Study On Influencing Factors Of Stress And Strain Of Long Span Diversion Tunnel

In recent years, the design and construction of the large-span tunnel in China is more, and the diversion tunnel of single hole develops bigger and bigger. Through grope and practice, he design and construction of the large-span single-hole tunnel in China has made great progress, reached the international advanced level. But the geological conditions and operating conditions is complex, the large-span small-distance tunnel surrounding rock group which should be related results of deformation and stability studies are not much, and the construction experience is less useful. Therefore, the paper presents an example of a hydropower station on the right bank diversion tunnel of the large-span small-clear distance tunnel stress strain influence were analyzed, it is concluded that the diversion tunnel surrounding rock stress and strain change rule, which can provide reference for other similar tunnel design and construction. The main results are as follows:(1) The engineering geological conditions (including topography, lithology, geological structure, weathering unloading) and hydrogeologic conditions (including groundwater development and climate characteristics) of the hydropower station right bank diversion tunnel are analyzed, the basic characteristic of the right bank diversion tunnel is determined, and choose the most unfavorable section of the engineering geological conditions, which can provide the basis for three-dimensional numerical analysis model.(2) Studied the influence of different depth of surrounding rock stress and strain of the diversion tunnel:three-dimensional numerical model of the single hole excavation of the large span tunnel is established:when depth is different, the tunnel excavation process is simulated by using the full section excavation method, it is conclusion that the diversion tunnel surrounding rock stress and strain change rule.(3) Studied the influence of different excavation method of surrounding rock stress and strain of the diversion tunnel:three-dimensional numerical model of the single hole excavation of the large span tunnel is established:based on the three-dimensional numerical model of the single hole excavation of the large span tunnel which has been existed, the tunnel excavation process is simulated by using face excavation method and partial excavation method, it is conclusion that the diversion tunnel surrounding rock stress and strain change rule.(4) Studied the influence of different excavation sequence of surrounding rock stress and strain of the diversion tunnel:the three-dimensional numerical model of the large-span small-clear distance tunnel excavation group is established, the tunnel excavation process is simulated by using four kinds of working conditions, it is conclusion that the diversion tunnel surrounding rock stress and strain change rule.(5) Studied the influence of groundwater seepage of surrounding rock stress and strain of the diversion tunnel:based on the three-dimensional numerical model of the large-span small-clear distance tunnel excavation group which has been existed, combining the theory of fluid-structure interaction, it is established that can consider the numerical model of groundwater seepage function, the tunnel excavation process is simulated by considering the role of groundwater seepage, it is conclusion that the diversion tunnel surrounding rock stress and strain change rule.