Study On The Soil Metro Tunnels Dynamic Interactions In Ground Fissures Area

Since discovered in 1959, the ground fissures in Xi'an have caused serious damaged to the development of the city and daily life of the citizens. The ground fissures influensed the metro tunnel system of the city. There are totally 14 ground fissures in Xi'an; most of them have junctions with the 1st and 2nd line of the metro system. The activities of the ground fissures will have closely relationship with the safety of the metro tunnel system. The Xi'an is a city has potential of earthquake activities for its geology characteries, with the research from the history earthquake activities, when the life lines of the city as the metro system damaged by the earthquake activities, it was hard to recoverd and caused disters to the emergency system. It is a difficult research topic for building metro system in the ground fissures area, so lots of attentions paied in the research and engineering field.Based on the key work as the Xi'an metro system across the ground fissures, the dissertation focused on the soil and metro tunnel dynamic interactions in the ground fissures area. The field survey, the shakin gtable test & the FME method were used in the research for the dynamic characters of the ground fissures and the metro tunnels. The different metro tunnels as shield tunnel, the horse shoe shape tunnel were set up models in the shakeing table test and FME.Based on the ground fissures movements and its damaged to the underground structures, the shaking table model test of the ground fissures had set up. The result showed that the soil covered on the ground fissures would break and the fissure would be longth and wideth and there would have some small fissures near the original one. The close and open of the fissure in the dynamic activities caused a way to the soil which can lift from the bottom along the fissure.There were models of the shield tunnel and horse shoe shape tunnel for the shaking table. For the results of the shaking table tsets, conclusions as these wre got, the acceleration of the tunnel is bigger than the adjact soil; the dynamic soil pressure is serious to the tunnel in earthquake activities; the bottom of the tunnel has bigger stress than other parts of the tunnel.The shakin gtable test of the metro tunnel locates in the ground fissures area got that for the ununiform settlement in the south and north parts of the ground fissures, the stress of the tunnel close to the fissure were bigger than that far away the fissures. When the soft injunction used in the tunnel, the bigger stress decreased, and the differents parts of the tunnel move separately.The FEM model for the shield tunnel and horseshoe shape tunnel were set in the Marc, the study showed that the shear stress of the tunnel is bigger, for the design should consider the shear stress; the bottom of the tunnels have bigger dynamic acceleration and main stress. When the south part to the fissure was settle, there are friction, pressure and shear stress in the junction part of the tunnel.