Stability Analysis On Rive-crossing Shield Tunnel Of Nanchang Metro Line One

Usually in the excavation of a shield tunnel, due to the influence of different geological conditions and construction factors that will make the result is not ideal, when the research results of tunnel stability in a certain area applied to other areas of the problem, it is also very necessary to study the independent tunnel of the specific conditions of a particular region.In the construction process of the river-crossing tunnel which is a part of a city subway in Nanchang, due to the particularity of regional conditions and the study of Nanchang area subway tunnel is less, it makes the study of the stability of the Tunnel-Across-River in Nanchang city metro particularly important.This paper summarizes the research on the stability of tunnels from domestic and abroad. Using MIDAS GTS NX software to set up subway river-crossing tunnel 3D finite element model on the basis of Nanchang regional geological parameters.This paper discusses the different conditions of surrounding rock and lining under the influence of the changing rule of the stress and strain; it also studies the water level, buried depth of the tunnel and the influence of the related parameters about geological fault on the stability of the Tunnel-Across-River. We can make the following conclusions:(1)The tunnel surrounding rock stress field will release concentration stress around to the lining with construction completed. The stress will be bigger along with the rising of water level, the increasing buried depth of tunnel, and the decreasing distance of the faultage. But the increasing stress value is small, so it will not have much influence on the stability of the surrounding rock.(2)The surrounding rock and lining both point to deformation of the tunnel center with which Characterized by the settlement of the earth's surface and arch, the lining of the bottom uplifting, the deformation increases as the increasing of water level and tunnel buried depth. It also decreases with the decreasing of the distance and faultage. When the tunnel buried depth is more than 2 times of the tunnel diameter, the change of the parameters on the surface displacement has no obvious influence.(3)The lining of principal stress increases with the rising of water level and the increasing of tunnel buried depth slightly. But the lining of principal stress can produce changes in tunnel near the faultage zone. It changes suddenly at the intersection of faultage with the tunnel vault, arch waist and arch bottom. Mutations tend to make the stress value of tunnel lining a lot higher than the non-fault region. So it needs to focus on the faultage segment lining and to do the real-time monitoring.