Studies On Deterioration Mechanism Of A Subway Tunnel Structure Under The Environment Of Different Groundwater Levels

With the development of city, more and more subway been built in the city. As a part of urban traffic, subway has become more and more important to the urban traffic. When come to Beijing, where the subway develops quite quickly, the problems of tunnel structure receive more and more attention. The south-north water diversion project, which introducing the water from south to north, would change the distribution of Beijing groundwater, and the change of water environment could affect the tunnel structure. Research on the effects of Beijing groundwater to the tunnel structure has quite important meaning and forward-looking, and it also can guide to prevent the destruction of tunnel structure result in the change of groundwater.Theory and research on the fluid-structure coupling effect with the act of the groundwater environment change are not many more now, in this paper, according to theory of seepage and damage theory of knowledge, the stress and strain of tunnel structure under different groundwater level are studied both using analytical and numerical methods. Then using the modified damage model, it can clearly define the damage of tunnel when the groundwater level rose. The main original work includes:(1)Base on conventional method, analytical solution of tunnel structure under different level of water was derived; stress and strain of the structure were stimulated by using Flac3 D, which is the software contributing to underground engineering. Comparing the results of above, the model comfort to real situation was built.(2) According to the model built on the first step, it stimulates and analyses the effects on the tunnel structure under different groundwater levels by fluid calculation in Flac3 D.(3) Considering the permeability changes of tunnel structure and basing on the theory of damage, it can build the damage evolution equation and damage model of tunnel structure under different groundwater level, and then it can also modify the damage model by Fish language and analysis the damage of tunnel structure, which could quantitative the effect of groundwater to tunnel structure on some extend.(4) As the study show, the change of groundwater level has certain damage on the tunnel structure, and the damage is not to be ignored. On the other hand, the stress distribution under the change of groundwater would change, and have the additional stress. Differential settlement of the tunnel structure may cause the fracture of tunnel structure, which would contribute to the leakage of tunnel structure.