Elastoplastic Analysis of Coupling Mechanism for River-crossing Tunnel under Seepage Condition

Recently, the water environment, especially the investigation on the influence mechanism of high water pressure or water seepage on the tunnel stability is not thorough. In this study, based on the theory of seepage mechanics and elastic-plastic theory, the stress state of tunnel rock mass under the coupling of seepage field and stress field is analyzed, the formula for calculating the radius of plastic zone, the stress and displacement of the rock mass in the elastic-plastic state are derived. The stress and displacement of tunnel surrounding rock and the mechanical characteristics of the supporting structure are analyzed under the condition of seepage. Introduction With the rapid development of underground engineering, groundwater is almost always accompanied by underground engineering, groundwater preventing problem has plagued engineering field. Underground work in the confined water, groundwater control is more complex, the problem becomes more and more prominent. In recent years, our country built a large number of mountain tunnel, cross river tunnel, mine tunnel and all kinds of underground engineering, the tunnel will be excavated with complex geological environment. These tunnels have most of the groundwater with a certain pressure. In order to ensure the construction safety of tunnel, the tunnel construction encountered in the process of high pressure groundwater must be controlled and grooming. For the water hydraulic tunnel, tunnel lining structure is subjected to the hydrodynamic pressure load inside tunnel and water pressure outside tunnel liner. For the non-hydraulic pressure tunnel, water pressure does not exist, there is only the external water pressure. Because the sealing impervious tunnel liner is not absolute, so the effect of water pressure on tunnel liner is the liner surface force and liner seepage volume force. Because the tunnel liner and the rock mass are permeable media, it can be considered that the movement of water seepage between the liner and the rock mass is continuous. In many cases, the tunnel liner and rock mass is not completely closed, there are pores, due to the existence of pores in the volume force of tunnel rock mass will not be directly transferred to the tunnel liner, this part becomes an independent structure to withstand water pressure. At present, the water environment, especially the investigation on the influence mechanism of high water pressure or water seepage on the tunnel stability is not thorough. The high pressure tunnel with complicated hydrogeological conditions or river tunnel construction under the influence of seepage field and stress field coupling model is not perfect, which cannot fully reflect the seepage field and the stress field in the high pressure. In this paper, based on the coupling theory of seepage field and stress field, the interaction between rock mass and tunnel liner was analyzed. The research results can provide important guidance for underwater tunnels and mountain tunnels. Model Establishment In this study, the circular tunnel is taken as the research object. The following assumptions are considered in this model: tunnel diameter is a, the pore water pressure of the tunnel wall is P1, the vertical distance from the tunnel center to the riverbed is b, and the far-field water pressure is P0. It is assumed that the initial stress of rock mass is the self-weight stress, the lateral pressure 5th International Conference on Machinery, Materials and Computing Technology (ICMMCT 2017) Copyright © 2017, the Authors. Published by Atlantis Press. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/). Advances in Engineering, volume 126