Research On Construction Mechanics And Spatial Effect Of Mijiazai Tunnel

With the implementation of the western development strategy, and the rapid development in highway transportation, the construction of mountain road tunnel in the western is presenting a brilliant situation. Among these many types of tunnel, the shallow unsymmetrical loading tunnel usually must be chosen for the need of the geological conditions, topography, lines, and cost control, etc.This paper combines a shallow unsymmetrical loading tunnel in Shanxi Province, and takes it as the project background. Through the elastic-plastic finite element numerical simulation method, the paper studies and explores the geological hazards during tunnel construction of this type of tunnel, rock pressure distribution in surrounding rock, construction mechanics and its influencing factors, the space restraint effort to the tunnel face, the interaction between adjacent tunnel during excavation period. The research of this paper is as follows:(1) Understand and summarize the relevant theory on the structure system of underground works, and get further understanding the mechanics principle of the New Austrian Tunneling Method in the interaction of the surrounding rock and supporting structure;(2) This paper summarizes the calculation methods of the surrounding rock pressure for shallow unsymmetrical loading tunnel; In combination with a shallow unsymmetrical loading tunnel in Shanxi Province, this paper lists and analyzes the geological hazards during construction;(3) In this paper, a series of two-dimensional elastic-plastic numerical model is created to do analysis on construction mechanics and its variation law under changing overlying rock-mass and soil-body thickness, different surface slope and construction methods, with the help of necessary calculation;(4) In this paper, a three-dimensional elastic-plastic numerical model is built, based on which calculation and analysis on construction mechanics of the shallow unsymmetrical loading tunnel, represented by Mijiazhai tunnel, is done. Then, stress is laid on the space restraint effort to the tunnel face, and exploring the deformation law along tunnel axis, feasible tunnel excavation pace, and the proper distance between adjacent tunnel faces; (5) Finally, combined with the result of numerical analysis, associated tunnel theory, and practical engineering experiences, this paper puts forward some suggestions on relevant construction steps of this kind of tunnel.