| Due to the presence of structural surface, layered rock has poor continuity and remarkable anisotropy. Built in such rock, tunnel rock deformation and the form of destruction are relatively complicated and over-excavation problem is serious. In allusion to the characteristics of layered rock, on the background of Xishan tunnel project, on the basis of research and analysis of historical information and research, this paper studies on the influencing factors and failure mechanism of Horizontal Rock area tunnel surrounding rock instability.Firstly, with the research of stress field layered surrounding rock after excavation, this passage summarized the main factors affecting the stress distribution, including in-situ stress and rock mechanical properties, rock mass structure and structural geology and man-made factors. In addition, in-depth study of two main factors, ground stress conditions, the cross-sectional shape, using mechanical methods this paper gets tunnel stress field distribution of common shape section under general rock mass conditions and obtains tunnel excavation surrounding rock stress field distribution by numerical means containing structural surface rock mass that is the level of surrounding rock under.Secondly, regarding the surrounding rock each layer as isotropic continuous medium and considering the impact of the level, this paper proposes the distinguishing rule and destruction mechanism of layered surrounding rock stability. Considering the characteristics of surrounding rock in the deeply buried layered rock, RFPA2D finite element numerical software for tunnel construction process simulation to reproduce. Comparative analysis of the effect of cavern shape and spatial arrangement of structural surface on the stability of surrounding rock, this paper gets the instability damage process, stress, strain and acoustic emission distribution during tunnel excavation, all of which are of the surrounding rock. The numerical model experiments study the variation of the surrounding rock stress and failure characteristics and the results of the numerical analysis is basically the same to the theoretical analysis, which provide a reliable scientific basis for the similar engineering design and construction.Then, focusing on the research of stress field and instability mechanism, this paper also analyses the supporting system and mechanism of layered rock formations. Considering the surrounding rock tunnel excavation-supporting the mechanical behavior, this paper summarizes mechanical characteristics and application conditions of main support forms.At last, specific to Xishan tunnel construction which is typical horizontal rock, the theme uses the MIDAS software that is more specific and more targeted to simulate and analyze, and compares with the experimental parameters which are received in the construction site. Determine the rock support parameters and monitoring measurement focus and judge the rationality and security of the initial support structure. |
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