Study On Security And Stability Of Deep Buried Highway Tunnel Based On Anisotropic Theory

Funded by"Research on Stability and Reliability of Tunnel and Underground Space Structure", a key project of National Nature Science Foundation of China, and taken GongHe tunnel(which was located between the villages and towns of Wulong and Pengshui, one segment of interprovincial highway from Chongqing municipality to Changsha metropolis) as an engineering example, in this paper tunnel in-situ-stress was tested and simulated firstly. Then, the failure mechanism of surrounding rock in deep buried tunnel was discussed using constitutive model of transversely isotropic and plastic. And meanwhile, rock burst, a familiar brittle fracture of hard rock in deep-buried tunnel, was forecasted by using BP neural network. For the research, the main studying content is listed as follows.Geostress is a indispensable precondition to ascertain the mechanical property of rock body, analyze the stability of surrounding rock, design the excavation of tunnel engineering and make decision scientifically. In this paper, for the reason of the lack of experimental information in a large scale, the technique of stress relief was applied to measure the geostress in the test tunnel segment of GongHe tunnel. The caky phenomenon of rock sample was also simulated by numerical method.Using the formula of stress distribution, strain distribution and distance distribution of bore wall educed by anisotropic theory, the geostress of tunnel zone was analyzed according to the geostress measure data, and the result indicated that the geostress was affected obviously by the chosen constitutive model, that is, different constitutive model leads to different results. So, it is very important to choose the proper constitutive model to rest with the geological condition of the actual engineering.The constitutive model of transversely isotropic and plastic was established based on the rock characteristic of transversely isotropic and the yield property under high stress condition. Also, the constitutive model was programmed using C++ computer language, then the program was embedded into the software of FLAC3D. The validity of program in transversely isotropic and plastic was tested separately by a general example, which can be used in the analysis of correlative issue.The failure of surrounding rock support for GongHe tunnel was studied using transversely isotropic and plastic constitutive model by numerical analysis method. According to the numeration result, design optimization of surrounding rock support was analyzed, and the result showed that the failure zone was dissymmetrical seriously. So, the weakness zone should be strengthened by bolting and shotcrete supporting. Based on the theory and method of artificial neural network, the prediction of possibility of rockburst for GongHe tunnel was studied during the course of tunnel excavation. Furthermore, the prediction difference of rockburst was discussed whether the rock characteristic of transversely isotropic was taken into account or not.