| Layered rock mass is one of the most widely distributed rock masses on the earth undefineds surface.The disaster of surrounding rock in the underground caverns of heavily buried layered rock mass has become one of the key problems restricting the safety of engineering construction,which is mainly reflected in the low bearing capacity of deep layered rock mass and the large-scale fracture of rock mass after being disturbed by excavation,and so on.Because the mineral composition of rock,the dip angle of bedding plane,the spacing and the stress state are very different,the deep buried layered rock mass shows different physical and mechanical properties.At present,it is not mature to study the deformation and failure law of underground caverns in deep layered rock mass,especially in meso.It is of great theoretical significance and practical value to study the deformation and fracture characteristics and mesoscopic evolution of deep layered rock tunnel.Based on the results of routine uniaxial and triaxial tests of chlorite schist in the northern end of the TBM section of the diversion tunnel of YinHanJiWei,this paper makes use of the discrete element numerical method and the theories of fracture mechanics,damage mechanics and so on.In this paper,the related characteristics of the stratigraphic surface of chlorite sheet are studied in detail.The main work of this paper is as follows:(1)Based on discrete element theory and Weibull distribution theory LPB model and SJ model a mesomechanical contact model of heterogeneous layered rock mass and its calculation method are presented.(2)Based on the analysis of SEM mineral composition test results of chlorite schist,a mesostructure model of layered rock mass based on mineral particles is established,and the mesomechanical parameters of chlorite schist are calibrated in combination with the identification method of rock mesomechanical parameters.The mesomechanical numerical model of layered rock mass is established.(3)Taking layered rock mass under different bedding plane inclination angle,different bedding plane spacing and different confining pressure as the research object,uniaxial digital model test and triaxial digital model test are carried out.The effect of stratified plane effect on the mechanical properties of layered rock mass is studied in depth.The deformation,fracture and mesoscopic evolution of layered rock mass are clarified.The results show that in uniaxial and triaxial tests,The curve of relationship between peak strength and plane inclination of rock mass is U-shaped,showing obviousdifference of dip angle,and the smaller the spacing of bedding plane,the lower the peak strength.(4)Based on the mesomechanical model of layered rock mass and related theories,the tunnel model is established,and the influence of different initial stress level,different side pressure coefficient,different bedding plane inclination and spacing on the stability of surrounding rock and the damage model of surrounding rock burst are analyzed.The larger the lateral pressure coefficient,the smaller the spacing of the bedding plane and the progressive increase of the initial stress,the greater the probability of surrounding rock failure after the excavation of the tunnel. |
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