Study On The Analysis Method Of The Inhomogeneous Meso Fracture Of Layered Rock Mass And Its Application In The Tunnel

The rock mass actually entrusted to the crust mostly contains primary or secondary structural planes.Layered rock mass is a typical one.Its deformation and strength not only depend on its environment,but also on its own structural characteristics.It shows discontinuous,anisotropic and highly inhomogeneous characteristics on the macro level.With the development of geotechnical engineering in China towards large,high and deep burial,the typical characteristics of layered rock mass in high geostress environment bring tremendous risks and challenges to deep rock mass engineering.The existence of structural plane not only destroys the integrity of rock mass,but also directly affects the stability and long-term safety of deep underground engineering.Therefore,it is of great theoretical and practical significance to study the mechanical characteristics and failure mechanism of layered rock mass.In this paper,starting from the discontinuity,anisotropy and highly inhomogeneity of layered rock mass,the particle discrete element method based on discontinuous medium theory is used to explicitly consider the influence of layered rock mass layers.When establishing mechanical or computational models,different homogeneity of bedrock and layered joints are considered.The main research work of this paper is as follows:(1)Based on particle discrete element theory,different micro-contact models are selected to simulate bedrock and bedding joints of layered rock mass.By introducing WLPB model describing inhomogeneous cementation characteristics of bedrock micro-particles,WLPB model is used to characterize inhomogeneous cementation characteristics and mechanical response of bedrock micro-particles in layered rock mass.WSJ model describing meso-inhomogeneous cementation characteristics of bedrock joints is constructed.It is used to characterize the micro-inhomogeneous bonding characteristics and mechanical response of joints in layered rock mass.Combining WLPB model with WSJ model to consider the inhomogeneity of bedrock and bedding joint respectively,a new theory and calculation analysis method of inhomogeneous micro-contact mechanics model for bedded rock mass is put forward,and on this basis,a calculation program of micro-mechanics analysis for 2-dimensional inhomogeneous layered rock mass is developed.(2)Based on the inhomogeneous micro-mechanical calculation model of 2-D layered rock mass and the particle discrete element micro-numerical simulation method,the numerical calculation model of layered rock sample is established,and the customary mechanical parameters used in the calculation model are calibrated on the basis of indoor uniaxial compression test.The micro-mechanical numerical test under uniaxial compression is carried out with homogeneity,spacing and inclination of layers as influencing factors,and the deformation and fracture characteristics and micro-evolution law of layered rock mass under uniaxial compression are obtained.Furthermore,numerical calculation models of triaxial compressed layered rock mass under different confining pressures are established,effects of inhomogeneous layers under triaxial compression are analyzed,and special properties of layered rock mass,especially mechanical response of anisotropy and inhomogeneity under confining pressure,are explored.(3)Taking the diversion tunnel of Hanji-Weiwei River as the engineering background and using two-dimensional inhomogeneous micro-mechanics calculation model of layered rock mass,a tunnel model of deep-buried inhomogeneous layered rock mass is established,in order to reasonably predict the mechanical response of layered surrounding rock after tunnel excavation,and to study the regularity of deformation and destruction of tunnel surrounding rock,taking homogeneity of different layers,hydrostatic pressure,lateral pressure coefficient,dip angle of layers and layers as examples.The tunnel excavation simulation scheme is designed based on spacing and other factors.The deformation and fracture damage modes of tunnel surrounding rock under different influencing factors are compared and analyzed from the displacement field,microcrack distribution,failure mode and contact force chain of the model.