| Various complex geological situations and environmental factors will be encountered in the construction of major infrastructure such as transportation and energy.The fractured rock mass plays a very important role in guaranteeing the safety and stability of the structure.A large number of natural defects have sprouted in the formation process of rock mass over a long period of time,and its deformation,damage and failure law will be affected by the surrounding physical field and strength.The problems of structural instability caused by the cracking,expansion,connection and penetration in fractured rock mass under external load have always been the focus of scholars.Numerical simulation methods are widely used in rock mass mechanics analysis with high efficiency and low cost.The peridynamic method can effectively avoid the tip singularity problem,and can simulate the spontaneous failure process of crack without setting the propagation path.The method has great advantages in handling with discontinuous issues such as fractured rock mass.This paper is based on the research on the damage and seepage characteristics of fractured rock mass in the field of transportation infrastructure construction and energy mining.The peridynamic theoretical model suitable for describing the mechanical characteristics of fractured rock mass is gradually established.The contents are as follows:(1)There are disadvantages of large boundary error and fixed Poisson’s ratio when simulating material deformation in the classical bond-based peridynamics.The deformation assumption is used to establish the relationship between the micro modulus and the elastic constant in continuum mechanics.The indefinite equations are constructed by stiffness equivalence,and the least square minimum norm method is used to solve the optimal micro modulus The kernel function which could reflect the degree of nonlocal action is introduced to improve the calculation accuracy.The deformation and crack propagation process of brittle materials are simulated,and the numerical convergence and applicability are analyzed.(2)The bond-based peridynamic method with integral governing equation does not involve the concept of stress and strain,and there are applicability and analysis limitations in simulating material damage and failure.Nonlocal differential operator in the form of numerical integration is introduced to calculate the stress value at the dissociation point.The peridynamic stress-strain analysis model is established,the deformation and failure of rock materials are simulated to verify the effectiveness of the method,and the influence laws of particle discrete spacing,Taylor term and weight function are analyzed(3)The critical energy release rate criterion in the classical theory does not consider the changes of micromechanical parameters at the damage,and can not distinguish the tensile and shear failure of rock materials.Based on the strain energy density criterion of strain softening,the mechanical index at the peridynamic crack tip is connected with the residual strain energy.At the same time,the tensile strength and Mohr Coulomb criterion are used to judge the failure of the bond,and peridynamic damage model based on the tensil-shear failure criterion is established to simulate the fracture process of rock materials under compressive load.(4)In the peridynamic seepage diffusion theory,the nonlocal action relationship and the heterogeneous seepage when simulating the macro fracture and matrix of rock are not fully considered.Based on peridynamic seepage diffusion model,the high-precision convergent kernel function is introduced and the corresponding permeability coefficients are deduced.According to the seepage characteristics of rock matrix and macro fracture,the peridynamic model of non-uniform seepage in fractured rock mass is proposed,and the peridynamic full coupling analysis method of damage seepage in fractured rock mass considering the interaction between mechanical field and seepage field is further established.(5)The investigation on the mechanism of equal interval fracture and the law of crack distribution in layered rock mass is carried out.The strip and network interval fracture process of the interlayer and surface in layered rock mass under boundary load is simulated,and the effects of loading ratio,thickness and other factors on the results are analyzed.A peridynamic fluid-solid coupling algorithm for instability and seepage failure of surrounding rock under excavation disturbance is established.Deformation and seepage failure process of surrounding rock mass during excavation in tunnel are simulated,which is compared with with model test to verify the effectiveness of the method.The mechanism of instability and seepage failure of water rich surrounding rock induced by excavation disturbance is revealed. |
