| The construction scale of tunnels and underground projects in China is huge and the construction conditions are complex.Many tunnels are built in the complex stratum environment with-water rich,high water pressure and karst,and many geological disasters occur frequently.In a wide range of engineering needs,numerical simulation has become one of the most important means to study the disaster mechanism and evolution process of underground engineering.Peridynamics is one of the most advanced numerical methods for solving discontinuous problems,especially for simulating continuous discontinuous problems.This paper is based on the numerical simulation analysis of the disaster evolution process caused by the fluid-solid coupling of the fractured rock mass.Through theoretical derivation,numerical simulation and other means,the basic problems of the fluid-solid coupling of fractured rock mass in the peridynamics are studied,and a series of beneficial research results are obtained.Firstly,in the peridynamics scale,by considering the plastic deformation of the bond between the material points,the response of the bond to different stress states(loading and unloading)is improved.Considering the influence of post-peak loading and unloading path on the mechanical behavior of rock,a micro elastic-plastic constitutive model is proposed;The non-uniform discrete modeling method is used to characterize the non-uniform characteristics of rock mass materials,which solves the "discrete structure dependence" in the process of material simulation compression failure,and improves the accuracy of numerical simulation.The applicability and accuracy of the micro elastoplastic constitutive model are verified by uniaxial compression and cyclic loading-unloading tests.At the same time,the failure process simulation of standard rock specimens under uniaxial compression test with different fracture dip angles is carried out,and the simulation results are in good agreement with the experimental phenomena.Secondly,based on the basic theory of ordinary state-based peridynamics,the basic equations of ordinary state-based peridynamics for plane stress and plane strain problems are familiar with and derived from the perspective of strain energy density.Based on this theory,Drucker Prager criterion(DP)is used to construct the plastic yield surface of rock material in the form of ordinary state-based peridynamics,and the incremental form of ordinary state-based peridynamics micro elastic-plastic constitutive equation is obtained;In order to improve the calculation efficiency,the coupling simulation analysis method of ordinary state-based peridynamics and finite volume method is further studied,and the numerical calculation method to solve the fluid-structure coupling problem of fractured rock mass is proposed.The displacement field,equivalent force field and fracture propagation process are solved by using ordinary state-based peridynamics.The seepage field of fracture is solved by the finite volume method,and the fluid-structure coupling is realized by data exchange.Several numerical examples are given to verify the ability of the method to simulate crack propagation in fluid-driven saturated fracture-porous media.Finally,the distribution and migration of groundwater in the spring area are studied,and the equivalent pore medium model and pore fracture dual-medium model are set up.Ten groups of working conditions are simulated respectively for the influence of tunnel excavation on different groundwater levels under the same tunnel depth and the influence of tunnel excavation on groundwater levels under the same water level.It is concluded that the fracture development of rock mass plays a leading role in the damage of surrounding rock during tunnel excavation,and when the pore water pressure exceeds a certain value,the fracture development and pore water pressure will become the leading factors of the damage of surrounding rock during tunnel excavation.It provides effective theoretical support for rail transit route design and tunnel engineering safety construction. |
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