Peridynamics Simulation Analysis Method Of Water Inrush Due To Rock Mass Failure Under Tunnel Excavation

Water inrush has seriously restricted the construction of tunnels and underground projects in China to move forward with higher quality and efficiency,and has become an obstacle to the realization of the strategic goal of a powerful transportation country.It is the theoretical basis for solving the problem of safety prevention and control of tunnel construction to deeply understand the evolution process and mechanism of water inrush.In recent years,with the rapid development of computer technology and the wide application of numerical analysis methods,using numerical simulation to solve engineering construction problems,reproduce the evolution process of geological disasters,and reveal the evolution law of key information in the process of disasters has gradually become a research hotspot,which also provides a solution for the scientific understanding of the evolution process of water inrush in tunnels.In this paper,the peridynamics simulation analysis method of water inrush due to rock mass failure under tunnel excavation is the main research objectives.Aiming at the gradual failure process of water inrush caused by the combined action of tunnel excavation unloading and groundwater seepage,the peridynamic method based on the thought of non-local action is used.And the theoretical analysis,mathematical derivation,program development,numerical example verification and engineering application are combined.By combining the advantages of peridynamics in simulating the continuous and discontinuous deformation and damage of solid materials and groundwater seepage,a peridynamics simulation method is established to describe the fluid-solid coupling failure process of fractured rock mass driven by fluid pressure.And the material point dormancy method and three-dimensional matrix operation method are proposed to describe the unloading effect of tunnel excavation.Therefore,the stress-seepage peridynamics simulation analysis method considing the unloading effect is established.Finally,it is successfully applied to simulate the water inrush disaster process of typical karst tunnel,revealing the influence law of different influencing factors on the water inrush disaster process due to the failure of rock mass,and providing an important research means for the prediction,early warning and safety prevention and control of related geological disasters.(1)The rock mass is usually composed of rock blocks cut by discontinuous structural planes such as joints and fissures,and has obvious discontinuous deformation characteristics.To describe the strength weakening effect of joints and fissures,a strength reduction constitutive model of jointed and fractured rock mass is established by introducing the strength reduction coefficient.The short-range repulsive force reflecting the incompressibility of material points and the Weibull distribution function reflecting the heterogeneity of rock material are introduced into the basic governing equation And an efficient solution method and program for three-dimensional peridynamics based on matrix operation is independently developed.Thus,the effective simulation of peridynamics in the process of compressive failure of jointed and fractured rock mass is realized(2)The fluid-solid coupling failure mechanism of fractured rock mass is the key to simulate the disaster evolution process of tunnel water inrush with rock mass failure.Based on the idea of nonlocal action of peridynamics,the equivalent continuum model,the discrete fracture network model and the pore-fissure dual medium model are established to simulate groundwater seepage.Combined with the principle of effective stress,a material point double repeated cover theory model is proposed to reflect the coupling effect of solid material deformation and failure and groundwater seepage.A peridynamics fluid-solid coupling simulation method is established to simulate the hydraulic fracturing process of fractured rock mass,and the coupling mechanism of stress-seepage-damage in the hydraulic fracturing process of fractured rock mass is revealed.(3)Excavation unloading is the main reason to induce tunnel surrounding rock damage and water inrush.At present,peidynamics method has not been widely used in the field of geotechnical engineering,and there is a lack of theory and method to describe the process of surrounding rock unloading.The material point dormancy method is proposed to simulate the unloading effect of tunnel excavation.By comparing with the field observation data and previous research results,the validity and reliability of this method in simulating the evolution law of tunnel excavation damage zone are verified.Furthermore,the stress-seepage peridynamics simulation method considing the unloading effect of is established.Which realizes the effective prediction of the distribution and morphology of the excavation damage zone during tunnel construction in jointed stratum under the coupling effect of stress-seepage,and provids an effective numerical method for the disaster simulation of rock mass failure and water inrush during tunnel construction.(4)Tunnel water inrush with rock mass failure is a typical continuous-discontinuous dynamic variation process under the comprehensive action of adverse geological structure and underground engineering activities,which puts forward higher requirements for the establishment and solution of numerical model.By using the self-developed simulation method and program of stress-seepage peridynamics considing the unloading effect based on matrix operation,the simulation of the whole process of the contact,fusion and penetration between the excavation damage zone and seepage damage zone and the formation of water inrush channel in karst tunnel construction process at the scale of model test is realized.Which is based on the typical karst cave water inrush case of Xiema Tunnel,and under the comprehensive action of excavation unloading and groundwater seepage.(5)The mechanism of karst tunnel water inrush disaster is very complex.Correct understanding of the occurrence conditions and influence rules of water inrush disaster is the basis of water inrush disaster prevention and control.Relying on the engineering background of Xiema Tunnel,the engineering scale karst tunnel water inrush disaster process simulation is carried out.By comparing and analyzing the progressive failure of rock mass and the formation process of water inrush channel under different influencing factors,such as the development scale of karst cave,karst cave water pressure,surrounding rock material properties and tunnel depth,the influence mechanism of these factors on the disaster process of water inrush is revealed.Through the analysis of the minimum safe thickness of the structure and the water inrush prevention and control measures,it provides scientific guidance for the prediction,early warning and safety prevention and control of water inrush disasters in karst tunnels.(6)Peridynamics has great application potential in the field of geotechnical engineering due to its unique advantage in simulating material damage and failure.However,there is no mature numerical simulation software for popularization and application.Based on independent research and development of the simulation method and procedures of stress-seepage peridynamics considing the unloading effect,using C++ and Matlab mixed programming technology,the numerical simulation software with independent intellectual property rights of friendly interface,convenient operation and strong extensibility is developed.The numerical simulation software is especially suitable for geotechnical engineering problems,and is named as Peridynamics Engineering Simulation Laboratory(PESL).It provies reference for the application of peridynamics in geotechnical engineering and other fields.