Peridynamic Numerical Simulation Of Thermo-Hydro-Mechanical Coupled Problems In Crack-Weakened Rock

With the continuous development of national economic construction,there are many multi-field coupling problems involved in more and more rock engineerings.The Thermo-Hydro-Mechanical coupled problems in fracture rock become a hot research topic and research challenges.Because of the complexity of the multi-field coupling geological environment in practice project and the limitations of laboratory test,numerical simulation method is still one of the most effective approach to study the multi-field coupling problems in fracture rock.Peridynamic theory is in the category of nonlocal theory,it can effectively avoid the singularity of stress field at the top of cracks by using spatial intergral equtionsrather than spatial derivative to describe the mechanical behavior of materials.Therefore,it is highly appropriate to solve discontinuous problems.Since the peridynamic theory is based on nonlocal theory,it can be applied to simulate heat transfer and seepage problems.In this thesis,the Thermo-Hydro-Mechanical coupling model of fracture rock is established based on peridynamic theory,and the numerical calculation procedure has been programed to verify the Thermo-Hydro-Mechanical coupling model.The main work of this paper are as follows:(1)The shear deformation is taken into account in bond-based peridynamic by introducing an extra parameter,shear stiffness.The introduction of the extra parameter improved the constitutive relation of bond-based peridynamic theory form microscopic mechanism,and the relationship between peridynamic microscopic mechanical parameters and macroscopic elastic constant are obtained.Base on the peridynamic Cauchy stress tensor,a non-ordinary state-based peridynamic damage model is established.The stress on bond is derived by the stress on particle,and the maximal tension stress strength theory and the twin shear strength theory are used to determine if the bond is break.The damage of a particle is determined by calculating the percentage of the broken bonds form total bonds of the particle.The damagae model was used to simulate the initiation,propagation and coalescence of rock cracks under uniaxial compressive loads,and the stress-strain curves are obtained.(2)Peridynamic thermal diffusion theory is derived by using Euler-Lagrange equation.The relationship between peridynamic microscopic thermal conductivity and macroscopic thermal conductivity are determined.According to the thermal expansion property of materials,the deformation gradient is derived from the temperature field which is calculated by using peridynamic thermal diffusion equation.Then,the Thermo-Mechanical coupling model based on peridynamic is established.(3)According to Darcy's law,a nonlocal peridynamic seepage equation is derived.The relationship between peridynamic micro-hydraulic conductivity and macroscopic hydraulic conductivity are obtained.On the basis of the Biot fluid-solid coupling theory of porous media,the influence of the pore water pressure is introduced to the non-ordinary state-based peridynamic constitutive equation and the impact of the effective stress on hydraulic conductivity is introduced to the peridynamic filtration equation.Then,Hydro-Mechanical coupling model based on peridynamic is established.(4)Base on the peridynamic thermal diffusion theory and the peridynamic seepage theory,the Thermo-Hydro coupling model mathematical formulae are derived.Finally,on the basis of the two-field coupling of temperature field,seepage field and stress field,the Thermo-Hydro-Mechanical coupling model of fracture rock is established.The multi-field coupling model is applied to simulate the failure process in the surrounding rock of deep roadways,and discusses its application prospect.