Development Of Thermal-hydro-mechanical Coupling Program For Unsaturated Soil And Its Application In Slope Deformation Evolution And Stability Analysis

The deformation of soil in nature is not only determined by the loading conditions(stress state and stress history),but also closely related to the natural environment(such as rainfall evaporation,temperature difference between day and night),which is essentially the result of the coupling of temperature field,seepage field and stress field.In the construction of deep energy engineering,underground disposal of high-level nuclear waste,excavation of underground space,construction of landfill,construction of urban buried heat pipeline and construction of high-speed railway subgrade in permafrost regions,the problems of soil deformation,seepage,heat conduction and water vapor migration under the influence of thermal-hydro-mechanical coupling become more and more prominent,The study of thermal-hydro-mechanical coupling characteristics of unsaturated soil has become a hot topic in the field of unsaturated soil mechanics.In order to provide theoretical basis and analysis method for geotechnical engineering problems under the influence of thermal-hydro-mechanical coupling,this paper studies the thermal-hydro-mechanical coupling numerical model of unsaturated soil and its numerical implementation,and simulates the relevant engineering cases involving thermal-hydro-mechanical three field coupling problems(1)The thermal-hydro-mechanical coupling mathematical model of unsaturated soil is established,and the Euler backward integration algorithm is derived,which improves the C language thermal-hydro-mechanical coupling calculation program independently developed by the research group.Firstly,based on the constitutive model established by Cai Guoqing,which is suitable for unsaturated soil under non-isothermal condition,considering the coupling of capillary effect and elastic-plastic deformation,a fully implicit Euler backward integration algorithm and uniform tangent modulus are derived;Secondly,by introducing the static equilibrium equation of mixture,mass conservation equation and energy conservation equation of liquid and gas phase,the thermal-hydro-mechanical coupling mathematical model of unsaturated soil is established,and the finite element calculation format of control equation is given;Finally,the Euler backward integration algorithm is embedded into the C language thermal-hydro-mechanical coupling calculation program,which is independently developed by the research group.(2)The improved thermal-hydro-mechanical coupled finite element program is used to simulate the triaxial shear behavior of unsaturated soil under different test conditions(temperature,confining pressure and suction),which verifies the rationality and effectiveness of the program.A three-dimensional finite element numerical model is established to simulate the triaxial shear behavior of unsaturated soil under different temperature,confining pressure and suction.By comparing the results of numerical simulation including shear strain deviatoric stress / volume strain curves with the experimental results,the rationality and effectiveness of the program are verified.(3)Using the improved thermal-hydro-mechanical coupling finite element calculation program,the model test of slope seepage instability is simulated,and the rationality and effectiveness of the program are verified again.The finite element model of slope is established by using the improved thermal-hydro-mechanical coupling calculation program to simulate the model test of slope seepage instability.This paper mainly simulates the evolution process of seepage field and deformation field of slope under top seepage,compares and analyzes the simulation and test results of pore water pressure change curve at monitoring points,and explains the reasons of pore water pressure change in detail,which verifies the rationality and effectiveness of the program again.(4)The improved thermal-hydro-mechanical coupled finite element program is applied to the simulation of slope engineering,focusing on the influence of model parameters on the simulation results of slope deformation field.The deformation field,seepage field and temperature field of unsaturated soil slope under the condition of thermal-hydro-mechanical coupling are studied by using the finite element program of thermal-hydro-mechanical coupled multiphase flow developed by C language.The effects of saturated plastic compression index,saturated elastic compression index,critical state line slope rate,rainfall intensity,slope height and slope on the deformation field of slope are deeply studied,the results show that the slope of the critical state line has the greatest influence on the deformation of the slope before instability,and the rainfall intensity has the greatest influence on the stability of the slope.(5)The improved thermal-hydro-mechanical coupling finite element calculation program is applied to the simulation of slope stability under thermal-hydro-mechanical coupling condition.Based on the perfect thermal-hydro-mechanical coupling finite element calculation program,the stability of slope under thermal-hydro-mechanical coupling condition is studied by using the method of increasing weight.The variation trend of safety factor of slope under three working conditions of considering only stress field,considering stress field,seepage field and considering stress field seepage field temperature field is analyzed,the variation law of slope safety factor under different rainfall intensity is studied.