| The study of multi-field coupling characteristics of thermohydromechanical and contaminant migration in porous media is an urgent problem that needs to be solved in environmental geotechnical engineering.It has important research significance in evaluating and predicting the impact of various projects on the environment.Based on the relevant research domestic and foreign,this study derives the basic control equation of the multi field problem of thermo-hydro-mechanical-migration.And the feasibility and correctness of the control equation are verified by comparing with the existing research results.The dynamic coupling response characteristics of temperature and moisture content in the process of heating and cooling of clay under different initial saturation conditions are studied by using the designed multi field coupling laboratory test device.The main research content includes:(1)A non-equilibrium adsorption theoretical model is proposed for the problem of contaminant migration,based on the physical meaning of the Freundlich linear isothermal adsorption model.The adsorption degree of pollutant transport is evaluated effectively according to the accumulative mass fraction and relative concentration.Secondly,the discretization method is used to approximate the non-steady state of the seepage velocity and pollutant concentration with time as a steady-state problem within a short time.Then the steady state solution is used to obtain the unsteady state for equilibrium adsorption.The approximate solution of the problem of contaminant transport in the situation,and the derivation of the approximate solution of the non-equilibrium adsorption problem in the unsteady state.Finally,a theoretical model describing the nonlinear adsorption and desorption in contaminant transport was proposed according to the above model.Based on the suspended particle penetrating soil column test,the experimental data were fitted.(2)The T-H-M coupling equations of force and the corresponding state equations are given in this paper,based on the relationship between saturation,pore water pressure and pore gas pressure in the commonly used soil-water characteristic curve VG model,and the theory of thermodynamics,thermoelasticity,and unsaturated porous media seepage.And compared with the existing research results,the feasibility and correctness of the research have been verified.Based on the control equations of the thermo-hydro-mechanical three-field coupling action in the unsaturated case,the coupled equations of the saturation condition are obtained.The modulus of elasticity is corrected and its expression is given,considering the influence of temperature and pore water pressure on the elastic modulus of drainage.In addition,the existing thermal consolidation test was used to verify the feasibility and correctness of the abovetheoretical model.The evolution characteristics of pore water pressure,mean body strain and body strain in different consolidation processes are discussed.(3)On the other hand,the effect of dfferent initial saturations on the coupling response of seepage field,temperature field,and displacement field under thermal driving is further analyzed for the phenomenon that the saturation depth varies along the depth of the soil,and the influence process is simply expounded.The dynamic response characteristics of the temperature field and the seepage field in the process of heating and cooling under different initial saturation conditions are studied by the laboratory test.The experimental data are fitted by the above theoretical model.Numerical analysis of the distribution and variation of temperature field,stress field,pore water pressure field and nuclide concentration in near-field surrounding rock under the effect of water heat treatment in numerical repository is carried out.In addition,the coupled response characteristics of heat-water-force and contaminant transport were analyzed for different initial saturation of the buffer layer and different heat release strengths of the cured body. |
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