Ground Deformation Prediction Of Expansive Soil Using Coupled Thermo-hydro-mechanical Theory

Analysis methods of deformation prediction of unsaturated soil are mainly empirical method,oedometer test method,suction method and numerical method.The numerical multiphysics coupling analysis method has many advantages such strong ability to deal with complex problems,and is widely used in the problem of complex analysis of multiphysics coupling in soil.In order to accurately analyze and predict the problem of uplift deformation of unsaturated expansive soil,this paper studies and establishes a set of partial differential equations and corresponding numerical models for solving the uplift deformation of unsaturated expansive soil based on the thermo-hydro-mechanical coupling theory method.Taking into account this,the following main research work was carried out.(1)Based on the theory of unsaturated soil mechanics,considering the coupling effect of matric suction,soil deformation and thermal convection,the partial differential mathematical equations of thermo-hydro-mechanical coupling analysis of unsaturated expansive soil are established.This set of equations can be utilized to analyze the stress and deformation of unsaturated expansive soil during expansion and drying under different environmental conditions such as water content and temperature.(2)In the multiphysics simulation software COMSOL Multiphysics,the partial differential mathematical equations of the thermo-hydro-mechanical coupling analysis of unsaturated expansive soil is realized by the finite element method.The measured data of soil deformations caused by wetting verified the correctness of the numerical model,and compared with the theoretical analysis results of hydro-mechanical coupling theory,theoretical analysis results of thermo-hydro-mechanical coupling theory are more accurate.(3)The effects of Poisson's ratio and temperature on the deformation of expansive soil with different boundary conditions are systematically analyzed.The changes of matric suction,deformation,strain and soil temperature are studied.The deformation,temperature and soil permeability of expansive soil are found.There is an important correlation between temperature changes,especially when the soil is in a colder zone.The lower the matrix suction,the larger the deformation of the expansive soil;the Poisson's ratio change affects the soil deformation,the Young modulus variation depends of the matric suction;the Poisson's ratio of the expansive soil was took between 0.3 and 0.4 during the pumping process,and the soil is prone to deformation for lower values.As the Young's modulus increases,the temperature drop will reduce the deformation of the soil.