非饱和土中热-湿-盐耦合作用的稳态分析

Steady-state analysis of the heat-moisture-salt coupling for unsaturated soil

以多孔介质理论为基础,研究了稳态条件下非饱和土中温度-水分-盐分多场耦合问题。考虑非饱和土的孔隙被液态水、溶解的盐分、水蒸气和干燥气体等填充,在质量和能量守恒的基础上获得了非饱和土中水分、气体、盐分的质量守恒方程以及能量守恒方程。考虑一维稳态问题,选取温度、孔隙气压、孔隙水压和盐溶液浓度以及它们的导数作为状态变量,得到了问题的状态方程组。在给定的边界条件下,采用打靶法求解了该强耦合的非线性变系数微分方程组,通过与已有的试验结果相比较,验证了模型的有效性。基于数值算例,参数分析了含水率、温度边界、孔隙率等条件对非饱和土中温度场、水分场和盐分场分布的影响规律。

The multi-field coupled heat-moisture-salt behavior of unsaturated soils under steady state is investigated using porous media theory.It considers that the pores are filled with liquid water,dissolved salts,water vapor,and dry gas.The mass conservation equations of moisture,gas,and salinity in unsaturated soils and the energy conservation equations are presented.Considering one-dimensional steady-state problems,the state equations are obtained by using the temperature,pore pressure,pore water pressure and salt solution concentration and their first-order derivatives as the state variables.Under given boundary conditions,the coupled nonlinear differential equations for the varying coefficients are solved by shooting method.The validity of the model is verified by comparing with the existing experimental results.Based on numerical examples,the influence of moisture content,temperature boundary and porosity on the distribution of temperature field,water field and salt field in unsaturated soils was discussed in detail.