饱和土体热-水-力-化全耦合一维溶质运移模型

One-dimensional transport model for solute with thermo-hydro-mechanical-chemical soupling in saturated soil

基于孔隙流体质量守恒、能量守恒和溶质质量守恒,综合考虑力学固结、热固结与化学渗透固结对土体结构的影响,并结合黏土颗粒对溶质吸附、半透膜效应作用及耦合流、耦合扩散效应,建立了单一溶质在饱和土体中运移的热-水-力-化全耦合分析模型,采用COMSOL软件重点模拟了渗滤液环境温度对溶质运移行为的影响.数值结果表明,温度会显著影响溶质浓度随时空的分布,热扩散作用加速溶质运移进程,热渗透与热固结机制对溶质运移具有阻滞作用,模拟时间为50年时黏土垫层上下边界温差70 K比无温差工况溶质运移深度减缓87.6%.所建全耦合模型能够为填埋场防渗隔污屏障优化设计及服役性能评估提供理论参考.

A transport model with thermo-hydro-mechanical-chemical coupling in single solute in saturated soil was proposed,based on the principle of mass conservation of pore fluid,energy conservation and mass conservation of solute considering the influences of mechanical consolidation,heat consolidation and chemical-osmosis consolidation on the soil structure together.Meanwhile,the adsorption of clay particles,semi-membrane behavior,coupled flow and diffusion were all included.The influence of the temperature on the solute transport process was simulated by software COMSOL.The numerical results show that the temperature has an important effect on the concentration distribution of solute with time and soil depth,the thermal diffusion accelerates the solute transport and the process of thermos-osmosis,and heat consolidation retards the solute transport.When the transport time reaches 50 years,the transport depth of the solute under the temperature difference 70 K between upper and lower boundaries of clay liner slows down by 87.6%compared with that without the temperature difference.The fully coupled model can provide a theoretical support for the barrier design of the landfill and the evaluation of service life.