黏土垫层水力–力学–化学耦合模型研究

在城市固废堆场建造运维、污染场地土壤、地下水围封阻隔等环境岩土、污染防治领域中,均会涉及到土体力学行为、孔隙水流动以及污染物运移之间的耦合作用问题。将土体的固结变形分为由力学荷载引起的力学固结变形及由化学荷载引起的化学–渗透固结变形,引入广义达西定律,并考虑土体物理特性和输运性质的动态变化,通过理论推导建立了适用于堆场黏土防渗垫层的水力–力学–化学耦合模型,模型最大的特点是实现了土体固结变形、孔隙流体流动与污染物运移过程之间的全耦合,各模型参数均能够体现耦合效应的影响。采用多场耦合有限元分析软件COMSOL Multiphysics对所建模型进行数值验证和求解,模拟结果表明:所建模型可从机理上描述水力–力学–化学全耦合过程,模拟结果与Peters和Smith模拟结果吻合较好,能够正确揭示超孔隙水压力、污染物浓度时空分布及土体固结变形的演化规律。

Coupled hydro-mechanical-chemical model for clay liner

The interconnection among mechanical behaviors of soil, pore water flow and contaminant transport is always involved in the fields of environmental geotechnical engineering and controlling of pollution. The related problems include the construction and maintenance of urban solid waste yards, and the protection of soil and groundwater from pollution. The consolidation deformation of soil is divided into two parts: mechanical consolidation deformation caused by mechanical loading and chemo-osmotic consolidation deformation caused by chemical loading. Then, based on the generalized Darcy’s law and considering dynamic variation of soil physical and transport properties, the coupled hydro-mechanical-chemical model for clay liner is established through theoretical deduction. The remarkable characteristic of the model is that it achieves a full coupling of the consolidation deformation of soil, pore fluid flow and contaminant transport processes. Furthermore, the parameters of the coupled model can also reflect the impacts of coupling effects. The finite element software COMSOL Mutiphysics is adopted to work out the solution of the proposed coupled model and verify its correctness. The numerical results illustrate that the established model can describe the coupled hydro-mechanical-chemical process through inquiring into mechanism., Moreover, the results agree well with those of Peters and Smith. The proposed model can accurately reveal the spatial and temporal distribution of the excess pore water pressure, contaminant concentrations and evolution consolidation deformation of soil.