化-渗耦合作用下黏土类工程屏障重金属污染物阻滞性能演变机理

针对重金属污染场地黏土类工程屏障长期阻滞性能评价问题，以红黏土-膨润土混合土材料为研究对象，开展元素与模型试验、理论研究和数值模拟分析，阐明化-渗耦合作用下红黏土-膨润土工程屏障重金属污染物阻滞机理。研制“土体等压变形-化学渗透-溶质迁移联合测定仪”，据以开展化学渗透、变形及污染物协同迁移等试验，揭示土体中渗透吸力梯度诱发渗流、变形与污染物迁移机理；在此基础上，开展模型试验，考察渗透吸力梯度作用下、重金属污染物在黏土类工程屏障中迁移规律及阻滞过程；借助压汞等微观测试手段，分析工程屏障阻滞性能发挥过程中孔隙结构演化规律；结合理论分析，建立化-渗耦合作用下基于黏土材料孔隙结构演化的溶质迁移耦合模型；借助数值分析方法，确定工程屏障设计厚度及运营寿命等参数，实现考虑化-渗耦合作用的黏土类工程屏障性能评估。预期成果可为我国重金属污染场地的工程屏障系统设计、施工和安全性评估提供可靠的理论依据。

In order to study the long-term retention performance of the clayey engineered barrier in heavy metal contaminated sites, element and model tests, theoretical and numerical analysis will be performed on the laterite-bentonite mixture to clarify its retention mechanism to heavy metal contaminants under chemo-osmosis coupling conditions. Firstly, the "soil isobaric deformation - chemo osmosis - solute migration joint measurement instrument" will be developed to conduct the experiments of chemo-osmosis, deformation and contaminant coordinated migration, aiming to reveal the coupling mechanism of seepage, deformation and contaminant migration induced by osmotic suction gradient in soil. Secondly, model tests will be carried out to investigate the migration law and retention mechanism of heavy metal contaminants in the clayey engineered barrier under osmotic suction gradient. Subsequently, the pore structure evolution of engineered barrier during the retention process will be investigated by microstructural tests such as mercury intrusion porosimetry (MIP). Finally, based on the experimental results and theoretical analysis, a solute migration coupling model in consideration of the pore structure evolution of the clayey materials under chemo-osmosis coupling conditions will be established. To further evaluate the retention performance of clayey engineered barrier considering chemo-osmosis coupling effects, numerical methods will be used to estimate the reasonable construction thickness and lifespan of the engineered barrier. The achievements of this project are expected to provide a reliable theoretical basis for the design, construction and safety assessment of engineered barrier system in heavy metal contaminated sites in China.