A one-dimensional analytical model is proposed to analyze contaminant diffusion through a composite geomembrane cut-off wall (CGCW) composed of a geomembrane (GMB) and a bentonite cut-off wall (BCW). The model considers degradation process of contaminant and time-dependent inlet boundary condition which are common in engineering practices. Moreover, two limiting scenarios of the exit boundary condition (EBC) of CGCW for field conditions are taken into account, including the flushing and non-advective semi-infinite aquifer EBCs. The influence of boundary conditions and performance of CGCW are comprehensively investigated. The results show that the upper and lower limits of the mass flux of the exit face of CGCW can be obtained by the models with flushing EBC and the model with non-advective semi-infinite aquifer EBC, respectively. In addition, degradation has substantial influence on the contaminant migration, and smaller half-life in BCW results in smaller contaminant leakage. The performance of CGCW can be improved by embedding GMB at a proper location which is related to the type of contaminant and EBC. Furthermore, thickening HDPE GMB or adopting a coextruded EVOH GMB is efficient to improve the performance of CGCW. The present model can be used as an applicable tool for rational design of CGCW.

提出了一种一维分析模型来分析污染物通过由土工膜 (GMB) 和膨润土防渗墙 (BCW)组成的复合土工膜防渗墙 (CGCW) 的扩散。该模型考虑了工程实践中常见的污染物降解过程和瞬态入口边界条件。此外，考虑了现场条件下 CGCW 出口边界条件 (EBC) 的两个限制场景，包括冲刷和非对流半无限含水层EBC。全面研究了边界条件和 CGCW 性能的影响。结果表明，CGCW 出口面质量通量的上限和下限分别可由具有冲洗 EBC 的模型和具有非对流半无限含水层 EBC 的模型获得。此外，降解对污染物迁移有重大影响，BCW 中较小的半衰期导致较小的污染物泄漏。CGCW 的性能可以通过在与污染物类型和 EBC 相关的适当位置嵌入 GMB 来提高。此外，增稠 HDPE GMB 或采用共挤 EVOH GMB 可有效提高 CGCW 的性能。该模型可作为CGCW合理设计的适用工具。