GCL复合垂直防渗墙是由水泥膨润土泥浆墙和膨润土防水毯(Geosynthetic clay liners，GCL)组成的一种新型竖向防渗阻污墙，其中双幅GCL搭接所产生的绕渗，对此类防渗墙防渗阻污性能的下降具有潜在的影响，目前研究中尚缺乏对该类影响的分析。本文通过建立含GCL搭接区的复合垂直防渗墙的二维污染物运移模型，并基于数值计算方法综合考虑了GCL搭接宽度B2、搭接区渗透系数kp、水泥膨润土墙厚度Lw和渗透系数kw对搭接区内污染物分布规律及临界搭接宽度的影响。计算结果表明:GCL搭接宽度影响复合垂直防渗墙内污染物浓度的分布规律，增加B2且未达到临界宽度(污染物同时击穿搭接区和无搭接区GCL层)，导致GCL复合垂直防渗墙击穿时间延长；GCL搭接区入口边界污染物浓度总体高于出口边界处，且kp和Lw越小，或kw越大，搭接区横向入口和出口边界处浓度差别越明显；减小kp或kw，导致GCL临界搭接宽度明显减小，但复合垂直防渗墙最终击穿时间趋于与无搭接单层GCL层击穿时间相同；水泥膨润土墙厚度Lw越大，临界搭接宽度则越小，且Lw由0.4 m增加1倍至0.8 m时，防渗墙被击穿时间延长约2.5倍。

GCL composite vertical anti-seepage wall is a new type of vertical anti-seepage and the wall composed of cement bentonite slurry wall and geosynthetic clay liners (GCL). The overlap of the two GCLs has a potential impact on the decline of anti-seepage and pollution control performance of such anti-seepage walls, and there is currently a lack of analysis of such effects in research. A two-dimensional pollutant migration model was presented in this study, and the comprehensive analysis of the effect of GCL overlap width, B2, permeability coefficient of GCL overlap area, kp, the thickness Lw and permeability coefficient kw of cement-bentonite wall on the transversal distribution of pollutant and critical GCL overlap width were carried out on the basis of numerical simulation method. The calculation results showed that the GCL overlap width affected the distribution mode in the GCL composite vertical barrier wall, and increasing the B2 but not reaching the critical GCL overlap width (corresponding to the moment of pollutant breaking through the GCL overlap width and non-GCL overlap range) caused to the increase of breakthrough time of GCL composite vertical barrier wall. Generally, pollutant concentration at the inlet of GCL overlap area is higher than that at the outlet of GCL overlap area, especially for the scenario of the smaller kp or Lw, or the greater kp. The decrease of kp or kw resulted in remarkable reduction of the critical GCL overlap width, whereas the breakthrough time tends to be the same as that in the GCL composite cut-off wall with non-GCL overlap width. In addition, to increase the thickness Lw of cement-bentonite wall caused the decrease of the required critical GCL overlap width. Moreover, a two-fold increase in Lw from 0.4 m to 0.8 m caused a 2.5 times increase of the breakthrough time of GCL composite vertical barrier wall.