Study for two-dimensional transport of organic pollutant in the composite cutoff wall-aquifer system with a defective geomembrane considering the consolidation behavior.

For composite cutoff walls (CCWs) containing geomembranes, the geomembrane is commonly found with defects, and the engineering properties of barrier materials (e.g., soil-bentonite) usually alter with depth due to the consolidation behavior. However, the impacts of these factors on the transport laws of pollutants remain unclear. In this study, aiming at the CCW-aquifer system containing a defective geomembrane, a novel theoretical model for two-dimensional transport of organic pollutant considering the effect of consolidation behavior is established. Then, this model is numerically solved and is fully validated through several comparisons, including the comparison with the experimental measurements. Following this, the investigation finds that, compared with ignoring the consolidation behavior, the upper concentration in the CCW increases but the bottom concentration declines when this behavior is considered. The concentration is higher when accounting for the presence of geomembrane defects as compared to the scenario where a geomembrane is thought to be intact, and their difference grows with an increasing hydraulic head difference. Furthermore, the influences of several factors on the CCW's barrier performance are quantitatively assessed. Eventually, a defective geomembrane's anti-seepage function is visually exhibited through the comparative study with the single-layered cutoff wall's barrier performance. Overall, this study helps to reasonably evaluate the CCW's barrier performance, and offers guidance for the application of geomembranes in pollution-control engineering.