Pore scale polymer migration in BPC-GCLs influenced by PSD, bentonite swelling, and polymer location

Abstract

The study investigates the hydraulic behavior of bentonite-polymer composite geosynthetic clay liners (BPC-GCLs), focusing on the effects of particle size distribution (PSD), polymer location near the inlet and outlet, swelling-induced pore structure evolution, mobile porosity, and polymer migration using COMSOL Multiphysics. The results indicate that the spatial distribution and migration behavior of the polymer have a significant influence on fluid transition patterns. When located near the inlet, the polymer undergoes a three-stage migration process involving progressive deformation, entrapment, and eventual immobilization in narrow pores, resulting in a significant and irreversible reduction in porosity from 0.099 to 0.007 and a decrease by four orders of magnitude in hydraulic conductivity. In contrast, polymers near the outlet initially undergo clogging, followed by hydraulically driven elution, resulting in a more gradual and more minor reduction in porosity, from 0.101 to 0.071, and a one-order-of-magnitude decrease in hydraulic conductivity. The pressure distribution within the domain reflects the evolving hydraulic response to polymer migration, where localized pressure buildup corresponds to pore clogging. In contrast, subsequent pressure equalization signifies the progressive elution of polymer and the restoration of flow paths. These findings demonstrate the critical role of pore-scale heterogeneity and spatial polymer location in dictating the sealing performance of BPC-GCLs. This multiphysics framework provides a robust foundation for designing and optimizing polymer-enhanced barrier systems in environmental and geotechnical engineering.