Pore-Scale Modeling of Polymer Clogging in Bentonite-Polymer Composite Geosynthetic Clay Liners: Fid-Bau Portal

Pore-Scale Modeling of Polymer Clogging in Bentonite-Polymer Composite Geosynthetic Clay Liners

Hou, Juan / Li, Hao / Gustitus, Sarah / Benson, Craig H.

Bentonite-polymer composite geosynthetic clay liners (BPC-GCLs) are used to line containment systems with leachates that are too aggressive for conventional sodium bentonite (NaB) GCLs to maintain low-hydraulic conductivity. Experimental observations indicate that the hydraulic conductivity of BPC-GCLs is affected by the properties of the polymer, the polymer loading and distribution, and the potential for the polymer to migrate and elute under a hydraulic gradient. In this study, pore-scale computational hydraulic models were developed and employed to simulate the movement of polymer in the intergranular spaces of BPC-GCLs. The model domain consisted of a collection of NaB granules and one or several globules of polymer gel. A pressure gradient was applied from the inlet to the outlet. Polymer viscosity, polymer loading, and the number and location of globules of polymer gel were varied between models. When polymer gel clogs open pores, lower hydraulic conductivity is achieved because flow is directed through fewer channels and more tortuous pathways. Lower viscosity polymer gels are eluted more readily than higher viscosity polymer gels, leading to higher hydraulic conductivity. Polymer loading, location, and distribution also affect hydraulic conductivity. BPC-GCLs with identical polymer loading and different distributions of polymer had hydraulic conductivity differing orders of magnitude. The findings suggest that BPC-GCLs can be engineered to achieve different outcomes by varying the hydrodynamic properties of the polymer, the polymer loading, and the distribution of the polymer in the pore space.