Influence of polymer enhancement on water uptake, retention and barrier performance of geosynthetic clay liners

• Published in: Geotextiles and geomembranes 2022-08, Vol.50 (4), p.590-606
• Main Authors: Lau, Zhi Chong, Bouazza, Abdelmalek, Gates, Will P.
• Format: Article
• Language: English
• Subjects: Adsorbed water; Bentonite; Clay; Clay liners; Curve fitting; Expulsion; Extrusion; GCLs; Geochemistry; Geosynthetics; Geotechnical fabrics; Hydration; Interlayers; Measurement methods; Polymers; Suction; Swelling; Unsaturated; Water; Water retention curves
• ISSN: 0266-1144; 1879-3584
• DOI: 10.1016/j.geotexmem.2022.02.006

This paper explores the influence of polymer enhancement on water uptake and retention by geosynthetic clay liners (GCLs) across a wide suction range (up to 106 kPa), including the low suction regime (0.1–10 kPa) typically omitted in past studies. The suction measurement methods used enabled elucidation of water uptake and retention behaviour through the framework of GCL pore structures and their corresponding suction regimes. Polymer enhanced GCLs (PE-GCLs) have high maximum water uptake, and both the water entry and air expulsion values tend to be high. Due to high swelling, the onset of geotextile confinement for PE-GCLs was observed at high suctions. The impact of polymer becomes more apparent when the bentonite achieves a pseudo-two-layer interlayer hydration state at a suction of about 40 MPa (RH = 75%). The hydration mechanism for the polymer fraction in bentonite is unique to the specific polymer type, polymer dosage, and manufacturing process. The water retention behaviour at the low suction range is caused by the in-filling of geotextile pores, bentonite swelling and extrusion, and polymer water adsorption. Insights from this study can form the basis for developing a more suitable bimodal generalised model for fitting the water retention curves of GCLs. •Polymer enhanced GCLs (PE-GCLs) have high maximum water uptake.•The impact of polymer is apparent when bentonite achieves a pseudo-two-layer interlayer hydration state.•The hydration mechanism for the polymer fraction in bentonite is unique to the specific polymer type, dosage and manufacturing process.•The water retention behaviour at low suction is caused by geotextile pores filling.•And also by bentonite swelling and extrusion and polymer water adsorption.