Numerical investigation on hydraulic and gas flow response of MSW landfill cover system comprising a geosynthetic clay liner under arid climatic conditions. Issue 6 (December 2022)

• Record Type: Journal Article
• Authors: Khan, Vishwajeet; Roy, Suman; Rajesh, Sathiyamoorthy
• Is Part Of: Geotextiles and geomembranes. Volume 50:Issue 6(2022)
• Page Start: 1159
• Page End: 1171
• Publication Date: 2022-12
• Subjects: Cover system -- Geosynthetic clay liner -- Hydraulic behavior -- Gas flow behavior -- Climatic conditions -- Numerical coupled model; Membranes (Technology) -- Periodicals; Membranes (Technology); Periodicals; Electronic journals; 624.189
• DOI: 10.1016/j.geotexmem.2022.08.001
• Languages: English
• ISSNs: 0266-1144

Abstract

Abstract: Municipal solid waste (MSW) landfill cover systems are designed to minimize the infiltration of rainwater into waste and to mitigate the biogas emissions to the atmosphere. In the present study, the efficacy of such a landfill cover system consisting of a Geosynthetic clay liner (GCL)in mitigating the hydraulic flow and gas emissions under arid climatic conditions was investigated critically. For this purpose, the water retention curve (WRC), hydraulic conductivity function, and gas flow characteristics of the chosen GCL were studied through experimental methods in the laboratory. The unsaturated transient state seepage analysis utilizing coupled hydraulic and gas flow mechanisms was performed in the study to assess the performance of the cover system. The results obtained from the experiments were used as input parameters. The effect of drying/desiccation and the self-healing nature of GCL due to climatic changes were also analyzed by exposing the GCL directly to the climatic boundary for one year. It was observed that the GCL present in the chosen cover system effectively functions as a hydraulic barrier in arid climatic conditions. However, during the summer and winter seasons, an increase in gas flow from 0.02 g/h/m 2 to 24.7 g/h/m 2 was observed, probably due to the drying anddesiccation of GCL. Interestingly, due to the self-healing nature of the GCL, gas flow through the cover system was substantially reduced to 0.02 g/h/m 2 during the rainy season. The effect of drying was more pronounced when the GCL was exposed to the climatic condition, leading to an early gas breakthrough and an increase in gas flow from 0.02 g/h/m 2 to 957 g/h/m 2 . The percolation through the cover system remains considerably low throughout the year, mostly due to the unsaturation and low hydraulic conductivity in GCL. A cumulative percolation close to 0.1 m 3 was observed at the end of one year in arid climatic conditions. Highlights: Numerical investigation of landfill cover system with GCL in mitigating hydraulic flow and gas emissions. Water retention curve, hydraulic conductivity function, and gas flow characteristics of GCL were established. Assessment of desiccation and self-healing nature of GCL due to climatic boundary conditions. Temporal variation of suction, volumetric water content, gas mass flux, and net percolation of the cover system was monitored. Effect of desiccation is pronounced when GCL was exposed to climatic conditions, leading to an early gas breakthrough.