Unsaturated permeability of compacted clay liner under linear adsorption conditions

Abstract:

The compacted clay liner (CCL), the main anti-seepage facilities in landfill and generally made up of clayey soil, will adsorb the contaminants of the leachate when it prevent the leachate from polluting the groundwater and surrounding soils. The permeability of the CCL is affected by its microscopic pore structure changes due to the adsorption of clay. It is assumed that the adsorption of contaminants on the CCL is in accordance with the linear model, the pore distribution in the CCL is uniform and it is only affected by the adsorption. Based on the conservation of volume and mass, an empirical formula was presented for CCL to evaluate the changes of porosity induced by the adsorption. Meanwhile, a new unsaturated permeability model was also suggested considering the adsorption effects of contaminants on the CCL pore structure. Finally, the effects of adsorption of CCL on its unsaturated permeability were analyzed by numerical calculation. The results show that the adsorption of contaminants on CCL can reduce the porosity and improve the performance of seepage-prevention of CCL. Taking the adsorption effects into account, the unsaturated permeability of the CCL is significantly affected by the adsorption distribution coefficient, contaminant concentration, initial porosity and effective saturation. The studies may be helpful to the selection of materials of CCL, provide theoretical references for designing of CCL, and ensure the safe disposal of municipal solid waste.