Effect of minerals on the threshold of compacted clay material liners and service life of barriers in municipal solid waste landfills.

Clay is widely applied in landfill projects because of its low permeability. However, it is often ignored that clay exhibits the characteristic of threshold gradient i₀, and i₀ can exert a certain impact on the service life of landfill barriers. To this end, this paper first conducted permeability tests on seven clays to study the permeation law of these clays and found that the higher the montmorillonite and illite content in compacted clay, the higher i₀ was, and the higher the kaolinite and sand content, the lower i₀ was. By summarizing previous studies and this paper, a suitable power function relationship between i₀ and the intrinsic permeability not only applies to the clays but also to the mixed soils (Kao-H and Clay-J, Kao-H and Bent-H, and Clay-J and Sand-F). Furthermore, based on the experimental conditions, considering that compacted clay is subject to i₀, numerical analysis of the liner service life was conducted for single-layer and composite liners using three types of pollutants (Cd, COD and DDT) under leachate heads of 0.3 and 20 m. Under a leachate head of 0.3 m, the single-layer compacted clay barrier was only penetrated by COD at i₀ = 0. In the other cases, both the single-layer compacted clay liner and composite liner could satisfy a service life of 100 years. Under a leachate head of 20 m, the service life of the barrier gradually increased with increasing i₀. For both forms, i.e., single-layer and composite liners, the barrier breakdown indicator pollutant was COD when considering the non-Darcy seepage effect. [ABSTRACT FROM AUTHOR]