Breakthrough time-based design of landfill composite liners

Breakthrough time based design methods for determining the design thickness of landfill composite liners are proposed. The composite liners consist of either 1) a geomembrane (GMB) and a compacted clay liner (CCL), 2) a geomembrane (GMB), a geosynthetic clay liner (GCL) and a soil liner (SL), or 3) a GCL and a SL. The design methods are based on analytical solutions developed for solute advection and dispersion of leachate contaminants in composite liners. Both solute concentration and solute flux are considered in the analyses. Two dimensionless parameters involving contaminant concentration and contaminant flux are introduced and the design curves are proposed for breakthrough time based design of composite liners. The results obtained by the proposed analytical solutions are in good agreement with the experimental data published in the literature. Illustrative examples are presented to demonstrate the application of the design methods for composite liners consisting of a GMB and a compacted soil liner and those consisting of a GMB, a GCL, and a SL. The effect of leachate head on the design thickness of composite liners was investigated. It is shown that the design methods presented in this paper is easy to be used to design the landfill composite liners in different leachate head cases.