Geoenvironmental behaviour of lead-contaminated clay with sawdust

Abstract

Clayey composite liners are appointed in modern landfills to isolate wastes from the environment and minimise the escape of contaminants that are affecting the groundwater and the subsoil. Enhanced compressibility and reduced permeability are considered favourable; however, the ameliorating liners are at risk of losing these properties and thus the ability to contain the contaminant due to changing pH and contaminant contents during the long course of service. This research investigated the change in the mechanical properties, namely, the compression index c c, permeability coefficient K and void ratio–effective stress curve e against log σ′ of bentonite clay treated with chemically modified sawdust contents and laced with various lead nitrate (Pb(NO3)2) concentrations. The optimum values were simultaneously achieved for c c and K, in the 10% sawdust of pH 10 design, with lead (Pb) concentration <150 cmol/kg soil, and in the 30% sawdust of pH 10 design, with lead concentration between 150 and 250 cmol/kg soil; therefore, these were the optimum designs with best returns in terms of the given geotechnical properties, for the given lead concentrations. In both acidic and alkaline states, K decreased in different lead concentrations, with the introduction of the 10–30% sawdust, which is the range of amount proposed in field applications.