Effect of compaction water on strength and hydraulic properties of bentonite based liner

Abstract

Abundance of pond ash and its resemblance with natural sand encourages its use as a substitute to sand in sand-bentonite (SB) liner material. Compaction water content influences the geoengineering properties of cohesive soil to a great extent. Accordingly, compaction, strength, permeability and shrinkage characteristics of both pond ash-bentonite (PAB) and SB mixes are investigated at standard and modified Proctor compaction energies at various water contents to support the recommendation of PAB mixture as an alternative landfill liner. At similar compaction conditions, PAB mix exhibits higher unconfined compressive strength (UCS) and hydraulic conductivity than that of SB mix. The UCS values of the dry-side compacted mixes are higher than those of the wet-side of compacted mixes. Dry-side compacted mixes shows a reduction in hydraulic conductivity with permeation time whereas; no substantial reduction in hydraulic conductivity is noticed for wet-side compacted mixes. Furthermore, the volumetric shrinkage of both PAB and SB mixes are within the permissible value of 4%, for a wide range of water variation from dry to wet-side of optimum. The observed mechanical properties are correlated to the shape of coarse fraction particle and the corresponding microstructural arrangements of the compacted specimens.