CHARACTERIZATION OF GEOTECHNICAL PROPERTIES OF LATERITIC SOIL – BENTONITE MIXTURES RELEVANT TO THEIR USE AS BARRIER IN ENGINEERED WASTE LANDFILLS

Abstract

The purpose of this study was to characterize lateritic soil – bentonite mixtures intended for use as low-permeability barrier in municipal waste disposal landfill. Characterization of the soil mixtures included measurement of Atterberg limits, compaction properties, hydraulic conductivity, shear strength, and desiccation shrinkage potential. Accordingly, laboratory tests involving soil mixtures with 0, 2.5, 5, 7.5 and 10% bentonite contents, prepared at varying compaction states (2% dry of optimum, optimum and 2% wet of optimum) and compacted using West African standard (WAS) compactive effort were carried out. Results show that mixtures with bentonite are adjudged to be suitable materials for liners because they met the statutory hydraulic conductivity requirement (i.e., k ? 1.0 x 10^-9 m/s). Acceptable volumetric shrinkage strain of £ 4% (a maximum allowable volumetric shrinkage found in literature and adopted by most regulatory agencies for barrier material) was maintained by most soil mixtures. Although, slight reduction in shear strength was established, unconfined compressive strength (UCS) values for all soil mixtures met or exceeded the general specification i.e., UCS ³ 200 kN/m² required for performance in waste repositories.