CONTROL OF SHRINKAGE IN COMPACTED LATERITIC SOIL TREATED WITH BENTONITE

Abstract

Although the potential for desiccation induced shrinkage exists when fine grained lateritic soil bentonite mixture is used as liner and cover material in waste landfills, appropriate design measures and construction techniques can control this phenomenon and thus minimize the problems associated with it. This paper presents a method of controlling shrinkage that delineates compaction conditions within which the compacted soil will exhibit volumetric shrinkage allowed for such projects. In the study, volumetric shrinkage strain measurements were made desiccating soil samples containing 0-10% bentonite by dry weight prepared at moisture contents ranging from 10-20% and compacted with four energy levels namely Reduced British Standard Light (RBSL), British Standard Light (BSL), West African Standard (WAS) and British on Standard Heavy (BSH). Results of the study indicate that all samples exhibited volumetric shrinkage with the amount of shrinkage increasing with higher bentonite content and increasing moisture content. The measured shrinkage strains were related to water content and dry unit weight in an acceptable zone on the water content dry unit weight curve. Data points within the acceptable zone represent test results with shrinkage strain of ≤4%. This approach will ensure good control over the quality of compacted soils as well as compliance with requirement of ≤ 4% normally specified by most regulatory agencies for shrinkage strain.