Engineering characteristics of compacted laterite soil as hydraulic barrier in waste containment application

Abstract

The primary objective of hydraulic barriers in containment facilities is to prevent migration of leachate directly into the underlying subsurface during both the active disposal period and the post-closure period. Liner system is, therefore, one of the most important elements of a modern sanitary landfill. In order to achieve an effective soil lining system, a minimum criterion of 30% fines content is required to fulfil the hydraulic conductivity requirement of ≤ 1 × 10-9 m/s as specified by most regulatory agencies and researchers. Studies reveal that at this percentage, laterite soils are vulnerable to leachate permeation, which will contaminate the groundwater. Therefore, this research aims to determine the effects of gradation on engineering properties of laterite soil with respect to hydraulic conductivity, volumetric shrinkage strain, and unconfined compressive strength. In order to satisfy the regulatory requirements of soil liner, tests were carried out on natural soil (30% fines) and two reconstituted soil samples (40% fines and 50% fines). The effects of fines content that is required to provide the recommended criteria of ≤ 1 × 10-9 m/s hydraulic conductivity, ≤ 4% volumetric shrinkage and ≥ 200 kN/m2 unconfined compressive strength at their permissible limits were plotted. The overall acceptable zone was obtained at moulding water contents ranged between 24-28% for 50% fines content. Based on the laboratory experimental results, a minimum fines content of 50% must be achieved to fulfil the engineering characteristics requirements to prevent groundwater contamination in tropical laterite soil.