Geotechnical and Geochemical Assessments of Shales in Anambra Basin, Southeastern Nigeria, as Landfill Liners

Abstract

The use of landfills as containment for municipal solid waste management has received wide acceptance the world over. Its development in countries like Nigeria is constrained by high cost and scarcity of synthetic liners in the local markets. Exploration of the abundant locally available clay deposits in the country’s sedimentary Basins will prove economical, provided it satisfies the standard specifications for design and construction of landfill liners. This study thus evaluates the suitability of shales from three formations (Enugu, Ameki and Imo) within Anambra Basin of Southeastern Nigeria as liner materials. Geotechnical tests such as particle size distribution, Atterberg’s limits, compaction, coefficient of permeability and consolidation were performed on the shale samples. Geochemical analyses involving the inductively coupled plasma emission spectroscopy (ICPES) and cation exchange capacity (CEC) were also conducted; all employing standard methods. Based on the Unified Soil Classification System (USCS), Enugu and Imo shales contain high-plastic inorganic clay, while Ameki shales comprise low–medium-plastic inorganic clay. Coefficient of permeability result ranging from 9.12 × 10−6 to 2.14 × 10−6 cm/s indicates an increase above the standard specification. Expectedly, the cation exchange capacity (CEC), compressibility and plasticity index of the shales are positively related suggesting strong influence of the geotechnical properties on their sorption potentials. Overall assessment revealed that the high hydraulic conductivity and swelling potentials of the shales are not suitable for natural clay liners. Nevertheless, Enugu and Imo shales can further be stabilized chemically to the desired hydraulic conductivity of liners considering other suitable geotechnical properties and their CECs.