Engineering geological evaluation of Mfensi and Afari clay deposits for liner application in municipal solid waste landfills

Abstract

Mfensi and Afari clay deposits in the Ashanti Region of Ghana were evaluated for their suitability as liner materials to curtail leachate migration in municipal solid waste landfills. Chemical, mineralogical, physicochemical, geotechnical, and thermal analyses were conducted to characterize the clays as well as to evaluate their potential as suitable barrier materials. The test results were compared with standard requirements for clay liner applications. The findings revealed that the chemical compositions of both clays were analogous with dominant oxides being silica, aluminum, and iron. Quartz, kaolinite, and magnetite were the minerals identified in both clays. The effective cation exchange capacity of the Mfensi and Afari clays was 5.45 meq/100 g and 28.99 meq/100 g, respectively. The clays were fine-grained (< 0.06 mm), with fines contents of approximately 80% and 56% for Mfensi and Afari clays, respectively. The Atterberg limits consisting of the liquid limits and plasticity indices of the Mfensi and Afari clays were 42.85%, 22.43%, and 64.78%, 40.52%, respectively. The unconfined compressive strengths were 331.73 kPa and 242.92 kPa for Mfensi and Afari clays, respectively. The hydraulic conductivities of the clays were of the order × 10−7 cm/s. The average thermal conductivities of the clays were found to be $$0.025\,{\text{Wm/K}}$$ for Afari clay and $$0.215\,{\text{Wm/K}}$$ for Mfensi clay. The results demonstrate that both clays generally passed the requirements for clay liner application and hence could be used as liner materials in municipal solid waste landfills to minimize leachate migration.