Geotechn ical Assessment of Clay Deposits in Minna, North - Central Nigeria for Use as liners in Sanitary Landfill Design and Construction

Abstract

Sanitary landfills are waste disposal method that functions without creating nuisance to the environment. It confines waste to the available area, reduce waste to the minimum practical volume. The waste in a landfill reacts to release a cocktail of contaminantscalled leachate, which posses treat to the surrounding environment (soil and groundwater).Therefore, barrier soils are required for the lining of a landfill to prevent seepage of leachate into the surrounding groundwater and subsequent contamination of the groundwater system. Some clay in Minna was assessed using geotechnical techniques to determine its suitability as barrier soils. Five samples of clay were subjectedto grain size analysis, atterberg limits, compaction tests and mineralogy test. From the grain size analysis and the atterberg limit, the soil is classified as a clayey material. The liquid limit ranged from 45.5%-61% with a mean value of 51.8% which is an indication of high plasticity and low hydraulic conductivity, the plastic limit ranged from 29.2%-35.8% with a mean value of 32.44% and its plasticity index ranged from 13.7%-25.2% with a mean value of 19.37% which implies that the clay can withstand volumetric shrinkage on drying and exhibit a low to medium swelling potential when wet. The compaction test reveal an optimum moisture content(OMC) ranging from 17.7% to 24% with a mean value of 19.94% and a maximum dry density (MDD) that varied from 1.59g/cm3 to 1.76g/cm3with a mean value of 1.7g/cm3. This results of these geotechnical analysis suggests that the clay in the area meets the requirement for a barrier soil. The X-ray diffraction analysis reveals the presence of kaolinite dominated clay and mixedclay (kaolinite-illite). These minerals have the capability to attenuate and contain leachates from wastes. Hence, the studied clays are good barrier soils.