Mineralogy and Geotechnical Properties of Fine-Grained Sediments from Swali Community

The mineralogical and geotechnical properties of fine grained deposits from Swali community, in Yenagoa local government area of Bayelsa State, Nigeria were analyzed using X-ray diffraction (XRD) for the qualitative analysis of the mineral composition and the Atterberg limit using ASTM D 4318 standard for the geotechnical properties. Four representative samples that were analyzed using XRD show the deposit is composed of quartz, albite, orthoclase and muscovite with average values of 59.25%, 16.45%, 13.25% and 11% respectively. No typical clay mineral was observed in the analysis. The mineral suite indicates an acid igneous rock source and long distance and time of travel. Ten samples were analyzed for the geotechnical properties, and the Atterberg limits derived are: Liquid limit ranging from 29.7% – 50.4%, Plastic limit ranging from 22.9% – 36.1% and the Plastic Index ranging from 11.4 – 26.1. Four of the samples were non plastic and only six show a measure of plasticity. The deposits are classified as inorganic lean clay in locations SW6 and SW10 designated as CL as they fall above the A – Line and have Plasticity Index > 7, and those from SW2, SW3, SW4 and SW8 are classified as silty clay with designation ML because they fall below the A – Line on the plot of Liquid limit versus Plastic Index but have Plasticity Index > 4. All the deposits have low plasticity because they fall below the Liquid limit separator line of 50% with only one on the borderline. Therefore, the deposit range from inorganic lean clay to silty clay with low plasticity derived from an acid igneous rock with long distance and time of travel.