Geotechnical Characterization and Stabilization of Gully Erosion Soils at Auchi, Anambra Basin Southeastern Nigeria

Abstract

Gully erosion is a severe ecological concern in Auchi and its environs, which has led to destruction of lives and properties. Termite reworked soils have been observed to possess improved engineering properties and have over the years been used to improve soil properties. This research therefore seeks to mitigate the effects of the erosion by stabilizing the gully soils using termite-reworked soils of different genetically diverse origins. Soils from gully walls and beds from two gully erosion sites in the Auchi area and termite-reworked soils from different geological terrains were sampled. All the soils were analyzed for the determination of natural moisture content, grain size analyses, and Atterberg limits. The gully soil samples were thereafter compacted with termite-reworked soils at optimum blending ratio ranging between 27 to 50% by weight gotten through an arithmetic method by adopting grading limits for soil-aggregate mixtures. Shear strength parameters were determined on the compacted soils at OMC. The results revealed that the gully soil is non-plastic unconsolidated poorly graded sand with uniformity coefficient between (1.70-2.50), coefficient of curvature (0.77-1.15), natural moisture content between (4.00-9.00), while the termite reworked soils of both terrains are fairly graded inorganic soil of low to medium plasticity composed of kaolinite as the dominant clay mineral, indicating non-swelling and shrinkage potentials. Both termite-reworked soils are classified as lean clay soils, indicative of their suitable binding properties. The gully soils possess low maximum dry density showing the soils are unconsolidated and friable while the effect of the stabilization increases the MDD and reduces the OMC. Pre-stabilized gully soils have an average cohesion value of 15.5 KN/m2 indicating a very loose soil while the SBT (Sedimentary base termitarium) stabilized gully soil and the BCT (Basement complex termitarium) stabilized gully soil have an average cohesion value of 51.3 KN/m2 and 57.3 KN/m2 indicating the presence of binding material. Conclusively, blending of gully soil with termite-reworked soils significantly enhanced the cohesion between the grain particles of the gully soils, improved its strength and can thus help prevent gully.