Geological and geotechnical assessment of gully erosion sites in parts of Uturu, Southeastern Nigeria

Nwankwoala, H. O., Ahiakwo, E., Akudo, E. O., Okeke, C. and Abija, F. A.

African Journal of Engineering Research
Published: September 7 2022
Volume 10, Issue 2
Pages 17-23

Abstract

This study aims to assess the hydrogeological and geotechnical characteristics of gully erosion sites in Uturu and its environs. Standard hydrogeological and geotechnical investigation methods were adopted in this study. A field geological study of the area revealed that it is covered by sedimentary rocks. The soils are lateritic and are the product of intensive weathering that occurs under tropical and subtropical climatic conditions resulting in the accumulation of hydrated iron and aluminum oxides. Results of sieve analyses show that the soils at the gully sites have sorting values ranging between 0.42 and 2.3 coefficient of uniformity values ranging between 3.0 and 10, and coefficient of curvature values ranging between 0.2 and 1.3. These indicate that the soils are fair to well-sorted in those places. The plasticity index values ranging between 11.0 and 29 with a mean value of about 20 indicate soils of moderate to high plasticity, slight dry strength and easily friable. Values of maximum dry density range between 1.83 and 2.12 g/cm³ at optimum moisture contents of between 7.4 and 11.3% revealing that the soils were generally loose. The hydraulic conductivity and transmissivity values as determined from the statistical grain size method range between 3.8 × 10^-4 to 6.4 × 10² cm/s and 3.8 × 10^–2 to 9.6 × 10⁴ cm² respectively. These indicate moderate seepage fluxes and adverse pore pressures and are thus easily erodible. From the geotechnical analysis results, recommendations for erosion control such as aforestation and construction of drainages were suggested.

Keywords: Hydraulic conductivity, geotechnical, erosion, gullies, plasticity, Uturu.

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