Soil Erodibility Characterization of the Southwestern Nigerian Basement and Sedimentary Terrains Using Geochemical and Geotechnical Techniques

Our lack of full understanding of the factors affecting erodibility in all geological terrains, especially the combined geochemical and geotechnical effects, remains a challenge in geotechnical engineering.

In this research, the erodibility of soils from basement and sedimentary terrains, Southwest Nigeria, was investigated through a combined geotechnical-geochemical approach.

The soil samples from Akure (Basement Complex of Nigeria) and Ode-Irele (sedimentary basin) were tested for classification, consistency limits, compaction, California Bearing Ratio (CBR) and X-ray fluorescence (XRF).

The findings reveal that basement soils have higher sesquioxides (Al O + Fe2O ) content, laterization, bonding, cohesion (as high as 120.2 kPa), internal friction angle (as high as 32.9°) and CBR values (as high as 70 %), well-graded, coarse grained clayey soil and classified as CI - CH soils.

By contrast, sedimentary soils contain higher SiO , lower cohesion (2.0 kPa), well-graded, coarse grained silty sand soil and classified as CL - ML soil type.

Soils found on basement terrain have better bonding, are less erodible and are more amenable to stabilization than sedimentary terrain soils (STS).

In comparison, STS have lower cohesion-frictional characteristics, higher erosion, soil loss, and soil degradation potential.

The greater soil loss ratio and erodibility factors for STS reflect their susceptibility to environmental degradation and landslides.

These variations in soil properties reflect different geological formation histories, which result in different degrees of weathering, soil structure and permeability.

This study underscores the need to consider terrain-specific soil characteristics for erosion risk analysis and infrastructure development.