Probabilistic soil-rock degradation due to heavy metal existence in Tashan-Kaji, Toro LGA (Nigeria)

Purpose. To evaluate the impact of heavy metal contamination, specifically lanthanum (La) and iron (Fe), on the geotechnical characteristics of soil in Tashan Kaji Village, Toro LGA, Nigeria. The area has been experiencing recurrent infrastructure failures, particularly roads and buildings, which may be linked to soil degradation caused by heavy metal presence. Methodology. Ten soil samples were collected from various locations using the auger boring technique. The samples underwent physical and mechanical testing (Atterberg limits and standard Proctor compaction tests) and geochemical analysis using X-ray fluorescence (XRF). The results were statistically analyzed to explore the relationship between heavy metal content and soil behavior. Findings. The soils showed moderate to high plasticity and contained significant concentrations of La and Fe. High La content (95–96 %) and low Fe content (0–3 %) adversely influenced key geotechnical parameters. Increased La levels correlated with higher plasticity, while reductions in Fe content were associated with diminished MDD (maximum dry density) and OMC (optimum moisture content). A coherent statistical relationship was established between heavy metal concentration and changes in soil properties. Originality. This study offers a novel investigation into the specific influence of La and Fe on soil plasticity and compaction characteristics in a localized Nigerian context, contributing to the limited body of literature on heavy metal-induced geotechnical degradation. Practical value. The findings provide critical insights for civil and environmental engineers, aiding in assessing and mitigating infrastructure risks in regions affected by soil contamination. Understanding the influence of La and Fe can guide material selection, foundation design, and soil treatment in similar geotechnical settings.