Journal of Earth Sciences and Geotechnical Engineering

Effect of Disturbed Soil Properties on Gully Growth/SoilLoss at Underground Drainage Construction Site, UYO

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• Abstract

  Physico-chemical and erodibility characteristics of soil under anthropogenic disturbance by mechanically land-grading along the underground (tunnel) drainage construction sites in Uyo, Nigeria were investigated using standard methods and correlated with gully growth and soil loss. Statistical and parameter analyses evaluated spatial variability, correlations and significant differences. The disturbed soil had predominantly coarse grain sands(86%), low fines (<10%), high bulk density, low total porosity and very low permeability, indicating compacted, homogenous texture from the crest to the tunnel bottom, but permeability showed significant variability ( CV> 40%). Soil chemical properties had low correlations with gully morphometric degradation and soil loss; however, physical properties, particularly low clay and silt content, total sand, and bulk density highly reduced gully geometric degradation and volume of soil loss. Large proportions of bases (Ca⁺⁺ and Mg⁺⁺) sufficiently reduced SAR, hence reduced soil erodibility at base sites. Silt and clay correlated highly with width and depth increments, and volume loss (r = 0.70–0.78) down the slope but longitudinal degradation was the resultant effect of runoff on the steep side-slope. Clay, silt, total sand and bulk density moderately reduced width and depth erodibility, correlating with 60% of volume loss.