Geotechnical Properties Improvement of Erosion Susceptible Soil with Caustic Soda (A Case Study of Ekosodin, Benin City)

Abstract

The presence of the University of Benin (UNIBEN) makes the Ekosodin community economically vital, with local businesses benefiting from the spending of students and staff. Consequently, it is essential to address the problem of soil erosion in the area to facilitate ongoing development and growth. The aim of this study was achieved by collecting four soil samples and analysing various properties such as specific gravity, particle size distribution, Atterberg limits, optimum moisture content, maximum dry density, cohesion, angle of internal friction, and California bearing ratio. The study also examined the impact of adding caustic soda at different concentrations. The resulting unstabilized soil exhibited AASHTO class A-6 and A-7-6 characteristics, featuring a significant proportion of clayey soil with more than 35% passing through sieve No 200, resulting in a fair to poor subgrade rating in pavement design and significant compressibility. Nevertheless, as the percentage of caustic soda increased, there was a reduction in the liquid limit, plastic limit, plasticity index, optimum moisture content, and angle of internal friction. Additionally, higher maximum dry density, cohesion, unsoaked and soaked California Bearing Ratio (CBR) values were recorded with increased caustic soda content. The highest soaked soil CBR value of 26.0% was achieved with a 10% caustic soda stabilization. Therefore, chemical stabilization using caustic soda is recommended for erosion-prone soil in Ekosodin, as it transforms the area's soil from a poor subgrade or foundation to a robust load-bearing material suitable for building and road construction.