Enhancing Subgrade Performance of Berea Red Soil: Biopolymer Stabilization Combined with Sisal Fiber Reinforcement for Improved Dynamic Shear Resistance and Reduced Compressibility

The geotechnical challenges associated with the dynamic shear resistance and compressibility of Berea Red Soil (BRS), a highly weathered and problematic soil, pose significant concerns for pavement structures. The conventional soil stabilization techniques often rely on non-sustainable materials, highlighting the urgent need for eco-friendly alternatives that enhance soil performance while minimizing environmental impacts. This study investigates the use of biopolymer stabilization in combination with sisal fibre reinforcement as a sustainable method to improve the dynamic shear resistance and reduce the compressibility of Berea Red Soil. The research aims to evaluate these materials' mechanical behaviour and suitability under dynamic loading conditions. Oedometer and dynamic shear tests were conducted to analyze the effects of varying biopolymer concentrations and fibre contents on the BRS geotechnical properties. Comparative analyses were carried out to assess the improvements achieved with biopolymer and fibre treatments. The findings revealed significant enhancements in the dynamic shear resistance of the treated BRS, with biopolymer concentrations and sisal fibre inclusions contribute to improved cohesion and interparticle bonding up to 86% compared to untreated BRS. Compressibility tests demonstrated a notable increase in Coefficient of Compressibility values under loading, validating the effectiveness of the biopolymer and sisal fibre inclusions. The integration of biopolymers and sisal fibres offers a promising, sustainable alternative for the stabilization of BRS. This method addresses the soil's geotechnical deficiencies and reveals an excellent proportionality between time void ratio and shear modulud, which fosters a stronger bonding between the soil matrix and sisal fibre.