Sustainable stabilization of soft clay using rice straw fibers: Mechanical and consolidation behavior

• Untreated rice straw fibers increased UCS of clay soil by up to 348% • Optimum mix: 1.5% fibers, 15 mm length at 60–68% moisture content • Short fibers are most effective at high WC; long fibers at low WC • Excessive fiber (>2.5%) increased soil compressibility • Eco-friendly, low-cost alternative to cement/lime stabilizers Soft clay soils exhibit low shear strength, high compressibility, and poor stability. Conventional stabilization methods rely on cement or lime, which are costly and unsustainable. This study explores untreated rice straw fibers as a sustainable stabilizer for soft clay. Fibers were added at 0–3% by dry weight (15 and 25mm lengths) under different moisture contents (54%, 60%, 68%). Tests included unconfined compressive strength (UCS), consolidation, and compaction. Results showed UCS improvement of up to 348% at optimum mix (1.5% fiber, 15 mm, 60–68% WC). Short fibers performed better at high moisture, long fibers at low moisture. Excessive content (>2.5%) increased compressibility. Compared to RHA (∼200%) and coconut coir (100–150%), untreated rice straw fibers outperformed without chemical treatment. These findings support their role as a low-cost, eco-friendly alternative to traditional stabilizers.