Influence of rubber content and particle morphology on the dynamic behaviour, liquefaction susceptibility and internal stability of shredded rubber-sand mixtures

Understanding the resilience of Rubber-Soil mixtures (RSm) under cyclic loading is crucial for their application in seismic isolation. This study presents an investigation into the dynamic behaviour, internal stability, and liquefaction resistance of Shredded Rubber Sand mixtures (ShRSm) under both short and long-term loading conditions. Key material properties including rubber content, size ratio, and particle shape were compared with existing literature. Utilising resonant column and cyclic triaxial apparatus, an experimental programme was conducted across small to large strain amplitudes, applying up to 400 strain-controlled cycles. The findings reveal that mixtures with larger or elongated rubber particles exhibit greater stiffness degradation but also higher damping capacity. Incorporating 10% to 20% Shredded Rubber (ShR) by mass significantly enhances internal stability, reduces stiffness degradation under strains up to 1%, and mitigates pore water pressure buildup, thereby improving liquefaction resistance. While sand-like soils display higher initial energy dissipation that decays under loading, rubber-like soils maintain consistent damping over long-term cyclic conditions. These results not only advance the understanding of RSm in seismic applications but also demonstrate that ShRSm is a viable and sustainable material for permanent Geotechnical Seismic Isolation (GSI) technology, with the potential to influence engineering practices in earthquake-prone regions.