Full-Scale Testing of Gravel-Rubber Trenches for Geotechnical Seismic Isolation

This paper presents preliminary findings from a full-scale experimental investigation into the use of gravel-rubber mixture (GRm) trenches as a Geotechnical Seismic Isolation (GSI) strategy. While trench-based wave barriers have been widely studied for high-frequency vibration screening, their application to low-frequency earthquake-induced ground motions remains largely unexplored at full scale. The study was conducted at the EuroSeistest facility (Thessaloniki, Greece) using the EuroProteas structure, where harmonic forced-vibration tests were performed within the frequency range of 2 to 5 Hz. The response of the system was evaluated under natural soil conditions and compared with GRm vertical trench configurations containing 50% and 100% rubber by volume. The results show that both configurations consistently reduce motion transmitted from the soil to the foundation, with attenuation becoming more pronounced at higher excitation frequencies and within the range where soil-structure interaction effects are most significant. These findings provide full-scale experimental evidence that GRm trenches attenuate low-frequency seismic motions, supporting their potential as a practical GSI solution for retrofit of existing infrastructure.