Investigation of Geotechnical Seismic Isolation Bed in Horizontal Vibration Mitigation

Recently, a ground-borne vibration mitigation solution using rigid wave impeding blocks embedded in the foundation bed of buildings/embankments has emerged as a passive vibration isolation mechanism, wherein energy dissipation due to material damping was often ignored. The present study aims to examine the performance of a flexible foundation bed composed of a sand-rubber mixture (SRM) for ground-borne vibration isolation, referred to as geotechnical seismic isolation (GSI) bed, an emerging trend in low-cost earthquake mitigation studies. Field investigation consisting of vibration measurement on a model footing resting on a GSI bed with SRM and SRM-geogrid composite subjected to horizontal sinusoidal vibration of frequency 10 to 30 Hz with acceleration amplitude of 0.18 g to 0.33 g were undertaken. Further, a three-dimensional finite-element analysis of a model footing resting on a GSI bed made of geogrid reinforced SRM composite is presented. The strain-dependent nonlinear response of soil and SRM were accounted for using suitable hypoelastic and hyperelastic constitutive formulations, respectively. For the GSI bed, SRM with 10% to 50% rubber content and biaxial geogrids were studied. The numerical simulation and field study results were found to be comparable with a nominal difference that verifies the adequacy of the developed numerical modeling procedure. It was observed that GSI (30% rubber content) effectively reduced the vibration acceleration amplitude of the model footing above 40% and 55% for without and with geogrid reinforcement, respectively. Overall, the field experimental and numerical results demonstrate the proposed geogrid reinforced GSI bed as an effective ground vibration mitigation solution for typical industrial environments.