Seismic performance of thinner rubber-sand mixture cushion reinforced by geosynthetics

Rubber-sand mixture (RSM) has proven to be a cost-effective fill material, serving as a seismic isolation cushion between natural site soil and structure foundations. Although the isolation effect improves with increased cushion thickness, the stability of the superstructure tends to decrease while costs rise with greater thickness. Hence, it is crucial to minimize cushion thickness while attaining the optimal isolation objective. This study experimentally assesses the seismic performance of thinner RSM cushions reinforced by geosynthetics, specifically geocells, geotextiles, and geogrids. The effects of superstructure mass, cushion thickness, and excitation mode on the isolation coefficient of geosynthetic-reinforced rubber-sand mixture cushions (GRRSMC) are thoroughly evaluated. The results indicate that the isolation effect of reinforced cushions exceeds that of the unreinforced ones with the same thickness. Among the different reinforcements, geotextile provides the highest isolation efficiency, followed by geocell and geogrid. The seismic performance of GRRSMC is primarily attributed to the low shear modulus. Additionally, geosynthetic reinforcement enhances the vertical modulus, which helps to attenuate seismic waves. These findings validate GRRSMC as a viable low-cost seismic approach, ensuring superstructure stability, and reducing cushion thickness.