Innovative geotechnical solution for base isolation

Abstract

Base isolation systems have been widely recognized as a promising solution for mitigating seismic hazards in buildings. This paper explores a novel solution to the problem of earthquake damage to low-rise buildings in developing countries, where traditional base isolation systems are often too costly and difficult to install. The proposed solution is a Geotechnical Seismic Isolation (GSI) system composed of geomaterials beneath the building foundation to act as a seismic filter medium, reducing the intensity of seismic waves by energy dissipation and damping. The present study focuses on using the Sand-rubber mixture (SRM) and geogrid composite as the geomaterials for energy dissipation. The study includes laboratory tests to optimize the geomaterial composition, scaled model tests, and finite element-based numerical studies to assess the performance of the GSI system under static and dynamic loading. It was observed from the element test that SRM with 30% rubber content has adequate shear strength and damping properties to be used as a foundation bed. The results from scaled model tests on a model footing placed on the GSI system show that a geogrid-reinforced GSI layer can increase bearing capacity up to three times with a significant reduction in settlement. Based on finite element studies on a symmetric low-rise framed building placed on the proposed GSI system subjected to seismic excitation, it was found that GSI is effective in reducing peak ground acceleration and decreasing the shear force and interstory drift in the building.