Geofoam integrated separation layer for enhancing seismic resilience in modified piled raft foundations

Abstract

Modified Piled Raft (MPR) foundations have the potential to reduce seismic force transmission to the superstructure compared to connected piled raft foundations. However, the responses of the separation layer in improving the seismic resilience of the structure were not extensively parameterized before. To address this gap, the investigation explores the potential for enhancing the seismic resilience of MPR foundations in seismically active regions by integrating sustainable materials in the separation layer between the raft and pile group. A novel separation layer is proposed by integrating geofoams with different types of soils. The performance of this novel separation layer is explored through a comprehensive 3D finite element analysis under both static and dynamic loading conditions. Using the OpenSees software platform, an extensive numerical analysis was undertaken to examine the influence of various key parameters on the system's behaviour. A comprehensive analysis of these parameters was conducted to evaluate the responses of MPR foundations with and without geofoam in the separation layer, specifically in the context of ground motion analysis. Raft thickness, pile configuration, separation layer thickness, and the materials used in the separation layer were all considered. The findings indicate that raft thickness and pile length are crucial influencing factors on the dynamic response of the MPR system. Furthermore, the inclusion of EPS geofoam in the separation layer demonstrated its effectiveness in reducing the acceleration amplitude at the top of the raft by 44.25% and lateral displacement by 47.84%, effectively mitigating the impact of seismic waves reaching the upper surface of the raft. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2024.