Advanced 3-D Seismic Soil-Structure Interaction Analysis of a Cellular-Raft Foundation in Soft Clay

Seismic soil-structure interaction performance evaluations of projects located in deep soft clay deposits warrant special attention, particularly when designing strategic infrastructure that must remain operating after a major earthquake. The development of numerical analytical platforms in recent decades, along with faster computing tools, have made possible to include in the state of practice quite sophisticated solution techniques aimed at better representing the physics of the problem at hand. This paper presents the application of a 3-D finite difference model for evaluating the static and dynamic response of a 118 by 100 m cellular-raft foundation to be built in soft clay. The raft foundation is a 2.5 m high box-type foundation embedded 1 m and supported by a grid of peripheral and internal walls, 2.5 m long and 0.40 m thick, which integrates a cellular structure. The model is used to obtain first the static behavior exhibited by the foundation for the construction stages, including long term consolidation, and then the design earthquake is considered and the equation of motion is solved in time domain.