An investigation about seismic behavior of piled raft foundation for oil storage tanks using centrifuge modelling

Some level of settlement is allowed in the design of oil tank if the uneven settlement can be controlled in an allowable value. Considering a critical condition of piled raft foundation (PRF), that is, secure contact of raft base to the ground surface, and the expected function of piles to impose additional resistance against the local settlement, PRF is considered as one of the rational foundation systems for the oil tanks. However, PRF has a complex interaction with soil under horizontal seismic loading, especially if the tank rests on a liquefiable soil, which may cause an extreme change of the soil stiffness underneath the tank. In this study, a series of centrifuge model tests was performed to investigate the mechanical behavior of oil tank supported by piled raft foundation on liquefiable saturated sand and non-liquefiable dry sand. In the tests, two types of foundation were modelled; a slab foundation, and a piled raft foundation. Using the observed results, such as accelerations of the tank and ground, dynamic and permanent displacement of the foundation, and excess pore water pressures of the ground, advantages and limitations of piled raft foundation for application to oil tanks on sandy soil are discussed.