Some level of settlement is allowed in the design of oil tanks if uneven settlement is controlled within allowable values. Considering the critical condition of piled raft foundation (PRF), that is, secure contact of raft base to the ground surface, PRF is considered one of the rational foundations 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. On the other hand, the pile installation method can affect the pile bearing capacity and the liquefaction resistance of sand as well. In this study, a series of centrifuge tests was performed to investigate the mechanical behavior of oil tanks supported by PRF on liquefiable sand. In the tests, slab and piled-raft foundations were modeled. In the case of PRF, two different methods of pile installation (Driven and NonDriven) were modeled and the Driven PRF models were made with two different pile numbers. Using the observed results, such as accelerations of the tank and ground, displacements of the foundation and excess pore water pressures of the ground, advantages, and limitations of PRF for oil tanks on liquefiable sand are discussed.
Recent huge earthquakes have caused severe and small damage to a number of geogrid-reinforced soil walls. For proper repair or reconstruction, it is necessary to evaluate degree of damage of those structures. In this research, the pullout test of geogrid subjected to the unloading-reloading process was carried out to learn its effects on the pullout resistance. The results were then used to evaluate the factor of safety and sliding surface of the damaged geogrid reinforced soil wall. GRSW models in centrifuge shaking and tilting table tests under 50G were performed. The damaged GRSW models were first achieved by both shaking and tilting. The damaged GRSW were then subjected to unloading-reloading process until the full collapse occurred. The pullout peak value and residual value using in current design of GRSW were also discussed.
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