A study of the dynamic soil-structure interaction of deep shafts constructed in dense sand ground

Abstract

The design of the deep shafts is generally considered to be in a weak soil against liquefaction, however the shafts which are built as a facility in nuclear power plants, are mainly built-in dense ground. In this study, we aimed to clarify the interaction between the ground and the shaft during an earthquake, which is simulated in a dense sandy soil. To achieve this goal, a series of dynamic centrifuge model tests and liquefaction analysis based on effective stress analysis by using FLIP are performed. In the analysis 14.1m deep circular shaft is modelled as buried in 10.2m thick liquefiable dense sand layer, which is covered with 3.9m of non-liquefiable dense sand layer. The results of the analysis showed that the negative excess pore water pressure, the maximum acceleration, and the maximum ground displacement of the liquefiable ground occurred simultaneously. However, the time that maximum acceleration of the structure and the maximum displacement of the ground did not always coincide. In case of dense sandy soil, we observed a small ground deformation even if the excess pore water pressure increased. As a result, since the ground deformation, which generally has a large impact on the structures, was small, the earth pressure was also small. The obtained results confirmed that the shafts in dense sandy ground performed well under dynamic effects. Hence, in design by performing numerical analysis with comprehensive soil and structure properties, economical and conservative solutions can be achieved.