Compared analysis of settlements for deep and shallow foundations with groundwater fluctuation using centrifuge tests

In this study, the effects of groundwater level (GWL) fluctuation on settlements of footing and pile in sand were investigated based on results from the centrifuge tests. The effect of GWL fluctuation was significant yet different depending on the type of foundation. Settlements induced by GWL fluctuation were 7.06% (141.2 mm) and 9.13% (27.4 mm) of footing width and pile diameter, respectively, indicating that pile was less sensitive to GWL fluctuation. Settlements of both footing and pile were larger during rising GWL than during falling GWL. With an increase in load level, GWL-induced settlement additionally occurred for both footing and pile. From the particle image velocimetry method (PIV), it was shown that the effect of GWL fluctuation was more significant in a zone with higher load. The load transfer relationship of pile before and after GWL fluctuation revealed that the skin friction increased in the middle part of pile and decreased in the near-surface and lower near-pile tip zones. The FE analysis was performed, and the extended lower-bound (ELB) curves of footing and pile were proposed based on the settlement ratio to quantitatively characterize the effect of GWL fluctuation.