Centrifuge Investigation of Groundwater-Induced Footing Settlement in Sand Considering Rising and Falling GWL Phases

In this study, the effect of fluctuating groundwater level (GWL) on the settlement of footing foundation placed on sand was investigated based on the results obtained from centrifuge tests. In the tests, rising and falling phases of GWL were both considered, and the values of footing settlement (sft) obtained from each phase were compared. The centrifuge testing program was designed with a specifically manufactured test box and hydraulic control system. Image-based particle-displacement analysis using particle image velocimetry (PIV) was performed to capture inner soil particle movement during GWL fluctuation. Ground subsidence occurred most significantly during the first GWL fluctuation. Fluctuating GWL caused considerable sft while load was unchanged. sft was larger for rising GWL than for the falling phase and decreased as the number of GWL fluctuation increased. PIV analysis indicated that GWL-induced settlement was not uniform but larger within higher-loaded zone below footing, even if GWL changed uniformly and load on footing was unchanged. The collapse potential was introduced to describe and explain GWL-induced footing settlement, which was consistent with the results observed from the centrifuge tests.