Research on long-term settlement characteristics of soft soil foundations in reclamation sites based on field monitoring and centrifugal tests

Based on typical stratigraphic conditions of a land reclamation project, this study combines field monitoring with centrifuge model tests to investigate the long-term settlement characteristics of deep soft foundations after surcharge preloading. Field monitoring, conducted over approximately five years following the completion of preloading, indicates that the combined use of plastic vertical drains and surcharge preloading effectively controls post-construction ground settlement, with the growth rate of total settlement gradually decreasing over time. In areas with shallower soft soil layers, the monitored settlement ranges from approximately 90-350 mm, with the settlement rate reducing to 0.01 mm/d. In contrast, in areas with thicker soft soil layers and underlying weak strata, settlement reaches 260-430 mm, and the settlement rate remains above 0.1 mm/d. Centrifuge tests are employed to simulate the entire process of foundation settlement under surcharge preloading, and the settlement development over 50 years after construction is predicted. Both experimental and monitoring results demonstrate that whether the vertical drains fully penetrate the entire soft soil layer is critical for long-term settlement control. Full penetration significantly enhances settlement control during foundation treatment and effectively suppresses post-construction settlement. Incomplete penetration, however, leads to slow drainage in the lower soft soil layer, resulting in prolonged deformation and significant post-construction settlement. The research findings provide experimental evidence and references for the design and construction of similar land reclamation projects.