Stress transfer mechanisms and settlement of a floating pile due to adjacent multi-propped deep excavation in dry sand

Abstract

Three-dimensional numerical parametric study is conducted to investigate stress transfer mechanisms and settlement of a floating pile due to multi-propped basement excavation by using hypoplastic sand model. Centrifuge test results are adopted to validate the soil model and model parameters. Effects of excavation depth, pile location with respect to basement, working load, sand density and support system stiffness are examined. Downward and upward load transfer mechanisms are observed at different excavation stages, depending on the ratio of excavation depth (He) to pile length (Lp). If excavation-induced reduction of shaft and base resistances are ignored, the pile settlement is underestimated by up to 39%. Negligible pile head settlements are observed when the pile is located at a distance exceeding 2.5 He (excavation depth) from the retaining wall. Basement excavation-induced pile settlement is doubled when the designed factor of safety of pile before excavation reduces from 3.0 to 1.5. By increasing the relative sand density 30–90%, the pile settlement decreases by up to 66%. Excavation-induced pile head settlement is almost insensitive to support system stiffness for shallow excavation (He/Lp < 0.4).