Effects of construction sequence of double basement excavations on an existing floating pile

Deep excavations inevitably induce stress relief and ground movement, which may affect the safety and serviceability of nearby pile foundations. Although research attention was paid to the basement-soil-pile interaction, most of the previous studies focused on responses of end-bearing piles due to a single basement excavation. In this study, centrifuge tests and numerical analyses were conducted to investigate effects of construction sequence of double basement excavations on an existing floating pile in dry sand. For basements excavated sequentially (i.e., multi-propped excavation is conducted before cantilever excavation), the measured pile settlements due to multi-propped and cantilever excavations are 0.42% dp and 0.72% dp (pile diameter), respectively. This is because multi-propped excavation causes a reduction of soil shear modulus, and cantilever basement has much smaller support system stiffness than multi-propped basement. The horizontal soil movement and pile bending moment due to multi-propped excavation are reversed during cantilever excavation. Upon completion of double basement excavations, construction sequence of double basements (i.e., excavated sequentially and simultaneously) has limited effects on pile head settlement. But the maximum bending moment due to double basements excavated simultaneously is only 18.9% of that due to double basements excavated sequentially. To ensure the safety and serviceability of existing pile foundation, it is suggested to construct double basements simultaneously rather than sequentially.