Effects of Multipropped Excavation on an Adjacent Floating Pile

Abstract

Deep excavations inevitably induce stress relief and soil movement, which may affect the safety and serviceability of nearby existing pile foundations. Although the effects of excavation on adjacent piles have been studied, excavation-induced pile settlement and change of shaft resistance deserve more investigation. In this paper, centrifuge simulation of the effects of multipropped excavation in-flight on vertically loaded floating piles in sand is reported. Piles were restrained in terms of rotation and lateral deflection at or above ground-surface level in three different tests. In addition, three-dimensional numerical analyses using an advanced soil model were carried out to back analyze the centrifuge tests. A pile-raft settled a similar amount due to excavation as a free-head pile and an elevated pile group. During excavation, a downward load-transfer mechanism in the piles can be identified. Shaft resistance in the upper part of the pile decreases due to the downward soil movement and the reduction of normal stress acting on the pile. In order to maintain vertical equilibrium, the pile has to settle to mobilize higher shaft resistance in the lower part of the pile and toe resistance. Lateral restraints imposed on the pile head have a significant influence on induced pile bending moment. Induced bending moment due to excavation can exceed the pile bending capacity.