Abstract

In densely built areas, development of underground transportation system often involves excavations for basement construction and cut-and-cover tunnels which are sometimes inevitable to be constructed adjacent to existing piled foundations. In order to gain new insights into single pile responses (i.e. settlement and load transfer mechanism) to an adjacent excavation in saturated silty clay, a three-dimensional coupled- consolidation numerical analysis is conducted in this study. An advanced hypoplasticity (clay) constitutive model with small-strain stiffness was adopted. A linear increase in pile settlement was observed due to excavation-induced stress release. This is because part of the pile is placed within the boundaries of a major influence zone due to excavation-induced ground movement. Based on a settlement criterion, apparent loss of pile‘s capacity is 14%. A maximum bending moment of about 350 kNm is induced in the pile with the maximum deflection of 28 mm. In addition, mobilisation of shear strength at the pile-soil interface was found to be a key factor governing pile-soil-excavation interaction. During excavation, a downward load-transfer mechanism in the piles can be identified.

Highlights

  • The development of underground space induces ground movements and stress release in the surrounding soil that may affect existing structures

  • In view of the aforementioned issues, this study aims at investigating the settlement and load transfer mechanism of an existing single pile due to an adjacent excavation in saturated silty clay

  • This is because the pile was subjected to lateral soil movement towards the excavation resulting from significant stress release

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Summary

INTRODUCTION

The development of underground space induces ground movements and stress release in the surrounding soil that may affect existing structures. Authors in [10] developed design charts to compute the lateral behaviour of a single pile adjacent to deep excavation in soft ground They performed two staged analysis considering plane strain conditions and linear elastic soil model. In view of the aforementioned issues, this study aims at investigating the settlement and load transfer mechanism of an existing single pile due to an adjacent excavation in saturated silty clay. To achieve these objectives, a three-dimensional coupledconsolidation numerical modelling was carried out. Settlement, axial load distribution along the pile, stress changes and excessive pore pressure generation during excavation are reported and discussed

THREE-DIMENSIONAL COUPLED CONSOLIDATION
Constitutive Model and Model Parameters Used in Finite Element Analysis
Findings
INTERPRETATION OF COMPUTED RESULTS
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