Shaft friction changes for cyclically loaded displacement piles: an X-ray investigation

J Doreau-Malioche,G Viggiani,J B Toni,G Combe

doi:10.1680/jgele.17.00141

Abstract

The mechanisms occurring at the grain scale at sand–pile interface under axial cyclic loading are analysed quantitatively in a mini calibration chamber, using X-ray tomography and three-dimensional-digital image correlation. Grain kinematics and porosity evolution are followed along with the macroscopic mechanical response of the interface. The results show different phases in the evolution of shaft resistance during cyclic loading, with a non-negligible increase of shaft resistance in the latter phase. The test conditions are not representative of real engineering applications, where piles supporting bridges, tidal or wind turbines have to safely sustain severe load-controlled cycles. However, advanced image analysis sheds light on the mechanisms controlling the macroscopic behaviour of sand–pile interface. This study provides valuable data set against which theoretical or numerical approaches can be tested.

Highlights

The mechanisms controlling the macroscopic behaviour of sand–pile interface during pile installation and cyclic loading are complex and are difficult to fully understand from field observations
Typical results from 3D-digital image correlation (DIC) are presented in Fig. 5
The influence of axial cyclic loading on the behaviour of sand–pile interface has been analysed at the grain scale thanks to X-ray tomography and advanced 3D image analysis

Summary

Introduction

The mechanisms controlling the macroscopic behaviour of sand–pile interface during pile installation and cyclic loading are complex and are difficult to fully understand from field observations. Jardine & Standing (2000, 2012) reported results of multiple axial cyclic loading tests conducted on steel open-ended pipe piles driven in sand, at Dunkerque, northern France. INTRODUCTION The mechanisms controlling the macroscopic behaviour of sand–pile interface during pile installation and cyclic loading are complex and are difficult to fully understand from field observations. This work focuses on the sand grains behaviour in the vicinity of a pile during axial cyclic loading.

Results

Conclusion