Investigation of installation stress level on the vertical and lateral loading behaviour of open-ended piles by centrifuge tests

Abstract

Extensive research has focused on quantifying the loading behaviour of 1g (g, gravitational acceleration rate) installed open-ended piles using centrifuges. However, the influence of installation stress level on loading behaviour is often ignored, with ramifications for the accuracy and validity of results. In this paper, a loading apparatus is developed to allow in-flight jacking of piles followed directly by vertical or lateral loading, without needing to stop the centrifuge, which facilitates maintaining the installation-related stress state. Model piles are installed at 50g and 1g, and the vertical and lateral responses are analyzed. The effect of pile installation stress level on the initial stiffness, resistance, and soil plug behaviour, is investigated. Results indicate that installation stress level has a more significant and non-uniform effect on pile vertical behaviour than lateral behaviour. Piles that are not fully installed at 50g can mobilize the same vertical resistance as those fully installed at 50g, provided they experience a minimum of 2D (D, pile diameter) in-flight installation length. The arching effect caused by soil plugging, and the denser sand state surrounding the pile toe, may provide higher vertical and lateral resistance for piles installed at 50g compared to those installed at 1g.