Locked-In Stresses Matter: the Effect of Installation and Centrifuge Spin-Down on Helical Anchor Performance in Sand

Publication Title
Locked-In Stresses Matter: the Effect of Installation and Centrifuge Spin-Down on Helical Anchor Performance in Sand

Abstract

Geotechnical centrifuge modelling offers a cost-effective, high-fidelity means of investigating geotechnical processes, from foundation installation through to in-service loading. Foundation installation alters the stress state in the soil, and while preserving installation-induced stress history is crucial for reliable interpretation, the technical challenges of performing both installation and loading within a single centrifuge flight often leads to modelling compromises, with the centrifuge stopped between installation and loading. This study investigates how a centrifuge spin down/up cycle between installation and loading influences the behaviour of helical anchors in dense saturated sand, aiming to clarify whether continuous in-flight modelling is essential to accurately represent the performance of helical anchors. Two anchor tests were performed under different conditions: (i) in-flight anchor installation under constant weight followed by anchor extraction (ii) in-flight constant weight anchor installation followed by a spin down/up cycle before anchor extraction. The anchor installed and loaded in-flight without stopping the centrifuge gave a higher capacity (by more than 30%) and a markedly stiffer loaddisplacement response compared to the test involving a spin down/up cycle, suggesting that post-installation stress relaxation has a sufficient influence on anchor behaviour to warrant maintaining in-flight conditions throughout installation and loading. Any interruption may release locked-in stresses and lead to significant underestimation of anchor strength and stiffness.

Authors
A. Juliano Nietiedt; Phil Watson; Conleth O'loughlin; Christophe Gaudin

Published In

11th International Conference on Physical Modelling in Geotechnics (ICPMG2026)

Theme

Special Session 4: Innovative Methods for Offshore Foundation Installation