Modelling installation of helical anchors in clay

Abstract

Helical anchors, which are mostly used to resist uplift, are deep foundations installed by rotation into the ground. Despite the central role of the installation process, especially with respect to the effect of soil disturbance, relatively little is known about the forces and deformations occurring during installation. An exception is the field verification technique known as torque-capacity correlation, which attempts to relate installation torque directly to uplift capacity. However, there are open questions regarding this approach, since not all significant parameters, such as installation vertical force and helix pitch, are taken into consideration. This could be one of the main reasons behind the wide range of torque-correlation factors reported in the literature. This study presents a three-dimensional numerical analysis of the installation process for helical anchors in clay. The results are synthesised into convenient yield envelopes that predict the relationship between installation torque and normal force as functions of helix pitch, roughness, and thickness. The application of the findings to torque-capacity correlation is also discussed. © 2015 Taylor & Francis Group, London.