Vertical Uplift Capacity of a Group of Helical Screw Anchors in Sand

Abstract

In this paper experimental investigations on the behavior of single, double and triple helical screw anchors under the influence of vertical uplift loads are presented. The testing program was conducted on three model anchors having single, double and triple helical screws installed in sand. The experimental setup was instrumented to measure the pullout load and the upward displacement of the anchor. It was observed that the pullout load varied significantly with the installation depth of the anchor and the number of anchors. A mathematical model was developed using the limit-equilibrium method of analysis. Based on experimental results, non-dimensional graphs were plotted normalizing the deformation and load axis both and simple equations are proposed correlating load and deformation. Using these equations an anchor foundation for a particular structure can be designed. Comparison of the pullout load values obtained from the theory developed and the present experimental results showed good agreement. © 2013 Indian Geotechnical Society.