Uplift Behavior of Screw Anchors in Sand. I: Dry Sand

Abstract

Experimental and theoretical investigations on the behavior of single‐screw helical anchors in sand are presented. A testing program included 56 tests conducted on five model anchors installed in dense, medium, and loose dry sands. A sand‐placing technique was developed and utilized over the testing program in order to achieve the predetermined unit weight. The experimental setup was instrumented to allow the measurement of the pullout load, the upward displacement of the anchor, and the deflection of the sand surface. It was observed that the failure mechanism as well as the pullout load varied with the installation depth of the anchor and the angle of shearing resistance of the sand. A mathematical model is developed using the limit‐equilibrium method of analysis and the observed failure mechanism of the anchor from the present experimental work. Based on experimental results, a simple equation is proposed to introduce the degree of shear mobilization on the coefficient of passive earth pressure. Comparison of the theory developed and experimental results of the present investigation as well as experimental field results reported in the literature showed good agreement.