The Uplift Capacity of Helix Anchors in Sand

Results of field and laboratory investigations of the uplift capacity of helix anchors in sand are presented. Equipment and instrumentation were used to measure uplift load, anchor deflection and sand surface deflections. Instrumentation was also used in the laboratory tests to monitor movements within the soil mass during uplift loading. The experimental results indicate that a cylindrical soil failure surface develops below the top helical shaped plate during pullout. Above the top plate the failure surface is dependent on depth of anchor embedment. Anchor installation and soil relative density also influence failure surface development. A method for estimating uplift capacity based on results of laboratory study and generally accepted soil mechanics principles is presented.