DFI Journal - The Journal of the Deep Foundations Institute

Volume 10, Issue 3, January 2016

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Cyclic axial performance of helical-tapered piles in sand

A. Fahmy and M. H. El Naggar


The cyclic performance of a novel piling system is presented in this article. It is composed of spun-cast ductile iron (SCDI) tapered pile fitted with a lower helix. The pile combines the durability of rough surface spun-cast ductile iron, the efficiency of tapered section and the construction advantages of helical piles. Five instrumented SCDI tapered helical piles and two straight helical piles were installed in sand and tested in cyclic compression and uplift. Effects of prior monotonic and cyclic tests on the piles’ cyclic performance were assessed. Finite element simulations of the tested piles were performed to evaluate the possible stiffness change during loading. The proposed pile exhibited enhanced cyclic compressive performance compared to straight shaft piles. Prior cyclic uplift loads had a negative effect on the proposed pile’s performance, whereas previous monotonic compression loading reduced its cyclic uplift displacement. Both tested configurations showed satisfactory cyclic uplift performance when tested following monotonic uplift.