Large-Scale Shake Table Experiment on the Performance of Helical Piles in Liquefiable Soils-Paper

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The study evaluated helical piles as a means of reducing liquefaction-induced settlement of shallow foundations. Researchers conducted two large-scale shake-table experiments at the University of California, San Diego: an unmitigated baseline test and a test in which four single-helix piles connected the foundation to a dense soil layer beneath liquefiable sand. Both models used comparable three-layer soil profiles and were subjected to strong shaking; the paper reports results from the first shaking sequence.<br /><br />The helical-pile test showed substantially improved foundation performance. Average settlement fell from 28 cm in the baseline test to 1.2 cm—a reduction of approximately 96%. In-plane and out-of-plane differential settlements, as well as foundation tilt, were also greatly reduced. Excess pore-water pressure generally developed more slowly and reached lower levels in the pile-supported model, likely partly because installation densified the surrounding soil. The piles transferred foundation loads to the underlying dense layer, limiting settlement associated with several liquefaction mechanisms. No visible pile deformation was observed after testing.<br /><br />The findings indicate that helical piles can effectively protect shallow foundations from liquefaction-related settlement under the tested conditions, including in situations where underpinning access or headroom may be limited. The authors identify them as a potentially cost-effective mitigation option, although the experiments assessed performance rather than comparing actual project costs.

Keywords

helical piles

liquefaction

shallow foundations

settlement reduction

shake-table experiments

excess pore-water pressure

foundation tilt

soil densification

dense soil layer

seismic mitigation