Efficacy Assessment of Helical Piles in Mitigating Liquefaction-Induced Shallow Foundation Settlements using Large-Scale Shake Table Tests-PPT Presentation

PPT Presentation

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This presentation reports large-scale shake-table tests evaluating helical piles as a way to reduce liquefaction-induced settlement of shallow foundations. The research responds to earthquake damage in which shallow-founded buildings settled significantly, while deep-founded structures generally performed better.<br /><br />Two test series were conducted at UCSD’s Powell Laboratory: a baseline test without mitigation and a mitigation test using a group of 22 helical piles. Each model included a shallow foundation above a liquefiable sand layer with a shallow groundwater table and an overlying crust. Both tests involved strong shaking and produced extensive liquefaction and sand ejecta.<br /><br />The results showed a substantial reduction in foundation settlement with helical piles: approximately 28 cm (11 in.) in the baseline test compared with 1.2 cm (0.5 in.) in the mitigation test. The piles showed no observed damage or plastic deformation. The tests also reproduced settlement mechanisms associated with shaking, transient hydraulic gradients, ejecta, and soil volume changes.<br /><br />The researchers conclude that helical piles performed effectively in these tests and may offer a cost-effective mitigation approach for buildings on shallow foundations in liquefiable soils. The work demonstrates the value of large-scale physical testing and collaborative research, while supporting further investigation of seismic resilience for residential structures.

Keywords

helical piles

liquefaction

shallow foundations

settlement mitigation

shake-table tests

earthquake engineering

UCSD Powell Laboratory

seismic resilience

sand ejecta

foundation damage