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

PPT Presentation

Pdf Summary

The study evaluated helical piles as a mitigation measure for earthquake-induced settlement of shallow foundations on liquefiable soils. Motivated by severe damage to buildings during past earthquakes, the researchers conducted two large-scale shake-table test series at UCSD: a baseline test without mitigation and a test using a group of 22 helical piles.<br /><br />The model included an isolated footing over a uniform liquefiable sand layer with a shallow groundwater table and a non-liquefiable surface crust. Both series involved multiple shakings and extensive instrumentation to measure soil and foundation response. The experiments reproduced liquefaction, excess pore-water pressure, and sand ejecta.<br /><br />The key result was a substantial reduction in foundation settlement with helical piles: the baseline foundation settled 28 cm (11 inches), compared with 1.2 cm (0.5 inches) in the mitigation test. The piles showed no observed damage or plastic deformation. The tests also demonstrated that large-scale 1-g shake-table experiments can reproduce important behaviors of shallow foundations on liquefiable soils.<br /><br />The researchers concluded that helical piles performed well as a settlement-reduction strategy in these tests. Further data interpretation was planned, and the baseline results were intended for publication.

Keywords

helical piles

earthquake-induced settlement

liquefiable soils

shallow foundations

shake-table tests

liquefaction

excess pore-water pressure

foundation mitigation

UCSD experiment

soil settlement