Centrifuge Modeling of Axial Failure of Helical Piles in Cohesive Soils-PPT Presentation

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The study developed a geotechnical centrifuge system to install, instrument, and axially load model helical piles in clay. Centrifuge testing offers a lower-cost way to investigate pile behavior where full-scale field tests are difficult or impractical, such as remote and offshore sites. The system protected shaft-mounted strain gauges during centrifuge operation and enabled measurement of axial load distributions.<br /><br />Tests examined piles under tension and compression in medium and stiff clay. The researchers assessed load transfer and observed different failure mechanisms, including cylindrical shear, individual helix bearing, and transitional failure. In medium clay, a double-helix pile with a spacing-to-diameter ratio around 2.5 exhibited transitional failure. This mechanism reduced helix resistance and could lead conventional methods to overpredict axial capacity by approximately 38–52%. The finding highlights the need for caution when designing multi-helix piles with this spacing in medium clay. Shaft adhesion was also found to be ineffective close to a helix.<br /><br />The project demonstrates that centrifuge modeling can provide useful measurements of helical pile performance and failure behavior across soil profiles, helping engineers refine design assumptions and pile geometry. The authors emphasize that the method can support more economical evaluation when field testing is challenging.

Keywords

geotechnical centrifuge

helical piles

clay soil

axial load transfer

model testing

pile capacity

tension and compression

transitional failure

double-helix pile

shaft adhesion