Centrifuge modelling of the installation and uplift of helical anchors in clay

This study investigates the installation and uplift behaviour of helical anchors in clay through 14 centrifuge tests at 80g. For each test, the helical anchor was installed at a specified advancement ratio (AR), defined as the ratio of vertical penetration per revolution to helix pitch, and was then subjected to either immediate uplift or uplift after full consolidation. The test results show that the required vertical force decreased with reducing AR, and the helical anchor was under tension for AR ≤0·75. The required torque increased by 137·5% as AR reduced from 3 to 0·5, then fell slightly at lower ARs. The immediate holding capacity exhibits a maximum value at AR = 0·9, whereas the consolidated holding capacity increases with AR because of greater post-consolidation strength gain. Excess pore pressures above and below the helix were monitored. Installation consistently generated positive excess pore pressure above the helix, peaking at AR = 0·9, while the pore pressure beneath the helix diminished with reducing AR. During uplift, the difference between the excess pore pressures above and below the helix closely correlated with the uplift resistance. The findings provide guidance for the design of helical anchors and optimisation of installation equipment.