Jetted helical anchor installation as a torque reducing technique

Helical piles and anchors are being increasingly considered for offshore renewable energy applications. However, the very high installation torque required at the scales relevant to offshore use remains a significant barrier to their deployment. This paper investigates a torque-reduction strategy based on water jetting around the helix during installation, which generates excess pore pressure, reduces effective stress and consequently lowers the required installation torque. A series of model scale centrifuge experiments in dense sand examines the influence of jetting flow rate, nozzle configuration, helix size and embedment depth on both the required installation torque and the subsequent uplift capacity. The results demonstrate that jetting leads to a substantial reduction in installation torque, enabling significantly greater embedment depths, larger helix diameters, or a combination of both. While jetting results in a modest reduction in tensile capacity, this effect is more than offset by the much higher capacity achievable through deeper installation under reduced torque demand.