Helical pile installation for offshore renewable energy exploration in clay seabed

Offshore wind and wave energy exploration are moving from shallow waters with fixed foundations to deep waters with floating devices. Helical pile has the potential to be used as both shallow water foundations and deep water anchors due to its ‘quiet’ installation and environmental friendliness to marine living systems. Although helical pile and/or anchor have been used extensively for onshore applications, their offshore applications need larger diameters and longer shaft than the onshore counterparts hence pose significant installation challenges. This paper presents the current studies on helical pile installation process in clay seabed. The installation of helical pile in uniform and normally consolidated clay have been studied physically in centrifuge and numerically using large deformation finite element (LDFE) analyses. Both installation torque and installation force (or crown force) were studied under different pile-soil friction coefficients and different helical pile advancement ratios (AR: ratio of pile penetration to helix pitch). Soil flow mechanisms under different ARs can explain the development of required toque and crown force during torsional pile installation. The installation torque and installation force are a function of AR and can be designed based on the capacity of installation equipment.