Assessing single-helix screw pile geometry on offshore installation and axial capacity

Abstract

Due to their low-noise installation and relatively large axial capacity, screw piles have been proposed as an alternative foundation solution in dense sand for offshore renewable energy applications in deeper water. For this to occur, a significant upscaling of onshore dimensions is required. Furthermore, the effects of certain geometric features on installation requirements are still not well understood. In this paper, the effects of base geometry, shaft diameter and helix pitch were investigated using the three-dimensional discrete-element method by simulating the full installation process prior to conducting axial compression and tension tests. The results of the investigation showed it is possible to optimise the geometry of the screw pile to reduce installation requirements, in terms of both vertical installation force (up to 61%) and installation torque (up to 39%), without reducing the axial capacity of the pile significantly.

Optimised screw pile design for offshore jacket foundations in medium–dense sand

“…The prediction of pile axial capacity is depicted in Figure 5 (Cerfontaine et al, 2021b) or loading (Sharif et al, 2021b(Sharif et al, , 2021a of screw piles can be used to enrich experimental findings and develop physically-based prediction methods. Finally, installation in the field will be undertaken at constant vertical force (pile and tool weight), with the AR adapting to maintain the vertical equilibrium.…”

Installation Disturbance of Helical Anchor in Dense Sand and the Effect on Uplift Capacity Based on Discrete Element Method

“…Extensive experiments [8,13,[21][22][23][24][25][26][27][28][29][30], numerical analyses [12,[31][32][33][34][35][36][37], and theoretical analyses [38][39][40] have been conducted on the load-bearing performance of helix anchors. Tsuha et al [28] performed centrifuge uplift loading tests on 12 different types of piles installed in two sands with different densities to examine the effect of the number of helices on the performance of helical anchors in sand.…”

“…Cerfontine et al [41] used the finite element method to predict the full tensile load-displacement response of shallow helix anchors installed in sand for practical use, incorporating the effects of a pitch-matched installation, and found the compression (crowd) load applied during the anchor installation phase modified the stress field around the anchor, which in turn affected the anchor uplift stiffness. The DEM has also been used to investigate the installation effects of helical anchors [31][32][33]. Cerfontine et al [31] found that when a single-helix pile is installed at AR < 1, the soil particles below the helical plate show an upward movement trend.…”

“…Cerfontine et al [31] found that when a single-helix pile is installed at AR < 1, the soil particles below the helical plate show an upward movement trend. Sharif et al [32,33] investigated the effects of the base geometry, shaft diameter, and helix pitch of single-helix anchors by simulating the full installation process prior to conducting axial compression and tension tests and proposed the possible optimization of the geometry of the screw pile to reduce installation requirements.…”

“…The behavior of granular material can be simulated by investigating the movement of the discrete assemblies [41][42][43][44]. However, existing research on pile installation effects based on the DEM has focused on complex screw piles (augers) [18] and single-helical piles at a certain depth [31][32][33]. The installation effects of multi-helix anchors and single-helix anchors at different embedment depths on particle displacement and uplift capacity are still unclear.…”