Helical piles: an innovative foundation design option for offshore wind turbines

Abstract

Offshore wind turbines play a key part in the renewable energy strategy in the UK and Europe as well as in other parts of the world (for example, China). The majority of current developments, certainly in UK waters, have taken place in relatively shallow water and close to shore. This limits the scale of the engineering to relatively simple structures, such as those using monopile foundations, and these have been the most common design to date, in UK waters. However, as larger turbines are designed, or they are placed in deeper water, it will be necessary to use multi-footing structures such as tripods or jackets. For these designs, the tension on the upwind footing becomes the critical design condition. Driven pile foundations could be used, as could suctioninstalled foundations. However, in this paper, we present another concept-the use of helical pile foundations. These foundations are routinely applied onshore where large tension capacities are required. However, for use offshore, a significant upscaling of the technology will be needed, particularly of the equipment required for installation of the piles. A clear understanding of the relevant geotechnical engineering will be needed if this upscaling is to be successful.

Cone Penetration Testing IV

“…The magnitude of the installation torque (T) of onshore piles is typically used in the verification of the axial tensile capacity (Q t ) through the empirical factor, K t , developed by Hoyt and Clemence (1989), given in equation 1. Byrne and Houlsby (2015) have developed this further with the use of a dimensionless torque factor. However, BS 8004:2015(British Standards Institution, 2015 states that screw piles should not be designed solely using empirical methods.…”

“…It is these benefits, offered by screw piles, which have led some authors (Byrne andHoulsby, 2015, Spagnoli andGavin, 2015) to suggest their use in the offshore environment, as foundations for deep water offshore wind energy projects.…”

New perspectives in offshore wind energy

“…In the theme issue, the papers by Kallehave et al [40], Byrne & Houlsby [41], McGugan et al [42], and Borg & Collu [43] are dedicated to these subjects.…”

“…Byrne & Houlsby [41] provide a further insight into foundations design and installation. The authors propose helical piles as an innovative foundation concept for multi-footing substructures in transitional waters, such as tripods and jackets, discussing the advantages over driven piles used in conventional design.…”

Effects of vertical loading on lateral screw pile performance

“…This pile is of reduced dimensions to that considered in this study and suggests the potential for significant increase in torque requirements. Byrne and Houlsby (2015) suggest that the ratio V t,ult D h /T may typically be of the order of 8 (where T is the torque applied during installation). Thus, for a screw pile with a tensile capacity of 11 MN (the largest pile simulated here), a torque of 3·4 MN.m would be required for installation.…”