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A review of a CPT based axial capacity prediction of screw piles in sand
Published in Guido Gottardi, Laura Tonni, Cone Penetration Testing 2022, 2022
E.J. Bittar, B.M. Lehane, S. Mahdavi, A.P. Blake, D.J. Richards, D.J. White
Screw (or helical) piles have been increasingly used to support a variety of structures such as pipelines, transmission towers, bridges and commercial buildings. Screw piles are steel tubes with one or more helical elements fabricated on the shaft that are screwed into the ground through the application of torque and thrust (vertical force) (Richards et al. 2019). This pile configuration increases the axial base resistance, allows a rapid, quiet and low-vibration installation, and enables reusability. These advantages have increased interest in their use as an alternative foundation solution for offshore wind turbines (OWTs) supported on jacket structures. However, given the much larger scale required to meet the axial load requirements of OWTs compared to current onshore applications, concerns have been raised regarding the large installation torque necessary for their installation (Sharif et al., 2020; Bittar et al., 2021).
Foundations
Published in Alan J. Lutenegger, Soils and Geotechnology in Construction, 2019
The technology has been around since the mid 1800s and was used extensively for about 60 years. It has not been until about the last 25 years that we have seen a very dramatic resurgence in its use throughout the world, probably because we now have high-capacity torque motors to perform the installation. The maximum load capacity of screw-piles and helical anchors is the lesser of the structural capacity of the steel section, the structural capacity of the connections between any shaft extensions, and the available strength of the soil. The load capacity available from the soil depends on soil strength and the geometry of the Helical Pile, including size, type, and length of the shaft, and the number, size, and spacing of the helical plates. Usually, the strength of the soil controls load capacity.
Centrifuge modelling of screw piles for offshore wind energy foundations
Published in Andrew McNamara, Sam Divall, Richard Goodey, Neil Taylor, Sarah Stallebrass, Jignasha Panchal, Physical Modelling in Geotechnics, 2018
C. Davidson, T. Al-Baghdadi, M.J. Brown, A. Brennan, J.A. Knappett, C. Augarde, W. Coombs, L. Wang, D.J. Richards, A. Blake, J. Ball
Screw piles have been proposed as a replacement for conventional straight-shafted piles for jacket supported wind turbine foundations (Byrne & Houlsby 2015, Spagnoli & Gavin 2015), as they offer several advantages. Firstly, installation is achieved through continuous simultaneous application of vertical crowd and rotational forces. This eliminates problems associated with pile driving hammers as the rotational installation method is significantly quieter (Byrne & Houlsby 2015, Knappett et al. 2014). Secondly, the superior axial capacity, compared to straight-shafted piles, generated by the helical plates and the soil trapped (soil-soil shear) between them is a significant advantage in resisting the substantial environmental loads acting on the jacket and turbine. Thirdly, screw piles can potentially reduce the amount of steel required for the foundations due to improved efficiency of the load carrying mechanisms, leading to cost savings for a wind farm project.
Calculation method and mechanism of ultimate side resistance of screw pile
Published in Marine Georesources & Geotechnology, 2023
Hong-wei Ma, Li Liu, Peng Wang, Song Yuan, Qing-rui He, Xiao-li Yang
Screw pile is a particular pile foundation which makes the screw thread interlock with soil by changing the pile side geometry. The continuous screw thread, with a large thickness and a small outer diameter, attached to the pile side disperses the vertical load into the soil around the pile, thus the pile's ultimate side resistance is improved and the settlement of the pile end is reduced (Xu, Zhang, and Xu 2010, Therar et al. 2017). On the other hand, the construction of screw pile will not cause serious environmental pollution and soil disturbance (Nesmith 2002). Therefore, screw pile is widely used in engineering with high requirements on foundation bearing capacity, settlement and environment, such as offshore wind power generation, offshore platform and sea bridge (Wang et al. 2017, and Cerfontain et al. 2020).
Numerical investigation on pullout capacity of helical piles under combined loading in spatially random clay
Published in Marine Georesources & Geotechnology, 2022
Po Cheng, Jia Guo, Kai Yao, Xuejian Chen
Helical piles, alternatively called screw piles or helical anchors, are one of the deep foundation types which are composed of a central steel shaft and single or multiple helical bearing plates fixed along the shaft (see Figure 1). The conventional uses of helical piles are primarily restricted to onshore industries, until recently, they have been gaining popularity as potential offshore application solutions due to many advantages, such as ease of installation, great efficiency and sustainable use of steel (Byrne and Houlsby 2015; Davidson et al. 2022; Spagnoli and Tsuha 2020).
A new modified method of predicting load-settlement behavior for large-diameter helical piles in sand considering nonlinear degradation of soil stiffness
Published in Marine Georesources & Geotechnology, 2023
Kang Shao, Qian Su, Kaiwen Liu, Xiangyu Han, Weimin Xiao, Dongxing Ren
Driven piles and screw piles have a different range and degree of influence on the soil during installation, although both are categorized as displacement piles that are either pushed or hammered into the ground. Screw piles are installed by screwing, mainly relying on torque, and secondly relying on crowd force. According to previous studies, the operative modulus degradation relationship was determined by back-calculation, which takes into account the effect of pile installation. The operative modulus degradation curves of piles with different installation effects vary.