Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Frictional Effect of Helical Pile Installation in Uniform Clays
Meili Zhang1; Yuxia Hu1; Shah Neyamat Ullah2; Long Yu3
1Department of Civil, Environmental and Mining Engineering, Perth, Western Australia, Australia; 2School of Engineering & Technology, Central

Queensland University, Queensland, Australia; 3School of Hydraulic Engineering, Dalian University of Technology, Dalian, Liaoning, China

Bak et al, 2018). However, the onshore applications of helical piles arealmost always with small piles both in shaft and the helix diameters. For
example, in the field tests by Hoyt and Clemence (1989), Sakr (2012)and Lutenegger (2011), Prasad and Rao (1996), Schiavon et al (2016)
and centrifuge tests by Tshuha and Aoki (2010), the shaft diameter wasin the range of 0.0138m ~ 0.51m and the plate diameter of 0.15 m ~ 0.9
m. The 11-storey residential building foundation using helical piles wasstudied by Vito and Cook (2011), a 2-inch solid steel square shaft withplate diameter as 8, 10, 12 inches was used.
Although the research on onshore helical piles in sand, silt and clay canbe useful for offshore helical pile design, some of the findings may not
be suitable for large diameter helical piles. Moreover, the offshore
application is always in fully saturated soils.

ABSTRACTThe application of helical piles offshore has been attractive due to its‘quiet’ installation and retrieving potential, which makes it moreenvironmentally friendly and economical. In this paper, single large platehelical piles in uniform clays are studied for offshore applications. The
torsional installation of the helical piles is simulated using threedimensional large deformation finite element (LDFE) analysis with
Coupled Eulerian Largrangian (CEL) method in ABAQUS. The effects
of interface friction between the helical pile and the clay are studied on
the required torque and crowd force during torsional installations. It isfound that the friction coefficient has minimal influence on theinstallation crowd force but has a greater influence on the installation
torque required. The increased installation torque due to frictional effectcan be formulated as a linear function of the friction coefficient at a given
normalized penetration depth. The soil flow mechanism around thehelical plate is revealed to explain the frictional effects. To provide moreinsight, complementary small strain analysis is conducted studying helix
end effects modelled as a strip footing. The effects of plate embedment
depth (H) and the soil undrained shear strength (su) on helical pile
installation responses are also studied. In flat plate end bearing capacity
study, the horizontal plate end bearing factor (Nc) is similar to that ofvertical plate end bearing factor with embedment ratio of H/t  20. The
horizontal plate end bearing factor is independent of the plateembedment depth with embedment ratio of H/t  20.

Helical piles have potential to provide higher tensile and uplift capacity
than the traditional piles and use much smaller shaft diameter and thepile length compared to driven piles (Ullah, et al., 2019). Prasad, Rao(1996) conducted research on the lateral capacity of helical piles incohesive soils and found that the capacity was around 1.2-1.5 times
larger than the single straight pile shaft without plates with shaft diameterof 13.8mm.
Many researchers have studied the frictional effects on helical pile
installations and operations (Sharma et al., 2020; Akopyan, Akopyan,
2016; Fatnanta, Ongko, 2018). However, most of these researches
mainly focused the helical pile bearing capacity in the field tests. Yu etal. (2019) analyzed the influence of friction coefficient on the vertical,
horizontal forces and the bending moment of the spudcan installationnear a footprint. Zhao et al. (2015) carried out research on the influenceof interface friction coefficient using different shapes of helix (taperedand circular plate). However, no linkage was established between thefriction effect and the corresponding soil flow mechanisms.
In this paper, LDFE analysis is performed using the CEL method (Ullahand Hu, 2020). The numerical analysis is carried out after its validation
against centrifuge test data. The interface friction between the soil andthe pile is varied from fully smooth ( = 0) to full rough ( = 1.0). Basedon the numerical results, the installation torque and crowd force will be
formulated as functions of the pile friction coefficient.

KEY WORDS: Helical Pile; Uniform Clay; Large Deformation of FE;
Torsional Installation; Frictional Effect, Coupled Eulerian andLagrangian method (CEL)INTRODUCTION
Although the helical pile was originally proposed for the marine
environment development (Feld, 1953, Lutenegger, 2017), it has been
only used extensively onshore as deep foundations and to support
structures, such as transmission towers and lighthouses (Davidson et al,2018; Wang, 2013). Its application to secure offshore floating facilities,
such as floating wind turbines and wave generation devices, has become
attractive due to its ‘quiet’ installation and retrieving potential. The quiet
installation can eliminate the ‘noise’ generated due to impact installationof monopiles. The retrieval potential means that it can be re -used, whichmakes it more economical.
Many researchers have focused on the onshore applications in field/in
situ tests (Gavin et al, 2014, Lee et al, 2007) and laboratory tests such as
centrifuge tests and lab floor tests (Tsuha et al, 2013, Wada et al, 2017,

NUMERICAL ANALYSIS AND RESULTS
Model setup
The configuration of the single plate helical pile is shown in Fig. 1, whereL is the whole penetration length of the helical pile, H is the embedment
depth from the soil surface, d is the shaft diameter, p is the pitch of the1468