Field study of group effects on the pullout capacity of “deep” helical piles in sand

Bradshaw, Aaron S.; Cullen, Lindsay; Miller, Zachary

doi:10.1139/cgj-2021-0072

Field study of group effects on the pullout capacity of “deep” helical piles in sand

Journal Article · Fri Apr 01 04:00:00 EDT 2022 · Canadian Geotechnical Journal

DOI:https://doi.org/10.1139/cgj-2021-0072· OSTI ID:1980781

Bradshaw, Aaron S. ^[1]; Cullen, Lindsay ^[2]; Miller, Zachary ^[3]

Department of Civil and Environmental Engineering, University of Rhode Island, 2 East Alumni Avenue, Kingston, RI 02881, USA.; OSTI
Department of Civil and Environmental Engineering, University of Rhode Island, 2 East Alumni Avenue, Kingston, RI 02881, USA.
Triton Systems, Inc., 330 Billerica Road, Suite 200, Chelmsford, MA 01824, USA.

This paper presents the results of a field load test program used to investigate group effects on the pullout capacity of single-helix “deep” helical piles/anchors in sand. The high tensile capacity and silent installation of helical piles has given them serious consideration as an alternative to conventional deep foundations and anchors for offshore renewable energy structures. New offshore applications may consider the use of groups of helical piles to resist structural loads. Group interaction effects are known to occur in helical piles, but there is a scarcity of field data on groups in sands under tensile loading. This study involved the installation and load testing of single-helix 152mm diameter round shaft piles and pile groups embedded in sand to depths of 12 and 18 helix diameters below the ground surface. The study was designed to explore the effects of close pile spacing, group configuration (i.e., number of piles), and soil strength (i.e., friction angle) as interpreted from cone penetration test (CPT) resistance. The results showed group efficiencies ranging from about 0.6 to 1.0 at a horizontal spacing of 2 to 3 times the helix diameter in sands with friction angles of about 39° to 44°. The data from this study may also be useful for validation of numerical models for analysis of helical pile group interactions.

Research Organization:: Triton Systems, Inc., Chelmsford, MA (United States)

Sponsoring Organization:: USDOE Office of Science (SC)

DOE Contract Number:: SC0017969

OSTI ID:: 1980781

Journal Information:: Canadian Geotechnical Journal, Journal Name: Canadian Geotechnical Journal Journal Issue: 4 Vol. 59; ISSN 0008-3674

Publisher:: Canadian Science Publishing

Country of Publication:: United States

Language:: English

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