The Piling in Glauconitic Sands (PIGS) JIP: Reducing Geotechnical Uncertainty for U.S. Offshore Wind Development

Abstract

Abstract This paper presents insights from the Piling in Glauconitic Sand (PIGS) Joint Industry Project (JIP). Established in 2021, the JIP investigates geotechnical behavior of glauconite sands in relation to pile installation and long-term performance as relevant to offshore wind energy development along the U.S. Atlantic Outer Continental Shelf (OCS). The JIP comprises five energy developers and is led by the Norwegian Geotechnical Institute. The scope of work comprises (i) characterization of an onshore glauconite test site in New Jersey and glauconite/glauconitic sands from offshore lease areas, (ii) steel pipe piles driven using hydraulic and vibratory hammers, (iii) and axial tension, axial compression and lateral pile load testing. Novel site investigation methods include the effect of friction reducer geometry on cone penetration testing (CPT) resistance, cyclic CPT including water injection, and sampling of degraded glauconite sand from pile walls. The detailed instrumentation program included accelerometers and strain gauges during driving, grout-embedded sister bar strain gauges during axial compression and tension load testing, and fiber Bragg grating optical sensor measurement during axial compression and lateral load testing. In this paper, we present analysis of the CPT data and pile installation data including soil resistance to driving (SRD) and pile-soil setup during redrives/restrikes, and describe novel in situ sampling and testing of degraded glauconite sand. Degradation experienced by the glauconite sands during pile installation is consistent with observations from other regions including Belgium and is compared to artificial degradation performed in a laboratory setting. The JIP is the first comprehensive field and laboratory test program investigating glauconite sand behavior in the U.S. The data being collected is providing offshore wind developers an opportunity to reduce uncertainty and risk in pile installation and long-term performance, and gain insights into glauconite sand variability and geotechnical behavior across the U.S. Atlantic OCS to aid in future lease area development.