NEART NA GOITHE PILE DESIGN VERIFICATION

Seaway Heavy Lifting (SHL) instructed Innosea and Longitude, both LOC Group companies, to perform a verification for a 3 legged jacket foundation design at the Neart na Gaoithe (NNG) offshore wind farm site located approximately 15km east off the Fife coast in the outer Firth of Forth, Scotland.

The project comprised the Pre-Construction Design (Concept Design and Front-End Engineering Design) for the offshore foundations for the NNG project for which Longitude performed the geotechnical input in conjunction with KCI and Innosea’s structural design teams.

Longitude’s Scope of Work

Longitude provided the geotechnical design of piled foundation to support the jacket platform. The design included:
•Assessment of pile static tension and compression capacity
•Assessment of lateral spring supports to inform structural design

Approach

The following approach was undertaken to ensure the verification was in accordance with the main foundation design:

  • Assessment of axial pile capacity as per DNVGL-ST-0126, using partial factor of safety approach.
  • Axial pile capacity/behaviour:
    • Sand- and clay-type soils as per DNVGL-RP-C212 and API-RP-2GEO.
    • Sandstone-type soil as per Williams and Pells (1981) “Side Resistance rock sockets in sandstone, mudstone and shale”, and Zhang (2004) “Drilled Shafts in Rocks, Analysis and Design”.
  • Lateral pile capacity/behaviour:
    •  Sand- and clay-type soils as per DNVGL-RP-C212 and API-RP-2GEO.
    • Sandstone-type soil as per Reese (1997) “Analysis of Laterally Loaded Piles in Weak Rock”, and Liang et al (2009) “p-y Criterion for Rock Mass”.