St Helier West Substation: TerraLink Retaining Wall and Soil-Nailed Embankments
The new JEC St Helier West Substation at Westpoint plays a vital role in safeguarding St Helier’s electrical supply for the future. This environmentally sensitive project required significant earthworks, including the design and construction of soil-nailed embankments and a Reinforced Earth TerraLink retaining wall. The wall incorporates galvanised steel reinforcing strips and precast concrete facing panels, ensuring durability and seamless integration into the surrounding landscape.
The retaining wall not only protects the substation but also features a public viewing platform overlooking St Aubin’s Bay, adding a community-focused element to the design.
Located in an old quarry, the project site posed unique challenges. The quarry embankments, shaped like a horseshoe, stand at approximately 60° and are reinforced with soil nails and mesh facing. The vertical-faced TerraLink retaining wall, designed and supplied by Geoquest, is founded at around 1.5 metres from the foot of these embankments.
Geoquest developed a friction link system to connect the retaining wall to the existing soil-nailed embankments. Bespoke connectors were manufactured to attach to the ends of the soil nails, with fish plates enabling the attachment of galvanised steel reinforcing strips. Overlapping these strips between the embankments and the retaining wall ensures a secure frictional connection across both structures.
Given the proximity of the embankments to the base of the retaining wall, the first 2.25 metres of the structure were backfilled with concrete, while the remainder was backfilled with 6I granular fill. To manage movement, a horizontal crack-inducing groove was cut into the facing panels at the interface between the concrete and granular fill. The retaining wall was topped with an in-situ concrete pedestrian parapet, clad in random granite block finish to complement the natural landscape.
This project highlights the innovative use of TerraLink retaining walls and soil nail systems to deliver a robust, sustainable solution that addresses environmental considerations while enhancing the surrounding community.
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