Innovative Use of an Active Soil Nail Wall in Lieu of Pit Underpinning for a Historic Building-Paper

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The Stevens Gateway Project at Stevens Institute of Technology in Hoboken, New Jersey, involved constructing two four-story buildings with basements beside the historic Carnegie Laboratory of Engineering, built in 1902. Pit underpinning was initially specified to protect the Carnegie building during excavation, but the contractor proposed an active soil nail wall as a faster alternative.<br /><br />The site presented significant challenges: glacial soils with apparent cohesion, boulders, decomposed rock, and irregular existing foundations. These conditions would have made hand-excavated underpinning pits slow, difficult, and potentially hazardous, with risks of ground loss and settlement.<br /><br />Unlike conventional passive soil nail walls, the active system used prestressed nails designed to resist movement. Nails included free-stressing and bond lengths, with selected rows tested and locked off. The design incorporated the building surcharge and a stiff shotcrete facing to limit deflection. This addressed the project’s strict limit of 0.25 inches (6.35 mm) of vertical movement.<br /><br />Construction sequencing was adapted to reduce settlement risk. A soil berm was retained in front of the wall while nails were installed and cured; excavation and shotcrete placement then proceeded in short sections, limiting exposure of the finished slope. Rotary duplex drilling kept boreholes supported and reduced the risk of ground loss.<br /><br />The active soil nail wall successfully retained the soil beneath the Carnegie building while avoiding disturbance directly below its foundations. It shortened construction time and improved safety and productivity compared with pit underpinning. The authors conclude that active soil nailing can be an effective alternative where site constraints and difficult ground conditions make conventional underpinning impractical.

Keywords

Stevens Gateway Project

soil nail wall

active soil nailing

underpinning

Carnegie Laboratory

Hoboken New Jersey

building excavation

ground settlement

shotcrete facing

foundation protection