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2014SumShotcreteEMag

Goin’ Underground Shotcreting on Frozen Ground By Paul H. Madsen T billion-dollar East Side Access (ESA) Pro- through the foundation piles of operating elevatedNBX extends under an active five-track-widesubway box, a major six-lane highway, as well as-he Northern Boulevard Crossing (NBX) isthe keystone portion of the massive multi gram by the Metropolitan Transit Authority subway line structure. All of the above presented Capital Construction (MTACC) to bring Long a unique challenge to the owner and contractor. Island Railroad trains into and out of New York NBX is the first and only soft-ground SEM tunnel City’s Grand Central Terminal. NBX constitutes project within the five Boroughs of New York and the link between the Queens Tunnels and Man- was constructed by a joint venture of Schiavone hattan Tunnels portions of ESA. The crossing Construction Co., LLC, and Kiewit Infrastructure consists of 120 ft (37 m) of 2000 ft2 (186 m2) Co. (S/K). cross-sectional area tunnel through soft ground, Construction on NBX started in February 2010 constructed using the sequential excavation with the SEM excavation starting in April 2012 method (SEM) under the protection of a struc- following access chamber excavation, grouting, tural frozen arch (Fig. 1). and ground freeze. Excavation was completed in Fig: 1: Drift layout 42 Shotcrete • Summer 2014


2014SumShotcreteEMag
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