With more than 500,000 visitors a day, New York’s Grand Central Terminal and Grand Central-42nd Street No. 7 Subway Line station is one of the busiest transit stops in the world. To improve passenger circulation between the subway station and terminal, a new passenger tunnel connecting the two was initiated by the Metropolitan Transportation Authority (MTA).
STV, as part of the design-build team led by Skanska, led the design for this complex underground connector. Because construction beneath East 42nd Street and Lexington Avenue required working near buildings, underground structure and utilities – with minimal flexibility for adjustments – STV’s team deployed an extensive rock excavation using the Sequential Excavation Methods (SEM). This highly adaptable tunneling technique systematically excavates and supports smaller sections of the tunnel to maintain ground stability, while maintaining uninterrupted service on the subway line.
In addition to this method, the team worked with specialized equipment such as Brokk-mounted drills and hydraulic machinery. The team also used advanced 3-D Finite Element Analysis, a computerized modeling method that predicts how structures will react to real-world forces. This approach resulted in a tunnel design that prioritized stability and public safety under shallow rock cover while minimizing ground settlement, groundwater seepage and construction impacts on existing utilities.
