Subway Tunnel Construction in New York City

Subway tunnel construction provides a variety of conditions requiring special equipment and methods. Tunnel sections vary as to shape, height and proximity to existing structures. Proven and new equipment and methods are used for excavation and concrete operations. A combination of roof bolt, timber and structural steel is used to support the excavated tunnel. Rubber-tired hauling equipment proved to be maneuverable and adaptable to a variety of tunnel operations. Crawler-mounted equipment for loading is selected because of its success doing similar work. Concrete equipment is selected and adapted to be maneuverable and flexible because of the variety placing requirements. Rock fall stops advance of tunnel excavation. Tunnel and void are filled with concrete to form support for falling rock. Rock excavation is carried out directly under operating railroad and passenger station. Support of overhead structure is done as excavation is advanced. Blasting in this area is limited to avoid damage to existing structure.