DRILLING AND BLASTING OPEN CUTS IN THE UPPER EAST OF MANHATTAN—PART OF THE 86TH STREET STATION FOR THE 2ND AVENUE SUBWAY LINE

摘要

As part of the ongoing 2nd Avenue Subway program, which will relieve major congestion for subway riders on Manhattan’s east side, MTA Capital Construction (MTA CC) contracted Skanska/Traylor Joint Venture (STJV) to excavate and concrete line the station cavern for the 86th St Station. Before excavation of the cavern could begin, STJV had to drill and blast a 36' wide × 190' long open cut on the south end of the station 70' below street level which would provide the access for the cavern portal. The excavation started east of 2nd Avenue next to a high rise apartment building and finished west of 2nd avenue underneath the basement of a building STJV demolished and adjacent to two historic/fragile brownstone buildings. To complicate matters, the excavation went below 2nd Avenue, under live vehicular and pedestrian traffic plus a myriad of utilities including gas, water, sewer, electrical and communication lines. This paper will describe the means and methods employed to balance expedited drill, excavation and rock support production with minimal impact to the community and surrounding buildings. The obstacles that were overcome include the stringent vibration criteria, continuous public observation, low headroom when working with utilities, very tight surface staging, controlling environmental impacts (noise, dust, air overpressure) and safety challenges when working in one of the most densely populated and influential areas of Manhattan, the Upper East Side.