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$1 BILLION SUBWAY BORES 9.7 MILES BENEATH BUSTLING CITY

Availability: Find a library where document is available. Order URL: http://worldcat.org/issn/08919526
Corporate Authors: McGraw-Hill, Incorporated 330 West 42nd Street New York, NY United States 10036
Publication Date: 1976-12-23

The method described permitted the bulk of excavation to be completed quickly so tunneling from the site could begin before the station walls were in place. A hydraulic shield was used to drive the tunnels 2300 ft to the next station. Hard granite in other tube sections, however, required blasting. The line generally lies at a depth of 82 to 115 ft and along a maximum 3% grade.