Manhattan Shield Chambers.—The Manhattan shield chamber construction will be first described. The Weehawken shield chambers have been described under the Land Tunnel Section, as they are of the regular masonry-lined Land Tunnels type, whereas the Manhattan chambers are of segmental iron lining with a concrete inner lining.
During the progress of excavation, the location of the New York shield chambers was moved back 133 ft., as previously described in the "Land Tunnel" Section, and when the location had been finally decided, there was a middle top heading driven all through the length now occupied by the shield chamber. Narrow cross-drifts were taken out at right angles to the top heading, and from the ends of these the wall-plate headings were taken out. Heavy timbering was used, as the rock cover was only about 6 ft., and the whole span to be covered was 60 ft. The process adopted was to excavate and timber the north side first, place the iron lining, and then excavate the south side, using the iron of the north side as the supports for the north ends of the segmental timbering of the south. The only incident of note was that at 2:00 A.M., on October 20th, 1904, the rock at the west end of the south wall-plate heading was pierced. Water soon flooded the workings, and considerable disturbance was caused in the New York Central Railroad yard above. The cavity on the surface was soon filled in, but to stop the flow of mud and water was quite a troublesome job.
TABLE 22.—Quantities of Work in Subaqueous Tunnels.
| Description, Quantity, Length, etc. | TYPE. | ||||||
|---|---|---|---|---|---|---|---|
| Manhattan shield chambers. | Cast iron, ordinary pocketless. | Cast iron, ordinary pocket. | Cast iron, heavy pocketless. | Cast steel, ordinary pocketless. | Total. | ||
| Length, in feet. | 59.00 | 4,374.99 | 2,146.3 | 5,522.05 | 152.66 | 12,255.00 ft. | |
| Excavation, in cubic yards. | Total. | 1,884 | 67,344 | 33,038 | 85,001 | 2,349 | 189,616 cu. yd. |
| Per linear foot. | 31.9 | 15.4 | 15.4 | 15.4 | 15.4 | ||
| Cast-iron tunnel lining, in pounds. | Total. | 847,042 | 39,643,120 | 19,715,405 | 61,559,845 | 121,765,412 lb. | |
| Per linear foot. | 14,357 | 9,061 | 9,186 | 11,148 | |||
| Cast-steel tunnel lining, in pounds. | Total. | 1,544,962 | 757,938 | 2,730,905 | 1,549,711 | 6,583,516 lb. | |
| Per linear foot. | 353.1 | 353.1 | 494.5 | 10,151.4 | |||
| Steel bolts and washers, in pounds. | Total. | 23,627 | 1,475,991 | 724,095 | 2,935,455 | 51,266 | 5,210,434 lb. |
| Per linear foot. | 400.46 | 337.37 | 397.00 | 581.59 | 335.82 | ||
| Rust joints, in linear feet. | Total. | 3,376 | 170,755 | 83,935 | 218,656 | 5,996 | 482,718 ft. |
| Per linear foot. | 57.2 | 39.0 | 39.1 | 39.6 | 39.3 | ||
| Concrete, in cubic yards. | Total. | 766 | 20,030 | 9,827 | 25,282 | 713 | 56,618 cu. yd. |
| Per linear foot. | 12.98 | 4.58 | 4.58 | 4.58 | 4.58 | ||
| Steel beams, plates, etc., in pounds. | Total. | 12,346 | 83,774 | 41,098 | 105,738 | 7,432 | 250,388 lb. |
| Per linear foot. | 2,092.5 | 19.1 | 19.1 | 19.1 | 48.7 | ||
| Steel bolts, hooks, etc., in pounds. | Total. | 1,328 | 36,980 | 18,142 | 46,675 | 1,471 | 104,596 lb. |
| Per linear foot. | 22.5 | 84.5 | 84.5 | 84.5 | 96.4 | ||
| Expanded metal, in pounds. | Total. | 594 | 2,215 | 1,086 | 2,795 | 62 | 6,752 lb. |
| Per linear foot. | 10.07 | 0.506 | 0.506 | 0.506 | 0.406 | ||
| Vitrified conduits, in duct feet. | Total. | 2,560 | 235,903 | 115,728 | 297,752 | 7,757 | 659,700 duct ft. |
| Per linear foot. | 43.49 | 53.92 | 53.92 | 53.92 | 50.81 | ||
TABLE 23.—Excavation and Iron Lining.
| North Manhattan. | North Weehawken. | South Manhattan. | South Weehawken. | ||
|---|---|---|---|---|---|
| Shaft and preliminary headings. | Begun. | June 10, '03. | June 11, '03. | June 10, '03. | June 11, '03. |
| Shaft and preliminary headings. | Finished. | December 11, '03. | September 1, '04. | December 11, '03. | September 1, 04 |
| Excavation of shield chamber. | Begun. | May 24, '04. | January 16, '05. | May 24, '04. | January 16, '05. |
| Excavation of shield chamber. | Finished. | January 21, '05. | March 25, '05. | May 13, '05. | April 19, '05. |
| Cast-iron lining of shield chambers. | Begun. | February 4, '05. | None. | May 15, '05. | None. |
| Cast-iron lining of shield chambers. | Finished. | March 13, '05. | None. | June 14, '05. | None. |
| Excavation of tunnels begun before installation of shield. | October 17, '04. | January 13, '05. | January 5, '05. | January 25, '05. | |
| Commenced building falsework for shield. | March 6, '05. | March 23, '05. | June 19, '05. | April 17, '05. | |
| Shield parts received at shaft. | March 11, '05. | March 20, '05. | June 22, '05. | April 24, '05. | |
| Erection of shield begun. | March 13, '05. | March 27, '05. | June 22, '05. | April 24, '05. | |
| Erection of shield (structural steel). | Finished. | March 27, '05. | April 12, '05. | June 8, '05. | May 6, '05. |
| Erection of shield (hydraulic fittings). | Finished. | May 11, '05. | May 25, '05. | August 27, '05. | June 13, '05. |
| First ring of permanent cast-iron lining put in. | May 12, '05. | May 29, '05. | August 27, '05. | June 14, '05. | |
| First air lock bulkhead wall. | Begun. | May 29, '05. | June 15, '05. | September 18, '05 | June 21, '05. |
| First air lock bulkhead wall. | Finished. | June 7, '05. | June 23, '05. | September 23, '05 | July 3, '05. |
| Air pressure first put in tunnel. | June 25, '05. | June 29, '05. | October 6, '05. | July 8, '05. | |
| Rock disappeared from invert of tunnel. | December 1, '05. | October 31, '05. | February 8, '06. | September 21, 05 | |
| First pair of bore segments built in tunnel. | December 9, '05. | January 12, '06. | February 16, '06. | December 12, '05 | |
| Rip-rap of river bulkhead wall met. | February 8, '06. | None. | April 11, '06. | None. | |
| First pile met (in river bulkhead wall at Manhattan, and Fowler warehouse foundation at Weehawken). | February 18, '06. | January 3, '06. | April 18, '06. | December 4, '06. | |
| Last pile met. | March 2, '06. | February 5, '06. | May 1, '06. | January 9 '06. | |
| First ring erected on river side of shore line. | March 3, '06. | February 6, '06. | May 9, '06. | January 19, '06. | |
| Removing hood of shield. | Begun. | March 27, '06. | February 6, '06. | May 9, '06. | January 19, '06. |
| Removing hood of shield. | Finished. | April 1, '06. | February 8, '06. | May 12, '06. | January 24, '06. |
| Second air-lock bulkhead wall. | Begun. | May 12, '06. | March 19, '06. | July 13, '06. | March 11, '06. |
| Second air-lock bulkhead wall. | Finished. | May 21, '06. | March 24, '06. | July 21, '06. | March 18, '06. |
| Tunnel holed through with meeting tunnel. | September 12, 1906. | October 9, 1906. | |||
| Last ring of permanent cast-iron lining built in. | October 9, 1906. | November 18, 1906. | |||
The excavation was begun on May 24th, 1904, and finished on May 15th, 1905. The segments were placed by an erector consisting of a timber boom supported by cross-timbers running on car wheels on longitudinal timbers at each side of the tunnel. Motion was transmitted to the boom by two sets of tackle, and the heavy (5,000-lb.) segments were easily handled. The erection of the lining was started on February 4th, 1905, and finished on June 14th, 1905.