| Part. | No. | Material. | Weight, in pounds. |
|---|---|---|---|
| Middle top casting | 1 | Cast steel | 880 |
| End top castings | 2 | " " | 1,718 |
| Lining castings | 3 | " " | 18,232 |
| Sump segment | 1 | Cast iron | 3,560 |
| Total weight per sump, exclusive of bolts | 24,390 | ||
Turnbuckle Reinforcement for Cast-Iron Segments.—During the period of construction, a certain number of cast-iron segments, mostly in the roof, but in some cases at Manhattan in the invert, behind the river lines, became cracked owing to uneven pressures of the ground. Before the concrete lining was put in, considerable discussion occurred as to the wisest course to pursue with regard to these broken plates. It was finally thought best not to take the plates out, as more harm than good might be done, but to reinforce them with turnbuckles, as shown in [Fig. 15]. The number of broken segments was distributed as follows:
North Manhattan Tunnel 87, chiefly in silt (not under the river),
South Manhattan Tunnel 7, chiefly in silt (not under the river),
North Weehawken Tunnel 24, chiefly in sand (not under the river),
South Weehawken Tunnel 48, chiefly in silt, under the Fowler Warehouse.
The chief features of the tunnel lining have now been described, and, before giving any account of the methods of work, it will be well to mention briefly the salient features of the concrete lining which is placed within the actual lining.
Design of Concrete Lining.
This concrete lining will be considered and described in the following order:
The New York Shield Chambers,
Standard Cross-Section of Concrete Lining of Shield-Driven Tunnels,
Final Lines and Grades, and How Obtained,
Steel Rod Reinforcement of Concrete,
Cross-Passage Lining,
Special Provision for Surveys and Observations.
