While the shield chambers were being excavated, bottom headings were run along the lines of the river tunnels and continued until the lack of rock cover prevented their being driven further. These were afterward enlarged to the full section as far as possible. The typical working force in the shield chambers was as follows:
| Ten-hour Shifts. | |||
| Drilling and Blasting. | |||
| 1 | Foreman | @ | $3.50 |
| 6 | Drillers | " | 3.00 |
| 6 | Drillers' helpers | " | 2.00 |
| 1 | Blacksmith | " | 3.50 |
| 1 | Blacksmith's helper | " | 2.25 |
| 1 | Powderman | " | 2.00 |
| 1 | Waterboy | " | 2.00 |
| 1 | Nipper | " | 2.00 |
| 1 | Machinist | " | 3.00 |
| 1 | Machinist's helper | " | 1.80 |
| Mucking. | |||
| 1 or 2 | Foremen | @ | $3.00 |
| 16 | Muckers | " | 2.00 |
Erection of Shields.—The tunneling shields have been described in some detail in the section of this paper dealing with the contractor's plant. They consist essentially of two parts, the structural steelwork and the hydraulic fittings. The former was made by the Riter Conley Manufacturing Company, of Pittsburg, Pa., and put up by the Terry and Tench Company, of New York City; the hydraulic fittings were made and put in by the Watson-Stillman Company, of New York City.
On the New York side, the shields were built inside the iron lining of the shield chambers, hence no falsework was needed, as the necessary hoisting tackle could be slung from the iron lining; at Weehawken, however, the erection was done in the bare rock excavation, so that timber falsework had to be used. The assembly and riveting took about 2 weeks for each shield; the riveting was done with pneumatic riveters, using compressed air direct from the tunnel supply.
After the structural steel had been finished, the shields, which had hitherto been set on the floor of the chambers in order to give room for working over the top, were jacked up to grade; this involved lifting a weight of 113 tons. While the hydraulic fittings were being put in, the shields were moved forward on a cradle, built of concrete with steel rails embedded, on which the shield was driven for the length in which the tunnel was in solid rock.
The installation of the hydraulic fittings took from 4 to 6 weeks per shield. The total weight of each finished shield was about 193 tons. The completed shield, as it appeared in the tunnel, is shown by [Fig. 1, Plate XXXVIII]. The typical force working on shield erection was as follows:
| Ten-hour Shifts. | |||||
| Shield Erection. (Terry and Tench.) | |||||
| 1 | Superintendent | @ | $13.00 | per | day |
| 4 | Foremen | " | 5.50 | " | " |
| 1 | Timekeeper | " | 2.50 | " | " |
| 2 | Engineers | " | 4.50 | " | " |
| 34 | Iron workers | " | 4.50 | " | " |
| 7 | Laborers | " | 2.25 | " | " |
| Hydraulic Work. (Watson-Stillman Company.) | |||||
| 4 | Mechanics | @ | $4.00 | per | day |
| General Labor. (O'Rourke Engineering Construction Company.) | |||||
| 1 | Inspector | @ | $4.00 | per | day |
| 1 | Foreman | " | 4.00 | " | " |
| 8 | Laborers | " | 2.00 | " | " |
| 1 | Engineer | " | 2.50 | " | " |
PLATE XXXVIII.
TRANS. AM. SOC. CIV. ENGRS.
VOL. LXVII, NO. 1155.
HEWETT AND BROWN ON
PENNSYLVANIA R. R. TUNNELS: NORTH RIVER TUNNELS.