Part 10

====================================+================+================| | North | North | | Manhattan. | Weehawken. | ------------------------------------+----------------+----------------| Shaft and preliminary headings. | June 10, '03. | June 11, '03. | Begun. | | | Shaft and preliminary headings. |December 11, '03|September 1, '04| Finished. | | | Excavation of shield chamber. Begun.| May 24, '04. |January 16, '05.| Excavation of shield chamber. |January 21, '05.| March 25, '05. | Finished. | | | Cast-iron lining of shield chambers.|February 4, '05.| None. | Begun. | | | Cast-iron lining of shield chambers.| March 13, '05. | None. | Finished. | | | Excavation of tunnels begun before |October 17, '04.|January 13, '05.| installation of shield. | | | Commenced building falsework for | March 6, '05. | March 23, '05. | shield. | | | Shield parts received at shaft. | March 11, '05. | March 20, '05. | Erection of shield begun. | March 13, '05. | March 27, '05. | Erection of shield (structural | March 27, '05. | April 12, '05. | steel). Finished. | | | Erection of shield (hydraulic | May 11, '05. | May 25, '05. | fittings). Finished. | | | First ring of permanent cast-iron | May 12, '05. | May 29, '05. | lining put in. | | | First air lock bulkhead wall. Begun.| May 29, '05. | June 15, '05. | First air lock bulkhead wall. | June 7, '05. | June 23, '05. | Finished. | | | Air pressure first put in tunnel. | June 25, '05. | June 29, '05. | Rock disappeared from invert of |December 1, '05.|October 31, '05.| tunnel. | | | First pair of bore segments built in|December 9, '05.|January 12, '06.| tunnel. | | | Rip-rap of river bulkhead wall met. |February 8, '06.| None. | First pile met (in river bulkhead |February 18, '06|January 3, '06. | wall at Manhattan, and Fowler | | | warehouse foundation at Weehawken). | | | Last pile met. | March 2, '06. |February 5, '06.| First ring erected on river side of | March 3, '06. |February 6, '06.| shore line. | | | Removing hood of shield. Begun. | March 27, '06. |February 6, '06.| Removing hood of shield. Finished. | April 1, '06. |February 8, '06.| Second air-lock bulkhead wall. | May 12, '06. | March 19, '06. | Begun. | | | Second air-lock bulkhead wall. | May 21, '06. | March 24, '06. | Finished. | | | ------------------------------------+----------------+----------------| Tunnel holed through with meeting | September 12, 1906. | tunnel. | | Last ring of permanent cast-iron | October 9, 1906. | lining built in. | | ====================================+================+================|

====================================+================+================| | South | South | | Manhattan. | Weehawken. | ------------------------------------+----------------+----------------| Shaft and preliminary headings. |June 10, '03. |June 11, '03. | Begun. | | | Shaft and preliminary headings. |December 11, |September 1, 04| Finished. |'03. | | Excavation of shield chamber. Begun.|May 24, '04. |January 16, '05.| Excavation of shield chamber. |May 13, '05. |April 19, '05. | Finished. | | | Cast-iron lining of shield chambers.|May 15, '05. |None. | Begun. | | | Cast-iron lining of shield chambers.|June 14, '05. |None. | Finished. | | | Excavation of tunnels begun before |January 5, '05. |January 25, '05.| installation of shield. | | | Commenced building falsework for |June 19, '05. |April 17, '05. | shield. | | | Shield parts received at shaft. |June 22, '05. |April 24, '05. | Erection of shield begun. |June 22, '05. |April 24, '05. | Erection of shield (structural |June 8, '05. |May 6, '05. | steel). Finished. | | | Erection of shield (hydraulic |August 27, '05. |June 13, '05. | fittings). Finished. | | | First ring of permanent cast-iron |August 27, '05. |June 14, '05. | lining put in. | | | First air lock bulkhead wall. Begun.|September 18, |June 21, '05. | |'05 | | First air lock bulkhead wall. |September 23, |July 3, '05. | Finished. |'05 | | Air pressure first put in tunnel. |October 6, '05. |July 8, '05. | Rock disappeared from invert of |February 8, '06.|September 21, 05| tunnel. | | | First pair of bore segments built in|February 16, |December 12, '05| tunnel. |'06. | | Rip-rap of river bulkhead wall met. |April 11, '06. |None. | First pile met (in river bulkhead |April 18, '06. |December 4, '06.| wall at Manhattan, and Fowler | | | warehouse foundation at Weehawken). | | | Last pile met. |May 1, '06. |January 9 '06. | First ring erected on river side of |May 9, '06. |January 19, '06.| shore line. | | | Removing hood of shield. Begun. |May 9, '06. |January 19, '06.| Removing hood of shield. Finished. |May 12, '06. |January 24, '06.| Second air-lock bulkhead wall. |July 13, '06. |March 11, '06. | Begun. | | | Second air-lock bulkhead wall. |July 21, '06. |March 18, '06. | Finished. | | | ------------------------------------+----------------+----------------| Tunnel holed through with meeting | October 9, 1906. | tunnel. | | Last ring of permanent cast-iron | November 18, 1906. | lining built in. | | ====================================+================+================+

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.

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 " "

After the shield was finished and in position, the first two rings of the lining were erected in the tail of the shield. These first rings were then firmly braced to the rock and the chamber lining; then the shield was shoved ahead by its own jacks, another ring was built, and so on.

The description of the actual methods of work in the shield-driven tunnels can now be given; this will be divided generally into the different kinds of conditions met at the working face, for example, Full Face of Rock, Mixed Face, Full Face of Sand and Gravel, Under River Bulkhead, and Full Face of Silt.

The last heading is the one under which by far the longest length of tunnel was driven, and, as not much has hitherto appeared descriptive of the handling of a shield, through this material, considerable space will be devoted to it.

_Full Face of Rock._--As was described when dealing with the shield chambers, as much as possible of the rock excavation was done before the shields were installed. On the New York side, about 146 ft. of tunnel was completely excavated, with 71 ft. of bottom headings beyond that, and at Weehawken, 58 and 40 ft. of tunnel and heading beyond, respectively. This was chiefly done to avoid handling the rock through the narrow shield doors. Test holes were driven ahead at short intervals to make sure that the rock cover was not being lost, but, nevertheless, at Weehawken, on February 14th, 1905, a blast broke through the rock and let the mud flow in, filling the tunnel for half its height for a distance of 300 ft. from its face.

Throughout the rock section the shield traveled on a cradle of concrete in which were embedded either two or three steel rails. In the portion in which the whole of the excavation had been taken out, it was only necessary to trim off projecting corners of rock. In the portion in which only a bottom heading had been driven, the excavation was completed just in front of the shield, the drilling below axis level being done from the heading itself, and above that from the front sliding platforms of the shield. The holes were placed near together and drilled short, and very light charges of powder were used, so as to lessen the chance of knocking the shield about too much. In this work the small shield doors hampered the work greatly, and it might have been well to have provided a larger bottom opening which could have been subdivided or partly closed when soft ground was met; on the other hand, the quantity thus handled was small, owing to the fact that the greater part of the rock was excavated before the shields were installed.

The space outside the lining was grouted with a 1:1 mixture of Portland cement and sand. Large voids were hand-packed with stone before grouting. The details of grouting will be described later.

A typical working gang is given herewith. Two such gangs were worked per shield per 24 hours, 10 hours per shift. All this work was done under normal air pressure.

_General:_

½ Tunnel superintendent @ $200.00 per month 1 Assistant tunnel superintendent " 5.00 per day 1 General foreman " 5.00 " " ½ Electrician " 3.50 " " ½ Electrician's helper " 3.00 " " ½ Pipefitter " 3.00 " " ½ Pipefitter's helper " 2.75 " "

_Drilling:_

1 Foreman " 5.00 " " 3 Drillers " 4.00 " " 3 Drillers' helpers " 3.00 " " 1 Nipper " 2.50 " " ½ Waterboy " 2.50 " " ½ Powderboy " 2.75 " "

_Mucking:_

1 Foreman " 3.50 " " 8 Muckers " 2.75 " "

_Erecting Iron and Driving Shield:_

1 Erector runner " 4.00 " " 3 Iron workers " 3.00 " "

The duties of such a gang were as follows: The tunnel superintendent looked after both shifts of one shield. The assistant or "walking boss" had charge of all work in the tunnel on one shift. The general foreman had charge of the labor at the face. The electricians looked after repairs, extensions of the cables, and lamp renewals. The pipefitters worked in both tunnels repairing leaks in pipes between the power-house and the working faces, extending the pipe lines, and attending to shield repairs, and in the latter work the erector runner helped.

The drillers stuck to their own jobs, which were not subject to interruption as long as the bottom headings lasted. One waterboy and one powderboy served two tunnels. The muckers helped the iron men put up the rings of lining, as well as doing their own work. The iron men tightened bolts, whenever not actually building up iron. The list does not include the transportation gang, which will be described under its own heading.

The rate of progress attained was 4.2 ft. per day per shield where most of the excavation had been done before, and 2.1 ft. where none had been done before.

When the shields had got far enough away from the shield chamber, and before rock cover was lost, the first air-lock bulkhead walls were put in.

_Air-Lock Bulkhead Walls._--The specifications required these walls and all their fittings to be strong enough to stand a pressure of 50 lb. per sq. in. Accordingly, all the walls were of concrete, 10 ft. in thickness, except the first two, which were 8 ft. in thickness, and grouted up tight.

There were three locks in each bulkhead wall capable of holding men, namely, the top or emergency lock which is set high in order to afford a safe means of getting away in case of a flood; this lock was used continuously for producing the lines and levels into the tunnels. It was very small and cramped for this purpose, and a larger one would have been better, both for lines and emergencies. This lock was directly connected with the overhead platform (also called for in the specifications) which ran the whole length of the tunnels. Side by side, on the level of the lower or working platform of the tunnel, were the man lock and the muck lock. In addition a number of pipes were built in to give access to the cables and for passing pipes, rails, etc., in and out.

After each tunnel was about 1,200 ft. ahead of the first walls, a second wall was built just like the first, and no others were put in, so that altogether there were eight walls. This second wall not only gave an added safeguard to the tunnel but enabled the air pressure at the working face to be divided between the two walls, and this compression or decompression in stages, separated by a spell of walking exercise, was found to be very good for the health of those working in the air.

_Mixed Face._--When the rock cover became so thin that it was risky to go on without the air pressure, the air pressure was turned on, starting with from 12 to 18 lb., which was enough to stop the water from the gravel on top of the rock. At first, when the surface of the rock was penetrated, the soft face was held up by horizontal boards braced from the shield until the shield was shoved. The braces were then taken out and, as soon as the shield had been shoved, were replaced by others. As the amount of soft ground in the face increased, the system of timbering was gradually changed to one of 2-in. poling boards resting on top of the shield and supported at the face by vertical breast boards, in turn held by 6 by 6-in. walings braced both through the upper doors to the iron lining and from the sliding platforms of the shield. The latter were in their forward position before the shield was shoved, the pressure being turned off and the exhaust valves opened just before the shove began. As the shield went ahead, the platform jacks gradually exhausted and thus held enough pressure on the face to keep it up. Fig. 17 is a sketch of this method. In driving through mixed ground a typical working gang was about as follows:

_General:_

1/3 Tunnel superintendent @ $300.00 per month 1 Assistant tunnel superintendent " 5.00 per day 1 General foreman " 5.00 " " ½ Electrician " 3.50 " " ½ Electrician's helper " 3.00 " " ½ Pipefitter " 3.25 " " ½ Pipefitter's helper " 3.00 " "

_Drilling:_

1 Foreman " 5.00 " " 2 Drillers " 3.25 " " 2 Drillers' helpers " 3.00 " "

_Timbering:_

2 Timbermen @ $2.50 per day 2 Timbermen's helpers " 2.00 " "

_Mucking:_

1 Foreman " 3.50 " " 6 Muckers " 2.75 " "

_Erecting Iron and Driving Shield:_

1 Erector runner " 3.25 " " 3 Iron workers " 3.00 " "

The average rate of progress was 2.6 ft. per day.

In this case there were three such gangs, each on an 8-hour shift.

_Full Face of Sand and Gravel._--This condition of affairs was only met at Weehawken. Two systems of timbering were used. In the first system, Fig. 17, the ground was excavated 2 ft. 6 in. ahead of the cutting edge, the roof being held by longitudinal poling boards, resting on the outside of the skin at their back end and on vertical breast boards at the forward end. When the upper part of the face was dry, it was held by vertical breast boards braced from the sliding platform and through the shield doors to cross-timbers in the tunnel; the lower part, which was always wet, was held by horizontal breast boards braced through the lower shield pockets to cross-timbers in the tunnel. This system worked all right as long as the ground in the top was sandy enough and had sufficient cohesion to allow the polings to be put in, but, when the upper part was in gravel, thus making it impossible to put in the longitudinal polings or the vertical breasting, the second system came in. Here the excavation was only carried 1 ft. 3 in. (half a shove) ahead of the cutting edge, and the longitudinal polings were replaced by transverse boards supported by pipes which were placed in the holes provided in the shield to accommodate some telescopic poling struts which had been designed but not made. These pipes acted as cantilevers, and were in two parts, a 2½-in. pipe wedged tight into the holes and smaller pipes sliding inside them. After a small section of the ground had been excavated, a board was placed against it, one of the pipes was drawn out under it, and wedges were driven between it and the board. These polings were kept below the level of the hood, so that when the shield was shoved they would come inside of it; in addition, they were braced with vertical posts from the sliding platforms. The upper part of the face was held by longitudinal breast boards braced from the sliding platform by vertical "soldier" pieces. The lower part of the face was supported by vertical sheet-piling braced to the tunnel through the lower doors. Sometimes two rows of piling were used, but generally one, as shown in Fig. 17. Notwithstanding the fact that the breasting was only 1 ft. 3 in. ahead of the hood, the shield was moved its full stroke of 2 ft. 6 in., the ground around the cutting edge of the hood being scraped away by men working bars in the place from which the temporary breast boards at the circumference had been removed. The back pressure on the sliding platform jacks, when the exhaust valves were only partly open, offered a good deal of resistance, and held the face as long as the movement of the shield was continuous.