Transactions of the American Society of Civil Engineers, Vol. LXVIII, Sept. 1910 / The New York Tunnel Extension of the Pennsylvania Railroad. / The North River Tunnels. Paper No. 1155

by Bertram Henry Majendie Hewett; W. L. Brown

Methods of Construction.

The following is an account of the methods used by the contractor in carrying out the plans which have already been described. First, it may be well to point out the sequence of events as they developed in this work. These events may be divided into six periods.

1.—Excavation and Iron Lining: June, 1903, to November, 1906;

2.—Caulking and grummeting the iron lining: November, 1906, to June, 1907;

3.—Surveys, tests and observations: April, 1907, to April, 1908;

4.—Building cross-passages and capping pile bores: April, 1908, to November, 1908;

5.—Placing the concrete lining: November, 1908, to June, 1909;

6.—Cleaning up and various small works: June, 1909, to November, 1909.

The tunnels were under an average air pressure of 25 lb. per sq. in. above normal for all except Periods 5 and 6, during which times there was no air pressure in the tunnels.

All the work will be described in this paper except that under Period 3 which will be found in another paper.

Period 1.—Excavation and Iron Lining, June, 1903, to November, 1906.—[Table 23] gives the chief dates in connection with this period.

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.

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.

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:
	⅓	Tunnel superintendent	@	$300.00	per	month.
	1	Assistant tunnel superintendent	"	5.00	per	day.
	1	General foreman	"	5.00	"	"
	½	Pipefitter	"	3.25	"	"
	½	Pipefitter's helper	"	2.75	"	"
	½	Electrician	"	3.00	"	"
	½	Electrician's helper	"	2.75	"	"
Timbering:
	3	Timbermen	"	2.50	"	"
	3	Timbermen's helpers	"	2.00	"	"
Mucking:
	1	Foreman	"	3.50	"	"
	6	Muckers	"	2.75	"	"
Erecting Iron and Driving Shield:
	1	Erector runner	"	3.25	"	"
	1	Foreman	"	4.00	"	"
	4	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.

On one occasion, when for some reason the shield was stopped with the shove only partly done, and the exhaust valves had not been shut off, the platforms continued to slide and allowed the face to collapse; the shield platforms and doorways, however, caught the falling sand and gravel and the flow choked itself.

As soon as the rock surface was penetrated and the sand and gravel were met, which happened almost at the same time in the two Weehawken Tunnels, the escape of air increased enormously, and it at once became clear that it was impossible to keep enough air in the two tunnels by the methods then in use, even when working the three compressors, each capable of compressing 4,400 cu. ft. of free air per min. at top speed. When the shields just entered the sand and gravel, the face had been held by light breasting, without any special effort to prevent the escape of air, but when it was found impossible to supply enough air, a large amount of straw and clay was used in front of the boards.

This cut down the escape, but, as much air was escaping through the joints of the iron lining, these were plastered with Portland cement. Even then, the loss was too great, therefore one tunnel was shut down entirely and all the air was sent to the other. This allowed a pressure of 10 lb. to be kept up in the working tunnel, and this, though less than the head, was enough to allow progress to be made. In order to use one tunnel as a drain for the other, the two faces were always kept within 150 ft. of each other by working them alternately. The timbered face was never grouted, though this would have reduced the loss of air, as at the same time it would have decreased the progress very much, and any one who saw the racing engines in the power-house, and realized that a breakdown of one of them would mean the loss of the faces, was ready to admit that the quicker this particular period was cut short, the better.

Above the sand and gravel lay the silt, and, when it showed in the roof, the escape of air was immediately reduced and the two faces could be worked simultaneously. Almost at the same time the piles supporting the large warehouse, known as the Fowler Building, were met. Although the face now took much less timber, the same system of breast boards as had been used in the gravel was kept up, but in skeleton form. They were set 2 ft. 6 in. ahead of the shield, however, instead of 1 ft. 3 in., and the transverse roof poling boards were replaced by longitudinals resting on the shield. The more piles in the face the less timbering was done. The piles were cut into handy lengths with axes and chisels.

All timbering was light compared with the weight of the ground, but, as the shove took place as soon as the set was made, it served its purpose. When a face was closed down the whole system was greatly reinforced by braces from the shield, the face of which was closed by the doors.

In driving through such a face the typical 8-hour shift gang was about as follows:

General:
	⅓	Tunnel superintendent	@	$300.00	per	month.
	1	Assistant tunnel superintendent	"	5.00	per	day.
	1	General foreman	"	5.00	"	"
	½	Pipefitter	"	3.25	"	"
	½	Pipefitter's helper	"	2.75	"	"
	½	Electrician	"	3.00	"	"
	½	Electrician's helper	"	2.75	"	"
Timbering:
	3	Timbermen	"	2.50	"	"
	3	Timbermen's helpers	"	2.00	"	"
Mucking:
	1	Foreman	"	3.50	"	"
	6	Muckers	"	2.75	"	"
Erecting Iron and Driving Shield:
	1	Erector runner	"	3.25	"	"
	1	Foreman	"	4.00	"	"
	4	Iron workers	"	3.00	"	"

The drillers were not kept on after the rock disappeared; a foreman was added who divided his time between iron erection and mucking.

The average rate of progress in sand and gravel without piles was 5.1 ft. per day per shield. When piles and silt were met in the upper part of the face, the speed increased to 7.0 ft. per day.

Passing Under River Bulkhead.—At Weehawken no trouble was found in passing under the river wall, as the bulkhead consisted of only cribwork supported on silt, and, though the piles obstructed the motion of the shield, they were easily cut out, and the cribwork itself was well above the top of the shield.

On the New York side, however, conditions were not nearly as good. The heavy masonry bulkhead was supported on piles and rip-rap, as shown in [Fig. 18]. The line of the top of the shield was about 6 ft. above the bottom of the rip-rap, the spaces between the stones of which were quite open and allowed a free flow of water directly from the river. As soon, therefore, as the cutting edge of the shield entered the rip-rap there was a blow, the air escaping freely to the ground surface behind the bulkhead and to the river in front of it. Clay puddle, or mud made from the excavated silt, was used in large quantities to plug up the interstices between the stone in the working face, the air pressure being slightly greater than that needed to keep out the water holding it in place. The excavation of the rip-rap was a tedious affair, for it had to be removed one stone at a time and the spaces between the newly exposed stones plugged with mud immediately. One man stood ready with the mud while another loosened the stones with a bar. When the shield had advanced its own length in the rip-rap, another point for the escape of the air was exposed at the rear end of the shield. This loss was closed at the leading end of the last ring with mud and cement sacks.

As long as the shield was stationary it was possible, by using these methods and exercising great care and watchfulness, to prevent excessive loss of air; but, while the shield was being shoved ahead, the difficulties were much increased, for the movement of the shield displaced the bags and mud as fast as they were placed, and it was only by shoving slowly and having a large number of men looking out for leaks and stopping them up the instant they developed that excessive loss of air could be prevented. In erecting the iron lining, as each segment was brought into position, it was necessary to clean off the leading surface of the previous ring and the adjacent portion of the tail of the shield; this was always accompanied by a slight "blow," and for some time the air pressure in the tunnel dropped from 25 to 20 lb., that is, from greater than the balancing pressure to less, every time a segment was placed, and on two occasions the "blow" became so great that the tunnel pressure was reduced considerably further, and in consequence the water from the river rushed in and was not stopped until it had risen about 4 ft. in the tunnel invert. On such occasions the surface of the river was greatly disturbed, rising more than 20 ft. in the air in a sort of geyser. A large quantity of grout (about 2,500 bbl. of cement and a similar quantity of sand in the North Tunnel and 1,000 bbl. in the South Tunnel) was used at this point; it was forced through the tunnel lining immediately behind the shield, greatly reducing the loss of air and helping to bind the rip-rap together.

When the shield had traveled 25 ft. through the rip-rap, the piles which support the bulkhead were met. One hundred of these which were spaced at 3-ft. centers in each direction, were cut out of the path of each shield in a distance of 35 ft. The presence of the piles caused considerable extra labor, as each pile had to be cut into several pieces with axes to enable it to be removed through the shield doors, otherwise they presented no difficulties. It was not necessary to timber the face, as the piles supported it most effectively.

When the river line had been passed, the "blow" still continued, and as there was no heavy ground above the tunnel the light silt was carried away into the water by the escaping air. At one time the cover over the crown of the tunnel was reduced to such an extent that for a distance of 30 ft. there was less than 10 ft. of very soft silt, and in some places none at all. Therefore, the shield was stopped and the air pressure reduced until it was less than the balancing pressure; the blow then ceased, and about 28,000 cement bags filled with mud were dumped into the hole (the location made it impossible to dump them en massefrom a scow). They were then weighted down with rip-rap. This sealed the blow, and the work was continued without any further disturbance from this source. Just before the blow reached its maximum it was found that two of the piles which had been encountered were directly in the path of one of the proposed screw-piles. It was therefore decided to pull these, and this was done with two 40-ton hydraulic jacks supported by the upper sliding platforms and acting on a horizontal timber which was connected to the piles by tie-rods and chains. The working force here was similar to that employed in the sand and gravel section previously described.

In Full Face of Silt.—A full face of silt was first met under the New York Central Railroad freight yard on the New York side. Up to this point the ground passed through had been either solid rock or a mixed face of rock and gravel. In both of these the full excavation had to be taken out before the shield could be shoved, and the soft ground had needed timbering. When the rock, gravel, and hardpan gave place to a full face of silt, the timber was removed, all the shield doors were opened, and the shield was shoved into the ground without any excavation being done by hand ahead of the diaphragm. As the shield advanced, the silt was forced through the open doors into the tunnel. After the work had gone on in this way for some time, taking in about 90% of the full volume of the tunnel excavation per foot forward, the air pressure was raised from 20 to 22 lb. The result was that the silt in the face got harder and flowed less readily through the shield, and the amount taken in fell to about 65% of the full volume. This manner of shoving at once caused a disturbance on the surface and the railroad tracks above the tunnel were raised, so that the pressure was lowered to 16 lb., then the muck got softer and the full volume of excavation was taken in; after a while the pressure was again raised to 20 lb.

The forcing of the shield through the silt resulted in a rising of the bed of the river, the amount that the bed was raised depending on the quantity of material brought into the shield.

If the whole volume of excavation was being brought in, the surface of the bed was not affected; when about 50% was being taken in, the surface was raised about 3 ft.; if the shield was being driven blind, the bed was raised about 7 ft.

The number of open doors was regulated so as to take in the minimum quantity of muck consistent with causing no surface disturbance. On the average, in the North Manhattan Tunnel, all the doors were open, but in the South Tunnel there were generally only five or six out of the total nine.

In front of the bulkhead wall at Manhattan the tunnels were under Pier No. 72. This structure was supported on wooden piles, some 80 ft. or more in length, which came down below the tunnel invert. The piles which lay directly in the path of the tunnels, with a few exceptions, had been pulled. In driving the tunnels through this section, great care had to be taken not to disturb the piles on either side of the tunnels, as they supported a heavy trestle used in disposing of the excavation from the open cut in the terminal yard. To avoid such disturbance, a large portion of the total excavation had to be taken through the shields.

The first shield which passed the river bulkhead was the south one at Weehawken. As soon as this line was crossed the silt was found to be much softer than behind the wall, in fact it was like a fluid in many of its properties. The fluidity could be changed by varying the tunnel air pressure; for example, when the air pressure was made equal to the weight of the overlying material (water and silt), the silt was quite stiff, and resembled a rather soft clay; but when the air pressure was from 10 to 15 lb. per sq. in. lower, it became so liquid that it would flow through a 1½-in. grout hole in the lining, in a thick stream, at the rate of from 10 to 50 gal. per min. as soon as the plug was taken out. This was the point to which the contractor had long looked forward, as he expected to be able to close all his shield doors and drive the rest of the way across without taking in a shovelful of muck, as had just been done under the Hudson River, on the South Tunnel of the Hudson and Manhattan Railroad Company's Tunnels between Morton Street, New York City, and Hoboken, N. J. The doors were shut and the shield was shoved; the tunnel at once began to rise rapidly, notwithstanding that the heaviest possible downward leads that the clearance between the iron and the shield would allow were put on. At the same time, the pressures induced in the silt by the shield shouldering the ground aside caused the iron lining to rise about 2 in. as soon as the shield left it, and also distorted it, the horizontal diameter decreasing and the vertical diameter increasing by about as much as 1¼ in. An anxious discussion followed these phenomena, as the effects had been so utterly unexpected, and a good many different theories were advanced as to the probable cause. It was thought that the hood of the shield might have something to do with the trouble. The shield was stopped, the hood removed, the doors were shut, and the driving continued. The same trouble was found, and it was impossible to keep to grade. Work was stopped, and the question was thoroughly debated; finally, on January 31st, 1906, the chief engineer directed that one of the shield doors be opened as an experiment and 50% of the excavation taken in.

The effect was instantaneous, the shield began to come down to grade at once, and it soon became necessary to close the door partially and reduce the quantity of muck taken in in order to prevent the tunnel from getting below grade. The other troubles from distortion, etc., ceased at the same time.

It was soon found that a powerful aid in the guidance of the shield was thus brought to hand, for, if high, the shield could be brought down by increasing the quantity of muck taken in, if low, by decreasing it. From this time forward, the quantity of muck taken in at each shove was carefully regulated according to the position of the tunnel with regard to grade and the nature of the ground. The quantity varied from nothing to the full volume displaced by the tunnel, and averaged 33% of the latter.

To regulate the flow, the bottom middle door was fitted with two steel angles behind which were placed 6 by 6-in. timbers. In this way the opening could be entirely closed or one of any size left. The muck flowed into the tunnel in a thick stream, as shown in [ Fig. 2, Plate XXXV], and, by regulating the rate of shove it could be made to flow just as fast as it could be loaded into cars.

In driving through the silt, the typical gang per shift of 8 hours per shield was as follows:

General:
	⅓	Tunnel superintendent	@	$300	per	month
	1	Assistant tunnel superintendent	"	6.00	per	day
	1	General foreman	"	5.00	"	"
	½	Electrician	"	3.50	"	"
	½	Electrician's helper	"	3.00	"	"
	1	Foreman	"	4.00	"	"
	2	Pipefitters	"	3.50	"	"
	2	Pipefitters' helpers	"	3.25	"	"
Mucking:
	1	Foreman	"	4.00	"	"
	6	Muckers	"	3.00	"	"
Erecting Iron and Driving Shield:
	1	Foreman	@	$4.00	per	day
	1	Erector runner	"	3.50	"	"
	4	Iron workers	"	3.00	"	"
	3	Laborers	"	3.00	"	"

Three such shifts were worked per day, and the air pressure averaged 25 lb. per sq. in.

The increase in the number of pipefitters was due to the greatly increased speed, and also the steadily increasing length of completed tunnel. The three laborers in the erection gang spent their whole time tightening bolts. The rate of progress in the silt under the river per ring of 2½ ft. was 3 hours 21 min., exclusive of all time when work was actually suspended. For a considerable part of the time only two 8-hour shifts were worked, owing to a shortage of iron caused by the change in the design of the lining, whereby the original lining was changed to a heavier one, and, as the work was also stopped for experiments and observations, the average of the actual total time, including all the time during which work was suspended, was 5 hours 32 min. per ring, or 10.8 ft. per day.

The junction of the shields under the river was made as follows: When the two shields of one tunnel, which had been driven from opposite sides of the river approached within 10 ft. of each other, the shields were stopped, a 10-in. pipe was driven between them, and a final check of lines and levels was made through the pipe. Incidentally, also, the first through traffic was established by passing a box of cigars through the pipe from the Manhattan shield to that from Weehawken. One shield was then started up with all doors closed while the doors on the stationary shield were opened so that the muck driven ahead by the moving shield was taken in through the other one's doors. This was continued until the cutting edges came together. All doors in both shields were then opened and the shield mucked out. The cutting edges were taken off, and the shields moved together again, edge of skin to edge of skin. The removal of the cutting edge necessitated the raising of the pressure to 37 lb. As the sections of the cutting edges were taken off, the space between the skin edges was poled with 3-in. stuff. [Fig. 1, Plate XXXIX], is a view of the shields of the North Tunnel after being brought together and after parts of the interior frames had been removed. When everything except the skins had been removed, iron lining was built up inside the skins, the gap at the junction was filled with concrete, and long bolts were used from ring to ring on the circumferential joint. Finally, the rings inside the shield skins were grouted.

In order to make clear the nature of the work done in building these shield-driven tunnels in silt, a short description will be attempted, this description falling into three main divisions, namely, Shoving the Shield, Pushing Back the Jacks, and Erecting the Iron Lining.

Shoving the Shield.—This part of the work is naturally very important, as the position of the shield determines within pretty narrow limits the position of the iron built within it, hence the shield during its forward movement has to be guided very carefully. On this work certain instructions were issued for the guidance of the foreman in charge of the shield. These instructions were based on results of "checks" of the shield and iron's position by the engineering corps of the Company, and comprised, in the main, two requirements, namely, the leads that were to be got, and the quantity of muck to be taken in. The "lead" is the amount that the shield must be advanced further from the iron, on one side or the other, or on the top or bottom, as measured from the front face of the last ring of iron lining to the diaphragm of the shield. These leads are not necessarily true leads from a line at right angles to the center line, as the iron may have, and in fact usually does have, a lead of its own which is known and allowed for when issuing the requirements for the shove.

The foreman, knowing what was wanted, arranged the combination of shield jacks which would give the required leads and the amount of opening on the shield door which would give the required amount of muck. To see how the shield was going ahead, a man was stationed at each side at axis level and another in the crown. Each man had a graduated rod on which the marks were so distinct that they could be read by anyone standing on the lower platform. These rods were held against the shield diaphragm, and, as it advanced, its distance from the leading end of the last ring could be seen by the man in control of the jack valves. If he found that he was not getting the required leads, he could change the combination of jacks in action. As the time of a shove was often less than 10 min., the man had to be very quick in reading the rods and changing the jacks. If it was found that extensive change in the jack arrangement was wanted, the shove could be stopped by a man stationed at the main hydraulic control valve; but, as any such stoppage affected the quantity of muck taken in, it was not resorted to unless absolutely necessary.

PLATE XXXIX.
TRANS. AM. SOC. CIV. ENGRS.
VOL. LXVIII, No. 1155.
HEWETT AND BROWN ON
PENNSYLVANIA R. R. TUNNELS: NORTH RIVER TUNNELS.

If the quantity of muck coming in was not as desired, a stop had to be made to alter the size of the opening, and if, while this was being done, the exhaust valves were not closed quite tight, the silt pressure on the face of the shield would force it back against the iron. This fact was sometimes taken advantage of when a full opening did not let in the desired quantity, for the shield could be shoved, allowed to return, and shoved again.

The time taken to shove in silt varied greatly with the quantity of material taken in; for shoving and mucking combined, it averaged 66 min., with an average of 13 cu. yd. of muck disposed of, or about 5 min. per cu. yd. of material.

Pushing Back the Jacks.—This was a simple matter, and merely consisted in making the loose push-back connection to each jack as it had to be sent back. Some of the jacks became strained and bent, and had to be taken out and replaced. Where there was silt pressure against the face of the shield, the hydraulic pressure had to be kept on until the ring was erected. In such cases, only two or three jacks could be pushed back at a time, and only after a segment had been set in position, and the pressure taken on it, could the next jack be pushed back, and so on around the ring. The time between the finish of the shove (hydraulic pressure turned off) and the placing of the first segment, was occupied in pushing back the bottom jacks and cleaning dirt off the tail of the shield, and averaged about 14 min.

Erecting the Iron Lining.—As soon as the shove was over, the whole force, when in silt, set to work at building up the iron and then tightening the bolts so that the shield could be shoved again. A section of the tunnel with bolting and working platform is shown on [Plate XL].

In the early part of the work, when the ground was being excavated ahead of the shield, the whole force, with the exception of those working in front of the shield, was engaged in erecting the iron, but, as soon as this was done, most of the men returned to the mucking, and only the iron workers continued to tighten up bolts. On the other sections, where the shield was shoved into the silt without excavating ahead, as soon as the shove was completed, the whole force was engaged in the erection of the iron and the tightening of the bolts, until they were so tight that the shield could be shoved again for another ring.

The iron was brought into the tunnel on flat cars, two segments to the car, and was lifted from the car and lowered into the invert of the shield by a block and fall and chain sling, as shown in [ Fig. 2, Plate XXXIX]. The bottom three or four segments were pushed around into position with the erector, the head simply bearing against the longitudinal flange without being attached to the segment; the upper segments, however, were, as shown in [ Fig. 2, Plate XXXVIII], and [Fig. 1, Plate XLI], attached to the erector, by using the expanding bar and the erector head designed by Mr. Patrick Fitzgerald, the Tunnel Superintendent. This was found to be a most convenient arrangement.

The single erector attached to the center of the shield was able to erect the iron as fast as it could be brought into the tunnel, and even when the weight of the segments was increased 25% (from 2,060 to 2,580 lb.) it always proved equal to its task, although occasionally one of the chains in the mechanism broke and delayed the work for an hour or so; but the sum of all the delays from this cause and from breaks and leaks in the hydraulic line only averaged 13 min. per ring. The operating valve which was first used was a four-spindle turning valve, but this was replaced by a sliding valve which was found to be much more satisfactory, both in ease of operation and freedom from failure.

As the iron was put into place, two of the middle bolts in each longitudinal flange and two in each circumferential one were pulled as tight as possible, and the others put in loosely; then, as soon as the ring was in position, as large a force as could be conveniently worked at one time was engaged in tightening the bolts. The shape of the tunnel depended on the thoroughness of the tightening of the bolts, and the shield was never shoved until the bolts in all the longitudinal flanges had been thoroughly tightened. In addition, all the bolts in the circumferential flanges below the axis were tightened, and at least three of the six in each segment above. After the shield had been shoved ahead, the bolts were found to have slackened, and, where the daily progress was four rings, or more, it was necessary to have a small gang of men always at this work.

PLATE XL.
TRANS. AM. SOC. CIV. ENGRS.
VOL. LXVIII, No. 1155.
HEWETT AND BROWN ON
PENNSYLVANIA R. R. TUNNELS: NORTH RIVER TUNNELS.

In order to get at the bolts, special platforms were necessary, and throughout the greater part of the work, a traveling platform was used. This enabled the men to reach handily all parts of the seven leading rings. This platform was supported and moved forward on wheels fixed on brackets to the tunnel, and was pulled forward by connecting chains every time the shield was shoved. In the early part of the work it was not possible to use platforms, because, in order to maintain the correct circular shape of the iron lining, it was necessary to put in temporary horizontal turnbuckles at axis level. These, however, were very convenient for supporting the planks which were used as a temporary bolting platform for the sides of the tunnel, and a temporary platform resting on 6 by 6-in. timbers across the tunnel enabled the bolts in the crown of the tunnel to be reached, while the 6 by 6-in. timbers were left in to support the emergency platform previously described ([Plate XL]), which extended the entire length of the tunnel.

The time taken to erect the iron lining became shorter and shorter as the tunnel organization became more perfect and the force better trained, so that, whereas, in the early part of the work, it frequently took 6 hours to erect a ring, in the latter part, when the work was nearing completion, it was a common occurrence to erect a ring in 30 min. The average time in the "heavy iron" section, which included the greater part of the work under the river, was 1 hour 4 min. for the erection of the ring and 40 min. for tightening the bolts after that had been completed, so that the total time spent by the whole gang on erection and bolting averaged 1 hour 44 min. per ring, exclusive of the time spent by the small gang which was always engaged in tightening the bolts. The average time spent in erecting and bolting, for the whole length of the tube tunnels, was 2 hours 15 min. per ring.

Tables of Progress.—[Tables 24], [25], [26], and [27] have been prepared to show the time taken in the various operations at each working face.

In [Tables 24], [25], [26], and [27], the following symbols are used:

A—Including assistant superintendents, foremen, and electricians, in driving the shield, erecting iron, mucking, attending to the electric lights, and repairing the pipe line.

B—Drillers, drillers' helpers, drill foremen, and nippers.

C—All men grouting.

D—Engineers and laborers wholly employed on transport between the first lock and the face.

E—In rock, one car = 0.60 cu. yd.; in sand or silt = 1.20 cu. yd. in place.

F—Time between completion of mucking and putting in first plate, spent in shoving the jacks back.

G—In ordinary iron = the whole time spent on erection and bolting. In heavy iron = the time between putting in the first plate and placing the key only.

H—Time between placing the key and starting the next shove, spent by the whole gang in tightening bolts. In addition to this, there was a small gang which spent its whole time at this work.

I—In [Table 24] the first pair of bore segments is at ring 207-208.
In [Table 25] the first pair of bore segments is at ring 201-202.
In [Table 26] the first pair of bore segments is at ring 185-186.
In [Table 27] the first pair of bore segments is at ring 171-172.
Outside diameter of tunnel = 23 ft. 0 in.
Inside diameter of tunnel = 21 ft. 2 in.
Length of ring = 2 ft. 6 in.

In the "Ordinary Iron" section the time is divided between mucking (which included the shoving and pushing back of the jacks) and the erection time (which included the time spent by the whole gang in tightening bolts). In the "Heavy Iron" section these times are all separated into "Mucking," "Pushing Back Jacks," "Erecting," and "Bolting," and here the bolting time included only that spent on bolts by the whole gang; in addition, there was a small gang engaged solely in tightening bolts. The lost time is the average time lost due to the break-down of hydraulic pipe lines, damaged jacks, and broken erector chains. The erection time is separated for the various kinds of rings, that is, straight ordinary rings, rings containing No. 1 bore segments, rings containing No. 2 bore segments, and taper rings, and it will be seen that, on the average, taper rings took 22 min. (or 24%) more time to erect and to bolt than ordinary ones, and that rings containing No. 2 bore segments took 14 min. (or 15%) more.

PLATE XLI.
TRANS. AM. SOC. CIV. ENGRS.
VOL. LXVIII, No. 1155.
HEWETT AND BROWN ON
PENNSYLVANIA R. R. TUNNELS: NORTH RIVER TUNNELS.

TABLE 24.— Shield-Driven Tunnel Work, Manhattan Shaft, River Tunnel North. Table showing the size of the gang, the amount of excavation, and the time per ring taken for the various operations involved in building tunnel through the several kinds of ground encountered; also the extent and nature of all the unavoidable delays.

Weight of iron	Section between rings	Description				Ave. No. of Men					Av. No. of cu. yd. per ring	Time Mucking per cu. yd.	Av. Time per ring, shoving and Mucking	Time for Jacks	Time for Ring Erection, Hrs. and Min.					Bolting Time, Whole Time on Bolts After Ring is Complete.					Time lost repairing hydraulic piping	Total Time.
		Length in feet	Material	Ave air Pressure	Method of Excavation	Shield	Drilling	Grouting	Air trans	Total					Ordinary	Bore 1	Bore 2	Taper	Mean	Ordinary	Bore 1	Bore 2	Taper	Mean		Ordinary	Bore 1	Bore 2	Taper	Mean
						A	B	C	D		E			F	G	G	G	G	G	H	H	H	H	H
Ordinary	1-54	135.0	Rock	0	[P]					14				Time for jacks for light iron is included in shoving and mucking	4-00			4-21	4-04	Excavation partially completed previously.
	55-80	65.0	"	19	[P]	24	7	⅓	1	32	41	0-31	21-00		6-04			5-30	5-57	}	Bolting time for light iron is included in erection.			{		27-4			26-30	26-57
	81-107	65.0	Soft rock	18	[P]	22	5		2	29	41	0-33	22-30		4-26				4-26	}				{		26-56				26-56
	108-153	117.5	Rock	14	[P]	17	11		2	30	41	0-39	26-31		3-10			3-30	3-12	}				{		29-41			30-1	29-43
	154-194	102.5	Rock and earth	14	[P]	23	6		2	31	41	0-27	18-34		2-08	J.	J.	2-40	2-10	}				{		20-42			21-14	20-44
	195-215	52.5	Silt	19	[P]Breasting	28			2	30	41	0-10	6-46		3-03	3-30	3-30		3-09	}				{		9-49	10-16	10-16		9-55
	216-393	445.0	"	20	[Q]8 doors	27			4	31	46	0-05	3-53		2-40	2-56	3-00	3-10	2-50	}				{	0-09	6-42	6-58	7-02	7-12	6-52
	394-429	90.0	Silt, piles, rip-rap	24	[P]Breasting	28			4	32	46	0-18	17-09		3-43	3-39	4-46	4-11	3-56	}				{		23-79	23-25	24-32	23-57	23-42
	430-509	200.0	Silt	23	[Q]1 door	24			3	27	11	0-10	1-42		3-14	4-12	3-59	3-46	3-34	}				{	0-18	5-14	6-12	5-59	5-46	5-34
	510-692	457.5	"	23	[Q]3 doors	26			4	30	30	0-05	1-47		2-08	2-21	2-32	2-50	2-18	}				{	0-11	4-06	4-19	4-30	4-48	4-16
	55-692	1,593.0		20		25	2		3	30	30	0-15	7-35	[N]	3-02			4-31	3-12	}				{	0-17	10-54			12-23	11-04
	216-692	1,192.5		22		26			4	30	30	0-07	3-42	[N]	2-38	2-59	3-08	1-30	2-50	}				{	0-25	6-45	7-06	7-15	5-37	6-57
Heavy	693-954	655.0	Silt	24	[Q]1 door	28			6	34	11	0-12	1-02	[N]	1-52	2-05	2-15	2-29	2-0	}				{	0-13	3-7	3-20	3-30	3-44	3-15
	955-1,014	150.0	"	24	[Q]1 "	28			8	36	12	0-04	0-48	0-16	0-51	1-18	1-08	0-50	0-58	0-24	0-21	0-37	0-10	0-25	0	2-19	2-43	2-49	2-04	2-27
	1,015-1,074	150.0	"	24	[Q]1 "	25			8	33	12	0-03	0-41	0-13	0-43	0-46	0-55	0-40	0-45	0-31	0-30	0-52	0-23	0-34	0-02	2-10	2-12	2-43	1-59	2-15
	1,075-1,134	150.0	"	24	[Q]1 "	27			9	36	8	0-04	0-34	0-12	1-04	1-01	1-15	1-20	1-08	0-28	0-35	1-40	0-52	0-44	0-03	2-21	2-25	3-44	3-01	2-41
	1,135-1,194	150.0	"	25	[Q]1 "	26			8	34	8	0-04	0-33	0-13	0-53	0-51	0-58	0-46	0-53	0-32	0-20	0-24	0-18	0-26	0	2-11	1-57	2-08	1-50	2-05
	1,195-1,224	75.0	"	25	[Q]1 "	24			9	33	6	0-04	0-24	0-12	0-58	0-42	0-53	0-50	0-54	0-19	0-20	0-34	0-35	0-23	0	1-53	1-38	2-03	2-01	1-53
	1,225-1,262	95.0	"	25	[Q]1 "	23			9	32	5	0-05	0-23	0-10	0-48	0-49	0-50	0-35	0-47	0-29	0-29	0-36	0-18	0-30	0	1-50	1-51	1-59	1-26	1-50
	1,263-1,277	37.5	"	25	[Q]1 "	24			10	34	10	0-04	0-36	0-11	0-47	0-50	0-52	0-48	0-52	0-23	0-23	0-41	0-23	0-27	0	1-57	2-0	2-20	1-58	2-06
	1,278-1,307	75.0	"	25	[Q]1 "	21			10	31	17	0-04	1-09	0-10	1-03	1-01	1-06	0-00	1-04	0-33	0-34	0-51	0-0	0-36	0	2-55	2-54	3-16	0-0	2-59
	1,308-1,326	47.5	"	28	[Q]1 "	27			11	38	22	0-05	1-39	0-18	1-25	1-48	1-50	0-50	1-31	0-49	0-42	0-58	0-25	0-48	0	4-11	4-27	4-45	3-12	4-16
	955-1,326	930.0		24		26			9	35	11	0-04	0-41	0-13	0-55	0-59	1-03	0-55	0-58	0-29	0-27	0-49	0-31	0-32	0	2-18	2-20	2-46	2-20	2-24
	693-1,326	1,585.0		24		27			8	35	12	0-04	0-51	[N]	1-27	1-34	1-41	1-38	1-31	[O]					0-06	2-24	2-31	2-38	2-35	2-28
All	216-1,326	2,777.5		23		27			7	34	19	0-06	1-59	[N]	1-55	2-08	2-16	1-35	2-03	[O]					0-16					4-18
	55-1,326	3,180.0		22		26			6	32	21	0-10	4-13	[N]					2-22	[O]					0-12					6-47

SUMMARY

Weight of iron	Section between rings	Description				Ave. No. of Men in Gang					Average No. of cubic yard per ring	Time mucking, per cubic yard	Average Time per Ring				Unavoidable Delays (Not Included in Average Time per Ring).
		Length in feet	Material	Ave. air Pressure	Method of Excavation	Shield	Drilling	Grouting	Air Trans	Total			Shoving and mucking[N]	Erection[O]	Lost time	Total	Items	Time hrs--min
Ordinary	1-54	135.0	Rock	0	[P]					14				4-14			First bulkhead	172-00
	55-194	350.0	Earth and rock	16	[P]	22	6	⅓	2	30	41	0-32	21-44	4-04		25-48	Second bulkhead	119-00
	195-393	497.5	Silt	20	[P]Breasting	27			4	31	38	0-07	4-11	2-52	0-09	7-12	Grouting	200-00
	394-440	117.5	"	24	[P]Breasting	28			4	32	41	0-18	11-54	4-17	1-41	17-52	Blowout	73-00
	441-692	630.0	"	23	[Q]3 doors	25			4	29	17	0-06	2-04	2-34	0-42	5-20	Cradle	100-00
	216-692	1,192.5		22		26			4	30	30	0-07	3-42	2-50	0-25	6-57	Total	664-00
	55-692	1,595.0		20		25	2		3	30	30	0-15	7-35	3-12	0-17	11-04	Per ring	0-39
Heavy	693-1,326	1,585.0	Silt	24	[Q]1 door	27			8	35	12	0-04	0-51	1-31	0-06	2-28
All	55-1,326	3,180.0		22		26			6	32	21	0-10	4-13	2-22	0-12	6-47

[N] Including time for jacks.

[O] Including bolting time.

[P] Excavating ahead of shield.

[Q] Shoving shield into silt with ... doors open.

TABLE 25.— Shield-Driven Tunnel Work, Manhattan Shaft, River Tunnel South. Table showing the size of the gang, the amount of excavation, and the time per ring taken for the various operations involved in building tunnel through the several kinds of ground encountered; also the extent and nature of all the unavoidable delays.

Weight of iron	Section between rings	Description				Average No. of Men in Gang					Av. No. of cu. yd. per ring	Time Mucking, per cu. yd.	Av. time per ring shoving and Mucking	Time for Jacks	Time for Ring Erection, Hrs. and Min.					Bolting Time, Whole Time on Bolts After Ring is Complete.					Time lost repairing hydraulic piping	Total Time.
		Length in feet	Material	Ave air pressure	Method of Excavation	Shield	Drilling	Grouting	Air trans	Total					Ordinary	Bore 1	Bore 2	Taper	Mean	Ordinary	Bore 1	Bore 2	Taper	Mean		Ordinary	Bore 1	Bore 2	Taper	Mean
						A	B	C	D		E			F	G	G	G	G	G	H	H	H	H	H
Ordinary	1-68	170.0	Rock	0	[R]	20	5	5	2	32	41	0-14	9-53	Time for jacks for light iron is included in shoving and mucking	5-27			4-32	5-07	Excavation partially completed previously. Bolting time for light iron is included in erection.						15-20			14-25	15-00
	69-95	67.5	Rock and earth	13	[R]	22	8		2	32	41	0-24	16-18		3-02			2-40	3-00							19-20			18-58	19-18
	96-141	115.0	Rock	10	[R]	21	13		2	36	70	0-16	18-16		2-08			2-27	2-09						0-03	20-27			20-46	20-28
	142-191	125.0	Rock and earth	15	[R]	24	7		2	33	52	0-20	17-27		2-08	J	J	2-04	2-08						0-12	19-47			19-43	19-47
	192-203	30.0	Silt	18	[R]Breasting	23			3	26	36	0-13	7-58		2-27	6-00	2-10	3-15	2-47						1-20	11-45	15-18	11-28	12-33	12-05
	204-388	462.5	"	18	[S]7 doors	27			3	30	37	0-05	3-19		2-41	2-49	2-54	2-56	2-47						0-05	6-05	6-13	6-18	6-20	6-11
	389-429	102.5	Silt, piles and rip-rap.	22	[S] ]6 doors [ [R]Breasting	24			4	28	40	0-17	12-42		3-15	2-36	5-03	3-26	3-27						0-38	16-35	15-56	18-23	16-46	16-47
	430-504	187.5	Silt	21	[S]3 doors	23			5	28	20	0-06	1-51		2-53	3-17	3-00	2-57	2-59						0-39	5-23	5-47	5-30	6-27	5-29
	505-629	312.5	"	22	[ [S]4 doors	25			6	31	27	0-05	2-20		2-23	2-40	2-45	2-28	2-30						0-23	5-06	5-23	5-28	5-11	5-13
	630-692	157.5	"	23	[ [S]2 doors.	24			8	32	22	0-05	1-53		1-54	2-10	2-22	2-23	2-02						0-08	3-55	4-11	4-23	4-24	4-03
	204-692	1,222.5		21		25			5	30	30	0-07	3-27	[T]	2-34	2-45	2-58	2-35	2-42						0-18	6-19	6-30	6-43	6-20	6-27
	69-692	1,560.0		17		23	4	0	3	30	36	0-11	6-40	[T]	2-47			3-18	2-52						0-15	9-42			10-13	9-47
Heavy	693-766	185.0	Silt	24	[S]2 doors	21			6	27	22	0-05	1-35	0-25	1-18	1-44	1-30	1-40	1-25	0-43	1-09	0-52	0-50	0-49	0-07	4-08	5-00	4-29	4-37	4-21
	767-806	100.0	"	24	[ [S]2 "	22			7	29	22	0-05	1-19	0-21	1-00	0-56	1-37	1-21	1-08	0-38	0-24	0-43	0-38	0-42	0-02	3-20	3-02	4-02	3-41	3-32
	807-900	235.0	"	24	[ [S]1½ "	23			8	31	19	0-05	1-11	0-17	0-58	1-13	1-08	1-12	1-04	0-39	0-34	0-56	0-31	0-40	0-06	3-11	3-21	3-38	3-17	3-18
	901-933	82.5	"	25	[S]1 door	30			10	40	19	0-04	1-13	0-09	0-59	1-05	0-59		1-00	0-34	0-26	1-47		0-43	0-05	3-00	2-58	4-13		3-10
	934-988	137.5	"	25	[ [S]1 "	30			11	41	16	0-04	0-54	0-12	0-49	0-44	0-56		0-50	0-28	0-34	0-34		0-30	0-06	2-29	2-30	2-42		2-32
	989-1,043	137.5	"	25	[ [S]1 "	28			11	39	13	0-05	0-52	0-14	0-51	0-44	0-52	1-14	0-52	0-33	0-24	0-51	0-35	0-35	0-04	2-34	2-18	2-53	2-59	2-37
	1,044-1,053	25.0	"	26	[ [S]1 "	25			9	34	16	0-07	0-40	0-15	1-04	1-15	0-50	0-55	1-02	0-23	0-38	0-30	0-55	0-36		3-22	3-48	3-15	3-45	3-33
	1,054-1,068	37.5		26	[ [S]1 "	26			9	35	8	0-05	0-36	0-08	0-57	0-40	1-02		0-56	0-33	0-25	0-35		0-32		2-14	1-49	2-21		2-12
	1,069-1,110	105.0	"	26	[S]1 "	30			11	41	14	0-06	1-00	0-15	0-48	0-54	1-06	1-31	0-56	0-32	0-40	0-48	0-46	0-37	0-05	2-40	2-54	3-14	3-37	2-53
	693-1,110	1,045.0		25		25			8	33	18	0-05	1-29	[T]	1-01	1-08	1-09	1-19	1-05	0-37	0-39	0-52	0-40	0-40	0-05	3-12	3-21	3-35	3-33	3-19
All	204-1,110	2,267.5		23		25			6	31	25	0-06	2-35	[T]	2-09	2-19	2-33	2-19	2-17	[U]					0-12	4-56	5-06	5-20	5-06	5-04
	69-1,110	2,605.0		20		24	2		5	31	29	0-09	4-36	[T]	2-19			2-46	2-25	[U]					0-14	7--0			7-36	7-15

SUMMARY

Weight of iron	Section between rings	Description				Ave. No. of Men in Gang					Average No. of cubic yards per ring	Mucking, per cubic yard	Average Time per ring				Unavoidable Delays (not Included in Average Time per Ring).
		Length in feet	Material	Ave. air pressure	Mehod of Excavation	Shield	Drilling	Grouting	Air Trans	Total			Shoving and mucking[T]	Erection [U]	Lost time	Total	Items	Time hrs min
Ordinary	1-68	170.0	Rock	0	[R]	20	5	5	5	32	41	0-14	9-53	5-07		15-00	First bulkhead	160--00
	69-191	307.5	Rock and earth	13	[R]	22	9		2	33	54	0-19	17-20	2-26	0-05	19-51	Second bulkhead	157--45
	192-388	492.5	Silt	18	[R]Breasting [S]7 doors	25			3	28	37	0-09	5-39	2-47	0-63	9-29	Grouting	200--00
	389-429	102.5	Silt piles and rip-rap	22	[R] Breasting [S]6 doors	24			4	28	40	0-17	12-42	3-27	0-38	16-47	Blowout	69--45
	430-692	657.5	Silt	22	[S]3 doors	24			6	30	24	0-05	1-58	2-29	0-22	4-49	Waiting for heavy iron	64--0
	204-692	1,222.5		21		25			5	30	30	0-07	3-27	2-42	0-18	6-27	Total	715--30
	69-692	1,560.0		17		23	4	0	3	30	36	0-11	6-40	2-52	0-15	9-47	Per ring	0--39
Heavy	693-1,110	1,045.0		25	[S]1 door	25			8	33	18	0-05	1-29	1-45	0-06	3-19
All	69-1,110	2,605.0		20		24			5	31	29	0-09	4-36	2-25	0-14	7-15

[R] Excavating ahead of shield.

[S] Shoving shield into silt with ... doors open.

[T] Including time for jacks.

[U] Including bolting time.

TABLE 26.— Shield-Driven Tunnel Work, Weehawken Shaft, River Tunnel North. Table showing the size of the gang, the amount of excavation, and the time per ring taken for the various operations involved in building tunnel through the several kinds of ground encountered; also the extent and nature of all the unavoidable delays.

Weight of iron	Section between rings	Description				Ave. No. of Men in Gang					Av. No. of cu. yd. per ring	Time Mucking, per cu. yd.	Av. Time per ring, shoving and mucking	Time for Jacks	Time for Ring Erection, Hrs. and Min.					Bolting Time, Whole Time on Bolts After Ring is Complete.					Time lost repairing hydraulic piping	Total Time.
		Length in feet	Material	Ave air Pressure	Method of Excavation	Shield	Drilling	Grouting	Air trans	Total					Straight	Bore 1	Bore 2	Taper	Mean	Straight	Bore 1	Bore 2	Taper	Mean		Straight	Bore 1	Bore 2	Taper	Mean
						A	B	C	D		E			F	G	G	G	G	G	H	H	H	H	H
Ordinary	1-24	60.0	Rock	0	[X]	9	.04	0	0	10	46	0-06	4-32	Time for jacks for light iron is included in shoving and mucking.	6-23				6-23	Excavation partially completed previously.						10-55				10-55
	25-55	77.5	"	20	[X]	14	5	0.5	1	21	46	0-51	39-33		4-25			5-10	4-29							43-58			44-43	44-02
	56-72	42.5	Mixed sand and rock	10	[X]Breasting	22	2	.09	2	26	44	0-21	15-05		2-53	3-15			2-55						0-04	18-02			18-24	18-04
	73-165	232.5	Sand and gravel	10	[X] "	22	0	0.1	2	24	39	0-11	6-56		2-27			2-21	2-26	Bolting time for light iron is included in erection.					0-09	9-32			9-26	9-31
	166-184	47.5	Sand and silt with piles	20	[X] Breasting and cutting piles	22	0	.38	3	25	42	0-09	6-19		2-31	J	J	6-30	2-37						0-07	8-57			12-56	9-03
	185-253	172.5	Silt and piles	24		23	0	.71	3	26	43	0-09	6-13		1-57	2-44	2-52	2-00	2-15						0-15	8-25	9-12	9-20	8-28	8-43
	254-293	100.0	Silt	26	[Y]8 doors	22	0	0	3	25	6	0-18	1-45		1-58	1-57	2-15	2-45	2-02						0-14	3-57	3-56	4-14	4-44	4-01
	294-301	20.0	"	27		19	0	0	2	21	0	1-08			0-58	1-45	1-50		1-17							2-06	2-53	2-58		2-25
	302-307	15.0	"	27	[Y]8 doors	21	0	0	2	23	26	0-09	4-03		2-20	1-40	1-55	2-57	2-22							6-23	5-43	5-58	7-00	6-25
	308-342	87.5	"	28		19	0	0	2	21	0	0	0-36		2-00	1-34	2-42	1-58	2-02							2-36	2-10	3-18	2-29	2-38
	343-347	12.5	"	28	[Y]8 doors	15	0	0	2	17	2	0-36	1-11		2-15	2-20		2-43	2-33						0-39	4-05	4-10		4-43	4-23
	348-459	280.0	"	28		20	0	0	3	23	0	0	0-33		2-03	2-04	2-09	2-23	2-06						0-14	2-50	2-51	2-56	3-10	2-53
	460-494	87.5	"	28	[Y]8 doors	21	0	0	3	24	9	0-09	1-23		2-49	2-30	2-50	1-50	2-38						0-27	4-39	4-20	4-40	3-40	4-28
	495-513	47.5	"	28	8 "	23	0	0	4	27	17	0-05	1-28		2-35	2-23	1-55	2-10	2-26							4-03	3-51	3-23	3-38	3-54
	514-605	230.0	"	28	8 "	25	0	0	4	29	26	0-04	1-44		2-12	2-34	2-29	2-15	2-19							3-56	4-18	4-13	3-59	4-03
	606-624	47.5	"	28	8 "	24	0	0	4	28	16	0-04	1-07		1-54	2-33	2-16	1-35	2-04							3-01	3-40	3-23	2-42	3-11
	625-640	40.0	"	28	8 "	38	0	0	5	43	24	0-03	1-13		2-14	2-55	2-35	2-46	2-28							3-27	4-08	3-48	3-59	3-41
	25-640	1,540.0		20
	185-640	1,140.0		26		23	0	0.2	3	26	16	0-07	1-58	[V]	2-07	2-19	2-26	2-15	2-13						0-09	4-14	4-26	4-33	4-22	4-20
Heavy	641-647	17.5	Silt	28	[Y]8 doors	24	0	0	6	30	19	0-04	0-08	[V]	1-20	2-08	1-65	1-40	1-41	0-40	0-35	1-25	0-55	0-47		3-08	3-51	4-28	3-43	3-36
	648-751	260.0	"	28	[Y]8 "	22	0	0	4	26	14	0-03	0-36	0-12	1-21	1-22	1-26	1-55	1-23	0-31	0-29	0-38	0-30	0-32	0-12	2-52	2-51	3-04	3-25	2-55
	752-795	110.0	"	28	[Y]8 "	18	0	0	7	25	10	0-03	0-29	0-14	0-46	1-25	1-31	2-37	1-10	0-48	0-31	0-44	0-35	0-43	0-05	2-22	2-44	3-03	4-00	2-41
	796-825	75.0	"	28	[Y]8 "	19	0	0	10	28	5	0-08	0-40	0-11	0-48	1-31	1-34	0-53	1-03	0-31	1-03	0-49	3-27	0-51		2-10	3-25	3-14	5-11	2-45
	826-854	72.5	"	28	[Y]8 "	17	0	0	3	20	15	0-03	0-48	0-19	0-54	1-12	1-02	1-23	1-01	0-22	0-37	0-38	0-20	0-27	0-06	2-29	3-02	2-53	2-56	2-41
	855-881	67.5	"	28	[Y]8 "	23	0	0	9	32	7	0-05	0-33	0-16	0-59	0-45	1-15	1-20	1-01	0-22	0-21	0-45	0-40	0-26	0-45	2-55	2-40	3-34	3-34	3-01
	882-982	252.5	"	28	[Y]8 "	20	0	0	8	28	10	0-02	0-20	0-14	0-49	1-02	1-01	0-50	0-54	0-41	0-36	0-36	0-15	0-39	0-12	2-16	2-24	2-23	1-51	2-19
	983-990	20.0	"	28	[Y]8 "	21	0	0	7	28	17	0-02	0-34	0-14	0-40	0-40	0-48		0-44	1-15	0-15	0-28		0-48		2-43	1-43	2-04		2-20
	991-1,049	147.5	"	28	[Y]8 "	23	0	0	7	30	8	0-03	0-21	0-11	0-40	0-48	0-39		0-41	0-41	0-34	0-55		0-41		1-53	1-54	2-06		1-54
	1,050-1,074	62.5	"	28	[Y]8 "	24	0	0	9	33	7	0-03	0-18	0-10	0-43	0-44	0-46	0-40	0-43	0-35	1-15	0-07	0-35	0-48	0-04	1-50	2-31	2-25	1-47	2-03
	1,075-1,110	90.0	"	28	[Y]8 "	25	0	0	10	35	16	0-02	0-33	0-12	0-50	1-02	1-06	0-58	0-55	0-35	0-46	0-58	2-10	0-41	0-21	2-31	2-54	2-10	4-14	2-42
	641-1,110	1,175.0		28		21	0	0	7	28	8	0-04	0-30	0-14	0-56	1-08	1-12	1-29	1-02	0-36	0-36	0-44	0-54	6-38	0-11	2-27	2-27	2-51	3-18	2-35
All	185-1,110	2,315.0		28		22	0	0.1	5	27	12	0-07	1-20	0[V]	1-48	2-01	2-11	2-17	1-56	[W]					0-10	3-18	3-31	3-41	3-47	3-26
	25-1,110	2,715.0		26		21	0.1	0.1	3	24	17.1	0-12	3-13	[V]					2-05	[W]					0-09					5-27

SUMMARY

Weight of iron	Section between rings	Description				Average No. of Men in Gang					Average No. of cubic yards per ring	Time mucking, per cubic yard	Average Time per Ring.				Unavoidable Delays (not Included in Average Time per Ring).
		Length in feet	Material	Ave. air Pressure	Method of Excavation	Shield	Drilling	Grouting	Air trans	Total			Shoving and mucking [V]	Erection [W]	Lost time	Total	Items	Time hrs min
Ordinary	1-24	60.0	Rock	0	[X]	9	.04	0	0	10	46	0-06	4-32	6-23	0-00	10-55	First bulkhead	132-00
	25-55	77.5	"	20	[X]	14	5	0.5	1	21	46	0-51	39-33	4-29	0-00	44-02	Second bulkhead	158-50
	56-72	42.5	Mixed sand and rock	10	[X]Breasting	22	2	.09	2	26	44	0-21	15-05	2-55	0-04	18-04	Grouting	240-00
	73-165	232.5	Sand & gravel	10	[X]Breasting	22	0	.1	2	24	39	0-11	6-56	2-26	0-09	9-31	Old cave-in	234-00
	166-184	47.5	Sand and silt with piles	20	[X]Breasting and cutting piles	22	0	.38	3	25	42	0-09	6-19	2-37	0-07	9-03	Shoving tube	128-00
	185-253	172.5	Silt w/ piles	24	[X]Breasting and cutting piles	23	0	.71	3	26	43	0-09	6-13	2-15	0-05	8-43	-	-
	254-640	110.0	Silt	26	[Y]Doors	22	0	0	3	25	11	0-07	1-13	2-20	0-08	3-41	Total	892-50
	25-640	1,540.0		20	[Y]Doors	21	0.3	.12	3	24	24	0-14	5-06	2-24	0-08	7-38	per ring	0-49
Hvy	641-1,110	1,175.0		28		21	0	0	7	28	8	0-04	0-44	1-40	0-11	2-35
All	25-1,110	2,715.0		26		21	0.1	0.1	3	24	17.1	0-12	3-13	3-05	0-09	5-27

[V] Including time for jacks.

[W] Including bolting time.

[X] Excavating ahead of shield.

[Y] Shoving shield into silt with ... doors open.

TABLE 27.— Shield-Driven Tunnel Work, Weehawken Shaft, River Tunnel South. Table showing the size of the gang, the amount of excavation, and the time per ring taken for the various operations involved in building tunnel through the several kinds of ground encountered; also the extent and nature of all the unavoidable delays.

Weight of iron.	Section between rings.	Description.				Ave. No. of Men in Gang.					Av. No. of cu. yd. per ring.	Time Mucking, per cu. yd.	Av. Time per ring Shoving and Mucking.	Time for Jacks.	Time for Ring Erection, Hrs. and Min.					Bolting Time, (Whole Time on Bolts After Ring is Complete.)					Time lost repairing hydraulic piping.	Total Time.
		Length in feet.	Material.	Ave. air Pressure.	Method of Excavation.	Shield.	Drilling.	Grouting.	Air trans.	Total.					Straight.	Bore 1.	Bore 2.	Taper.	Mean.	Straight.	Bore 1.	Bore 2.	Taper.	Mean.		Straight.	Bore 1.	Bore 2.	Taper.	Mean.
						A	B	C	D		E			F	G	G	G	G	G	H	H	H	H	H
Ordinary.	1-27	67.5	Rock	9	[B]	Excavation partially completed previously.									8-30			3-45	8-08	Bolting time for light iron is included in erection.					0-14	21-11			16-26	20-49
	28-42	37.5	"	12	[B]	13	4	1	1	19	48.7	0-25	20-33		4-23			4-00	4-21						0-12	25-08			24-45	25-06
	43-58	40.0	Rock or gravel	12	[B]	19	2	2	2	25	44.2	0-46	33-44		4-16			5-45	4-44						1-15	39-15			40-44	39-43
	59-153	237.5	Gravel and sand	16	[B]Breasting	25		1	4	30	39.0	0-12	8-06		2-19			4-18	2-23						0-30	10-55			12-54	10-59
	154-170	42.5	Sand and silt with piles	18	"	26		1	5	32	41.6	0-10	7-10		2-00	J.	J.	1-48	1-59						0-00	9-10	J.	J.	8-58	9-09
	171-236	165.0	Silt with piles	22	Top half	22		1	3	26	42.6	0-10	7-23		2-36	2-55	2-58	1-24	2-35						0-05	10-04	10-23	10-26	8-52	10-03
	237-259	57.5	Silt	25	[C]1 door	18		1	3	22	13.8	0-11	2-29		3-01	2-05	1-28	2-00	2-32						0-20	5-50	4-54	4-17	4-49	5-21
	260-302	107.5	"	27	[C]1 door	15			2	17	0		0-32		2-34	2-35	3-38	4-28	3-05						0-08	3-14	3-15	4-18	5-08	3-45
	303-350	120.0	"	27	[C]8 doors	15			4	19	6.9	0-07	0-52		2-59	2-28	2-37	1-44	2-41						0-07	3-58	3-27	3-36	2-43	3-40
	351-378	70.0	"	27.5	[C]8 "	18			6	24	0		0-33		2-05	2-32	2-48	2-00	2-18						0-17	2-55	3-22	3-38	2-50	3-08
	379-424	115.0	"	27.5	[C]8 "	19			4	23	6.9	0-07	0-48		3-34	2-51	3-18	3-19	3-22						0-25	4-47	4-09	4-31	4-32	4-35
	425-522	245.0	"	28	[C]1 door	19			4	23	6.7	0-06	0-45		3-09	3-51	3-00	3-28	3-16						0-16	4-10	4-52	4-01	4-29	4-17
	523-625	257.5	"	28	[C]1 "	20			4	24	0		0-32		1-36	1-37	1-47	1-51	1-39						0-12	2-20	2-21	2-31	2-35	2-23
	171-625	1,137.5		27		19			4	23	9.7	0-11	1-44	[Z]	2-37	2-41	2-41	2-32	2-38						0-13	4-34	4-38	4-38	4-29	4-35
	28-625	1,495.0		25		19	.8	0.8	3.4	24	17.8	0-14	4-14	[Z]					2-41						0-16					7-11
Heavy.	626-649	57.5	Silt	28	[C]1 door	16			3	19	12.2	0-12	2-23	[Z]	2-19	2-30	2-05	1-42	2-16	1-01	1-04	1-04	0-50	1-01	0-32	6-15	6-29	6-04	5-27	6-12
	650-733	210.0	"	28	[C]8 doors	19			4	23	13.5		0-57	0-13	1-42	1-24	1-47	1-48	1-39	1-15	0-52	0-55	0-42	1-07	0-32	4-39	3-58	4-24	4-12	4-28
	734-753	50.0	"	28	[C]8 "	24			5	29	8.3	0-05	0-41	0-17	1-06	1-55	0-38	1-20	1-12	0-38	0-44	1-13	0-20	0-44	0-06	2-48	3-43	2-55	2-44	3-00
	754-844	227.5	"	28	[C]8 "	26			8	34	12.8	0-04	0-51	0-16	1-19	1-41	1-52	0-50	1-29	0-39	0-50	0-54	0-40	0-44	0-25	3-30	4-08	4-18	3-02	3-45
	845-859	37.5	"	28	[C]8 "	27			9	36	5.6	0-07	0-39	0-19	1-24	1-08	1-10		1-20	0-45	0-15	0-15		0-37	0-48	3-55	3-09	3-11		3-43
	860-899	100.0	"	28	[C]8 "	24			8	33	16.5	0-02	0-39	0-13	1-00	1-05	1-13		1-04	0-59	0-32	0-49		0-52	0-07	2-58	2-36	3-01		2-55
	900-935	90.0	"	28	[C]1 door	25			7	32	11.5	0-03	0-29	0-14	0-47	1-13	0-52	1-10	0-52	0-39	0-43	0-32	0-20	0-38	0-04	2-18	2-43	2-11	2-17	2-17
	936-963	70.5	"	28	[C]1 "	25			8	33	5.9	0-03	0-19	0-15	0-59	0-47	0-55		0-56	0-34	0-16	0-41		0-32	0-37	2-44	2-14	2-47		2-39
	964-1,003	100.0	"	28	[C]1 "	25			10	35	8.1	0-03	0-27	0-10	0-51	0-52	1-05		0-53	0-32	0-45	0-37		0-35	0-16	2-16	2-30	2-35		2-21
	1,004-1,060	142.5	"	28	[C]1 "	26			10	36	8.7	0-03	0-30	0-15	1-01	1-09	1-05	0-45	1-03	0-54	0-37	0-49	0-40	0-49	0-24	3-04	2-55	3-03	2-34	3-01
	1,061-1,110	125.0	"	28	[C]1 "	37			10	47	6.2	0-03	0-19	0-10	0-42	0-49	0-54	0-45	0-45	0-24	0-26	0-39	0-25	0-27	0-00	1-35	1-44	2-02	1-39	1-41
	1,111-1,238	320.0	"	28	[C]1 "	30			9	39	15.6	0-02	0-38	0-16	0-48	1-06	1-04	1-23	0-56	0-36	0-34	0-57	1-12	0-41	0-02	2-20	2-36	2-57	3-31	2-33
	1,239-1,312	185.0	"	28		39			9	38	13.0	0-03	0-36	0-18	1-04	1-01	1-02	1-15	1-07	0-39	0-43	1-12	0-59	0-50	0-10	2-47	2-48	3-18	3-18	3-01
	626-1,312	1,717.5	"	28		35			8	33	10.6	0-04	0-42	0-14	1-06	1-15	1-16	1-18	1-10	0-45	0-40	0-52	0-54	0-47	0-16	3-03	3-07	3-20	3-24	3-09
All	171-1,312	2,855.0		28		23			6	29	10.2	0-07	1-15	[ [Z]	2-09	2-13	2-21	2-20	2-13	[A]					0-15	3-39	3-43	3-51	3-50	3-43
	28-1,312	3,212.5		26		21			5	26	14.1	0-10	2-28	[Z]					2-18	[A]					0-15					5-01

SUMMARY

Weight of iron.	Section between rings.	Description.				Ave. No. of Men in Gang.					Average No. of cubic yards per ring.	Time mucking, per cubic yard.	Average Time per Ring.				Unavoidable Delays (not Included in Average Time per Ring).
		Length in feet.	Material.	Ave. air Pressure.	Method of Excavation.	Shield.	Drilling.	Grouting.	Air Trans.	Total.			Shoving and mucking. [Z]	Erection.[A]	Lost time.	Total.	Items.	Time, hrs. min.
Ordinary.	28-42	37.5	Rock	12	[B]Breast	13	4	1	1	19	48.7	0-25	20-33	4-21	0-12	25-06	First bulkhead	80-00
	43-58	40.0	Rock and gravel	12	"	19	2	2	2	25	44.2	0-46	33-44	4-44	1-15	39-43	Second bulkhead	156-00
	59-153	237.5	Gravel and sand	16	"	25		1	4	30	39.0	0-12	8-06	2-23	0-30	10-59	Grouting rock sections	280-00
	154-170	42.5	Sand or silt, with piles	18	"	26		1	5	32	41.6	0-10	7-10	1-59	0-0	9-09	Blow-outs	222-00
	171-236	165.0	Silt with piles	22	"	22		1	3	26	42.6	0-10	7-23	2-35	0-05	10-03	Shield repairs	326-40
	237-259	57.5	Silt	25	[C]1 door	18		1	3	22	13.8	0-11	2-29	2-32	0-20	5-21	Horz. timbers	69-30
	260-625	915.0	"	27	1 "	18			4	22	3.6	0-06	0-40	2-39	0-14	3-33	Total	1,134-10
	28-625	1,495.0		25		19	.8	0.8	3.4	24	17.8	0-14	4-14	2-41	0-16	7-11	Per ring	0-53
Heavy.	626-1,312	1,717.5	Silt	28		25			8	33	10.6	0-4	0-56	1-57	0-16	3-09
All.	28-1,312	3,212.5		26		21			5	26	14.1	0-10	2-28	2-18	0-15	5-01

[Z] Including time for jacks.

[A] Including bolting time.

[B] Excavating ahead of shield.

[C] Shoving shield into silt with ... doors open.

The average time taken for each operation at all the working faces is given in [Table 28]. The work has been subdivided into the different kinds of ground encountered.

The progress, as shown by the amount of work done each month by each shield, is given in [Table 29].

TABLE 28. —Shield-Driven Tunnel Work.—Total Number of Rings Erected and Shifts Worked by All Four Shields in Contracts Gy-West and Gj, and the Average Size of Gang, Amount of Excavation and Time Taken per Ring for the Various Operations Involved in Building Tunnel in Each of the Several Kinds of Ground Encountered; Also the Extent and Nature of All the Unavoidable Delays.

Weight of iron.	Description of Material.	Total No. of rings.	Total No. of feet.	Total number of 8-hour shifts.	Average air pressure.	Ave. No. of Men in Gang.					Cu. yd. per ring.	Time per cu. yd.	Average Time per Ring.				Ave. Unavoidable Delay per Working Face.
						Shield.	Drilling.	Grouting.	Air trans.	Total.			Shoving and mucking.	Erecting.	Lost time.	Total.	Items not included in previous figures.	Time.
											Unit.	Unit.	Hrs. Min.	Hrs. Min.	Hrs. Min.	Hrs. Min.		Ave. unit.
						Unit.	Unit.	Unit.	Unit.	Unit.			K	L	M			Hrs. Min.
Ordinary	Rock.	165	412.5	597	16	18	9	0.25	1	28	51	0-27	25 15	3 41	0 02	28 58	1st Bulkhead	136 00
	Rock and earth and rock and gravel.	177	442.5	500	14	22	5	0.3	2	30	45	0-26	19 31	2 55	0 11	22 37	2d "	147 54
	Sand and gravel (unobstructed), NJ	188	470.0	241	13	24		0.6	3	27	39	0-12	7 31	2 24	0 20	10 15	Grouting	246 00
	Sand and silt (with piles.)	171	427.5	199	22	23		1.0	3	27	43	0-09	6 46	2 24	0 09	9 19	Blow-outs	91 11
	Silt under R. R. tracks, NY	396	990.0	355	19	27			3	30	42	0-06	4 09	2 51	0 10	7 10	Miscellaneous	230 33
	Rip-rap and silt under bulkhead.	77	192.5	193	23	26			4	30	43	0-21	14 47	3 41	1 34	20 02	Total	851 38
	Total mixed and difficult ground.	1,174	2,935.0	2,085	17	22	4	0.3	3	29	43	0-18	11 02	2 54	0 16	14 12
	Silt--ordinary iron	1,302	3,255.0	676	25	22			4	26	12	0-07	1 20	2 35	0 14	4 12
Heavy	Silt--heavy iron.	2,209	5,522.5	791	26	25			8	33	12	0-05	0 58	1 44	0 10	2 52
	Silt--ord and heavy iron under river.	3,511	8,777.5	1,467	26	24			6	30	12	0-06	1 09	2 05	0 12	3 26
	Grand total.	4,685	11,712.5	3,552	21	23	2	0.2	4	29	20	0-11	3 33	2 15	0 13	6 01

Average delay per ring—0 hrs. 44 min.
Average rings built by one shield = 1,146¼.

Average time per ring.	6 hr 01 min
Delays.	44 min
	—————
Total time per ring.	6 hr 45 min

Note.—The "unavoidable delays" included in this table do not embrace the periods during which the work was at complete or partial standstill due to experiments and observations, shortage of iron due to change of design, and holidays.

K-Including time for jacks.
L-Including time spent by the whole gang on bolting; in addition to this there was a small gang which spent its whole time bolting.
M-Chiefly due to breakdowns of hydraulic lines and erector.

Air Pressure.—The air pressure varied from 17 to 37 lb. Behind the river line it averaged 17 lb. and under the river 26 lb. Behind the river lines the pressure was generally kept about equal to the water head at the crown, except where at Weehawken, as previously described, this was impossible.

In the silt the pressure was much lower than the hydrostatic head at the crown, but if it became necessary to make an excavation ahead of the shield, for example at the junction of the shields, the air pressure required was about equal to the weight of the overlying material, namely, the water and the silt, as the silt, which weighed from 97 to 106 lb. per cu. ft. and averaged 100 lb. per cu. ft., acted like a fluid.

TABLE 29.— Monthly Progress of Shield-Driven Tunnel Work.

Month	North Manhattan.				South Manhattan.				North Weehawken.				South Weehawken.				Average progress per shield lin. ft. per month.
	Number of rings erected.		Station of leading ring.	Lin. ft. for month.	Number of rings erected.		Station of leading ring.	Lin. ft. for month.	Number of rings erected.		Station of leading ring.	Lin. ft. for month.	Number of rings erected.		Station of leading ring.	Lin. ft. for month.
	For month.	To date.			For month.	To date.			For month.	To date.			For month.	To date.
1905
May	26	26	200 + 83.7	63.7													15.9
June	26	52	201 + 49.0	65.3					24	24	260 + 76.6	59.3	12	12	260 + 70.0	30.0	38.6
July	28	80	202 + 19.2	70.2					12	36	260 + 46.6	30.0	15	27	260 + 32.4	37.6	34.4
Aug	26	106	202 + 84.3	65.1					15	51	260 + 09.1	37.5	16	43	260 + 07.4	25.0	31.9
Sept	21	127	203 + 36.8	52.5	31	31	200 + 96.4	76.4	1	52	260 + 06.6	2.5	18	61	259 + 47.2	60.2	47.9
Oct	25	152	203 + 99.4	63.6	45	76	202 + 09.2	112.8	10	62	259 + 81.5	25.1	20	81	258 + 97.2	50.0	62.9
Nov	31	183	204 + 76.9	77.5	31	107	202 + 86.5	77.3	29	91	259 + 09.0	72.5	39	120	257 + 99.7	97.5	81.2
Dec	59	242	206 + 24.6	147.7	34	141	208 + 71.8	85.3	46	137	257 + 94.0	115.0	77	197	256 + 07.1	192.6	135.1
1906
Jan	94	336	208 + 59.8	235.2	27	168	304 + 39.4	67.6	77	214	256 + 01.4	192.6	73	270	254 + 24.6	182.5	169.4
Feb	78	414	210 + 54.9	195.1	64	232	205 + 99.6	160.2	133	347	252 + 68.6	332.8	165	435	250 + 11.7	412.9	275.2
Mar	56	470	211 + 95.2	140.3	96	328	208 + 39.9	240.3	142	489	249 + 13.3	355.3	111	546	247 + 34.0	277.7	253.4
April	119	589	214 + 93.0	297.8	84	412	210 + 59.1	210.2	32	521	248 + 33.3	80.0	78	624	245 + 38.9	195.1	195.7
May	129	718	218 + 15.7	322.7	70	482	212 + 25.3	165.2	121	642	245 + 30.6	302.7	2	626	245 + 33.9	5.0	198.9
June	218	936	232 + 60.9	545.2	140	622	215 + 75.5	350.2	162	804	241 + 25.3	405.3	157	788	241 + 41.1	392.8	423.4
July	155	1,091	227 + 48.5	387.6	82	704	217 + 80.7	205.2	113	917	238 + 42.4	282.9	118	901	238 + 45.9	295.2	292.7
Aug	145	1,236	231 + 11.2	362.7	134	838	221 + 15.8	335.1	138	1,055	234 + 97.1	345.3	140	1,041	234 + 95.8	850.1	348.3
Sept	89	1,325	233 + 34.1	222.9	168	1,006	225 + 35.8	420.0	55	1,110	233 + 59.5	137.6	177	1,218	230 + 52.8	443.0	305.9
Oct					105	1,111	227 + 98.6	262.8	1	1,111	233 + 57.0	2.5	94	1,312	228 + 16.8	236.0	125.3
Nov					7	1,118	228 + 16.8	18.2	9	1,120	233 + 34.1	22.9					10.3

A ½-in. air line was taken direct from the working chamber to the recording gauges in the engine-room, which enabled the engine-room force to keep a constant watch on the air conditions below. To avoid undue rise of pressure, a safety valve was set on the air line at each lock, set to blow off if the air pressure rose above that desired. The compressor plant was ample, except, as before described, when passing the gravel section at Weehawken.

Records were kept of the air supply, and it may be said here that the quantity of free air per man per hour was in general between 1,500 and 5,000 cu. ft., though in the open gravel where the escape was great it was for a time as much as 10,000 cu. ft. For more than half the silt period it was kept between 3,000 and 4,000 cu. ft., but when it seemed proved beyond doubt that any quantity more than 2,000 cu. ft. had no beneficial effect on health, no attempt was made to deliver more, and on two separate occasions for two consecutive weeks it ran as low as 1,000 cu. ft. without any increase in the number of cases of bends.

The amount of CO₂ in the air was also measured daily, as the specifications called for not more than 1 part of CO₂ per 1,000 parts of air. The average ranged between 0.8 and 1.5 parts per 1,000, though in exceptional cases it fell as low as 0.3 and rose to 4.0. The air temperature in the tunnels usually ranged from 55° to 60° Fahr., which was the temperature also of the surrounding silt, though at times, in the earlier parts of the work when grouting extensively in long sections of the tunnel in rock, it varied from 85° to 110° Fahr.

Grouting.—Grout of one part of Portland cement to one part of sand by volume was forced outside the tunnel lining by air pressure through 1½-in. tapped and plugged grout holes formed in each segment for this purpose, wherever the ground was not likely to squeeze in upon the metal lining as soon as this was erected. That is to say, it was used everywhere up to the river line; between river lines it was not used except at the New York bulkhead wall in order to fill voids in the rip-rap, and at the point of junction of the shields where the space between the metal lining and the shield skins outside it was grouted. Cow Bay sand was used, and it had to be screened to remove particles greater than 1/10 in. in diameter, which would choke the valves. For later grouting work, namely, in the top of the concrete lining inside the metal lining, Rockaway Beach sand was used. This is very fine, and did not need screening; it cost more, but the saving of screening and the non-blocking of valves, etc., resulted in a saving.

The grout was mixed in a machine shown in [Fig. 2, Plate XLI], which is a view of the grouting operation.

The grout pipes were not screwed directly into the tapped hole in the segments, but a pipe containing a nipple and valve was screwed into the grout hole and the grout pipe screwed to the pipe. This prevented the waste of grout, enabled the valve to be closed and the grout pipe disconnected, and the pipe to be left in position until the grout had set. In the full rock section, 20 or 30 rings were put in without grouting; then the shield was stopped, the last two or three rings were detached and pulled ahead by the shield, a masonry stop-wall was built around the outside of the last ring left in, and the whole 20 or 30 rings were grouted at one time. In the landward silt and gravel each ring had to be grouted as soon as the shield had left it, in order to avoid the flattening caused by the weight coming on the crown while the sides were as yet unsupported. The grout was prevented from reaching the tail of the shield by plugging up the space with empty cement bags, assisted by segmental boards held against the face of the leading ring by U-shaped clamps, fitting over the front circumferential flange of the ring and the boards, and tightened by wedges. The air pressure varied between 70 and 100 lb. per sq. in. above normal.

The force consisted of one pipe-fitter and one or two laborers employed part of their time. When a considerable length was being grouted at a time, as in the full rock section, many laborers were employed for a short period.