PART 2

====+====+=======+========+=======+=======+=============+========| | | | | | | | | | | | | | | | | | | | | | | | AVE. UNAVOIDABLE | | | | DELAY PER | | | AVERAGE TIME PER RING. | WORKING FACE. | Cu. |Time|------------------------+-------+-------------+--------| yd. |per |Shoving| | | | | Time | per |cu. | and | | Lost | | Items |--------| ring|yd. |mucking|Erecting| time | Total |not included |Ave unit| ----+----+-------+--------+-------+-------| in previous |--------| Unit|Unit|Hrs Min|Hrs Min |Hrs Min|Hrs Min| figures |Hrs Min | | | K | L | M | | | | ----+----+-------+--------+-------+-------+-------------+--------| 51 |0-27| 25 15| 3 41 | 0 02| 28 58|1st Bulkhead |136 00 | 45 |0-26| 19 31| 2 55 | 0 11| 22 37| 2d " |147 54 | | | | | | | | | 39 |0-12| 7 31| 2 24 | 0 20| 10 15|Grouting |246 00 | | | | | | | | | 43 |0-09| 6 46| 2 24 | 0 09| 9 19|Blow-outs | 91 11 | | | | | | | | | 42 |0-06| 4 09| 2 51 | 0 10| 7 10|Miscellaneous|230 33 | | | | | | | | | 43 |0-21| 14 47| 3 41 | 1 34| 20 02|Total |851 38 | | | | | | | | | ----+----+-------+--------+-------+-------+-------------+--------| | | | | | | | | 43 |0-18| 11 02| 2 54 | 0 16| 14 12| | | ----+----+-------+--------+-------+-------+-------------+--------| 12 |0-07| 1 20| 2 35 | 0 14| 4 12| | | ----+----+-------+--------+-------+-------+-------------+--------| 12 |0-05| 0 58| 1 44 | 0 10| 2 52| | | ----+----+-------+--------+-------+-------+-------------+--------| | | | | | | | | 12 |0-06| 1 09| 2 05 | 0 12| 3 26| | | ----+----+-------+--------+-------+-------+-------------+--------| 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.

=====+=============================+=============================+ | North Manhattan. | South Manhattan. | +-----------------------------+----------------------+------+ | Number of | Station |Lin. | Number of | Station |Lin. | | rings | of |ft. | rings | of |ft. | | erected. | leading |for | erected. | leading |for | +-----------+ ring. |month.+-----------+ ring. |month.| |For | To | | |For |To | | | Month|month|date | | |month|date | | | -----+-----+-----+----------+------+-----+-----+----------+------+ 1905 | | | | | | | | | May | 26 | 26|200 + 83.7| 63.7 | | | | | June | 26 | 52|201 + 49.0| 65.3 | | | | | July | 28 | 80|202 + 19.2| 70.2 | | | | | Aug | 26 | 106|202 + 84.3| 65.1 | | | | | Sept | 21 | 127|203 + 36.8| 52.5 | 31 | 31|200 + 96.4| 76.4 | Oct | 25 | 152|203 + 99.4| 63.6 | 45 | 76|202 + 09.2|112.8 | Nov | 31 | 183|204 + 76.9| 77.5 | 31 | 107|202 + 86.5| 77.3 | Dec | 59 | 242|206 + 24.6|147.7 | 34 | 141|208 + 71.8| 85.3 | 1906 | | | | | | | | | Jan | 94 | 336|208 + 59.8|235.2 | 27 | 168|304 + 39.4| 67.6 | Feb | 78 | 414|210 + 54.9|195.1 | 64 | 232|205 + 99.6|160.2 | Mar | 56 | 470|211 + 95.2|140.3 | 96 | 328|208 + 39.9|240.3 | April| 119 | 589|214 + 93.0|297.8 | 84 | 412|210 + 59.1|210.2 | May | 129 | 718|218 + 15.7|322.7 | 70 | 482|212 + 25.3|165.2 | June | 218 | 936|232 + 60.9|545.2 | 140 | 622|215 + 75.5|350.2 | July | 155 |1,091|227 + 48.5|387.6 | 82 | 704|217 + 80.7|205.2 | Aug | 145 |1,236|231 + 11.2|362.7 | 134 | 838|221 + 15.8|335.1 | Sept | 89 |1,325|233 + 34.1|222.9 | 168 |1,006|225 + 35.8|420.0 | Oct | | | | | 105 |1,111|227 + 98.6|262.8 | Nov | | | | | 7 |1,118|228 + 16.8| 18.2 | =====+=====+=====+==========+======+=====+=====+==========+======+

=====+=============================+============================+======== | North Weehawken. | South Weehawken. | +-----------------------------+----------------------------+Average | Number of | Station |Lin. | Number of | Station |Lin. |progress | rings | of |ft. | rings | of |ft. |per | erected. | leading |for | erected. | leading |for |shield +-----------+ ring. |month.+-----------+ ring. |month|lin. ft. |For | To | | |For |To | | |per Month|month|date | | |month|date | | |month. -----+-----+-----+----------+------+-----+-----+----------+-----+-------- 1905 | | | | | | | | | May | | | | | | | | | 15.9 June | 24 | 24|260 + 76.6| 59.3 | 12 | 12|260 + 70.0| 30.0| 38.6 July | 12 | 36|260 + 46.6| 30.0 | 15 | 27|260 + 32.4| 37.6| 34.4 Aug | 15 | 51|260 + 09.1| 37.5 | 16 | 43|260 + 07.4| 25.0| 31.9 Sept | 1 | 52|260 + 06.6| 2.5 | 18 | 61|259 + 47.2| 60.2| 47.9 Oct | 10 | 62|259 + 81.5| 25.1 | 20 | 81|258 + 97.2| 50.0| 62.9 Nov | 29 | 91|259 + 09.0| 72.5 | 39 | 120|257 + 99.7| 97.5| 81.2 Dec | 46 | 137|257 + 94.0|115.0 | 77 | 197|256 + 07.1|192.6| 135.1 1906 | | | | | | | | | Jan | 77 | 214|256 + 01.4|192.6 | 73 | 270|254 + 24.6|182.5| 169.4 Feb | 133 | 347|252 + 68.6|332.8 | 165 | 435|250 + 11.7|412.9| 275.2 Mar | 142 | 489|249 + 13.3|355.3 | 111 | 546|247 + 34.0|277.7| 253.4 April| 32 | 521|248 + 33.3| 80.0 | 78 | 624|245 + 38.9|195.1| 195.7 May | 121 | 642|245 + 30.6|302.7 | 2 | 626|245 + 33.9| 5.0| 198.9 June | 162 | 804|241 + 25.3|405.3 | 157 | 788|241 + 41.1|392.8| 423.4 July | 113 | 917|238 + 42.4|282.9 | 118 | 901|238 + 45.9|295.2| 292.7 Aug | 138 |1,055|234 + 97.1|345.3 | 140 |1,041|234 + 95.8|850.1| 348.3 Sept | 55 |1,110|233 + 59.5|137.6 | 177 |1,218|230 + 52.8|443.0| 305.9 Oct | 1 |1,111|233 + 57.0| 2.5 | 94 |1,312|228 + 16.8|236.0| 125.3 Nov | 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 CO_{2} in the air was also measured daily, as the specifications called for not more than 1 part of CO_{2} 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.

Transportation and Disposal.

The transportation and disposal will be described under the following headings:

Receipt and Unloading of Materials, Surface Transportation, Tunnel Transportation, Disposal.

_Receipt and Unloading of Materials._--At the Manhattan Shaft the contractor laid a spur siding into the yard from the freight tracks of the New York Central Railroad, which immediately adjoins the yard on the west. There was also wharfage on the river front about 1,500 ft. away.

At the Weehawken Shaft there were four sidings from the Erie Railroad and one from the West Shore Railroad. Access to the river was gained by a trestle direct from the yard, and Baldwin Avenue adjoined the yard.

All the iron lining arrived by railroad. It was unloaded by derricks, and stacked so that it was convenient for use in the tunnel. The Manhattan derricks were a pair of steel ones with 39-ft. booms, worked by a 30-h.p., 250-volt, electric motor. There was also a stiff-leg derrick with 50-ft. boom, on a platform near the shaft, which was worked by a 40-h.p., 250-volt motor. At Weehawken there were two 45-ft. boom, stiff-leg derricks of 2 tons capacity, one worked by a 42-h.p. Lidgerwood boiler and engine, and the other by a 25-h.p., 250-volt, electric motor. These derricks were set on elevated trestles near the Erie Railroad sidings. There was a 50-ft. stiff-leg derrick with a 70-h.p. Lidgerwood boiler and engine near the cement warehouse on the West Shore Railroad.

The storage area for iron lining was 1,800 sq. ft. at Manhattan and 63,000 sq. ft. at Weehawken; the maximum quantity of lining in storage at any one time was 150 rings at Manhattan and 1,200 rings at Weehawken.

The cement, which was issued and sold by the Company to the contractor, was kept in cement warehouses; that at the New York side was at Eleventh Avenue and 38th Street, or some 1,200 ft. from the shaft, to which it was brought by team; that at Weehawken was adjacent to the shaft, with a 2-ft. gauge track throughout it and directly connected with the shaft elevator.

_Surface Transportation._--In the early days the excavation was handled in scale-boxes of 1 cu. yd. capacity which were hoisted up the shafts by a derrick, but, when the iron period began, two-cage elevators were put in at each shaft. They were worked by a single, friction-drum, Lidgerwood, steam hoisting engine of 40 h.p.

All materials of construction were loaded on cars on the surface at the point where they were stored, and hauled on these to the elevators, sent down the shaft, and taken along the tunnels to the desired point without unloading.

The narrow-gauge railway on the surface and in the tunnel was of 2-ft. gauge with 20-lb. rails. About 70 flat cars and 50 mining cars were used at each shaft. On the surface at Manhattan these were moved by hand, but at Weehawken, where distances were greater, two electric locomotives on the overhead trolley system were used.

_Tunnel Transportation._--The mining cars shown in Fig. 19 were of 1¼ cu. yd. capacity. The short wheel base and unbalanced loading caused a good many upsets, but they were compact, easily handled, and could be dumped from either side or end.

[Illustration: MUCK CAR (AS USED IN RIVER TUNNELS) CAPACITY 5,000 LBS. OR 1¼ CU. YD. FIG. 19.]

The flat cars shown in Fig. 20 were of 3 tons capacity, and could hold two tunnel segments. As the working face was down grade from the shafts, the in-bound cars were run by gravity. For out-bound cars a cable haulage system was used, consisting of double-cylinder, Lidgerwood, single friction-drum, hoisting engines (No. 32) of 6 h.p., with cylinders 5 in. in diameter and 6 in. stroke and drums 10 in. in diameter. These were handily moved from point to point, but, as there was no tail rope, several men had to be used to pull the cable back to the face. After the second air-lock bulkhead walls had been built, a continuous-cable system, worked electrically, was put in each tunnel between the first and second air-locks.

The engine consisted of an electric motor driving a 3-ft. 6-in. drum hoist around which a ¾-in. steel wire cable passed three times. The cable was led around a sheave, down the tunnel on the right side of the in-bound track, and returned on the left side of the out-bound track. It was then carried around a set of sheaves, where a tension of 1,000 lb. was supplied by a suspended weight which acted on a sheave with a sliding axle on the tension carriage. The cable was supported throughout its length on 8-in. pulleys set in the floor at 50-ft. intervals. All the guide sheaves were 36 in. in diameter.

[Illustration: FLAT CAR FOR TUNNEL SEGMENTS CAPACITY 6,000 LBS. FIG. 20.]

Each car was attached to the cable by a grip at its side. This was fastened and unfastened by hand, but was automatically released just before reaching the turn in the cable near each lock. This system could haul without difficulty an unbalanced load of 10 muck cars, spaced 100 ft. apart, up a 2% grade. The cable operated over about 1,000 ft. of tunnel, the motor being placed at the top of the grade. The driving motor was of the semi-armored, 8-pole, series-wound type, rated at 25 h.p., 635 rev. per min., and using direct current at 220 volts. The speed of handling the cars was limited by their having to pass through the air-locks on a single track. As many as 106 cars have been hauled each way in one 8-hour shift.

_Disposal._--At Manhattan the tunnel muck was carried from the elevator over the upper level of the yard trestle and dumped into bins on the 33d Street side, whence it was teamed to the public dump at 30th Street and North River. At Weehawken the rock excavation was removed by the Erie Railroad on flat cars on which it was dumped by the tunnel contractor, but all the silt muck was teamed away to some marshy ground where dumping privileges were obtained.

The typical forces employed on transportation were as follows:

_Receipt and Unloading of Material: Surface Transportation and Disposal._

At Manhattan Shaft, on 10-hour shifts:

2 Engineers on derricks. @ $3.00 per day. 2 Foremen. " 3.25 " " 15 Laborers loading and unloading iron. " 1.75 " " 7 Laborers on disposal. " 1.75 " " 6 Teams. " 7.50 " "

At Weehawken Shaft, on 10-hour shifts:

3 Engineers on derricks and locomotives. @ $3.00 per day. 16 Laborers loading and unloading iron. " 1.75 " " 3 Foremen. " 3.50 " " 11 Laborers on disposal. " 1.75 " " 6 Teams on disposal. " 6.50 " "

Tunnel Transportation (Including Shaft Elevator):

Shaft elevators and to and from the first air-lock on 10-hour shift:

2 Engineers. @ $3.00 per day. 2 Signalmen. " 2.00 " " 1 Foreman. " 3.00 " " 12 Laborers. " 1.75 " "

Between first lock and working face, on 8-hour shifts, the force varied:

From 1 to 3 (average 2) Hoist engineers @ $3.00 per day. From 0 to 2 (average 1) Lockman " 2.75 " " From 1 to 2 (average 2) Trackmen " 3.00 " " From 2 to 7 (average 4) Cablemen (pulling back cable) " 3.00 " "

_Pumping._--The water was taken out of the invert by a 4-in. blow-pipe which was always kept up to a point near the shield and discharged into the sump near the shaft.

When the air pressure was removed and the blow-pipe device, consequently, was unavailable, small Cameron pumps, driven by compressed air, and having a capacity of about 140 gal. per hour, were used, one being set up wherever it was necessary to keep the invert dry; for example, at points where caulking was in progress.

_Lighting._--The tunnels were lighted by electricity, the current being supplied, at a pressure of 250 volts, from the dynamos in the contractor's power-house.

Two 0000 wire cables were used as far as the second air-locks, about 1,650 ft. from the power-house, on each side; and beyond that point, to the junction of the shields (about 1,750 ft.), 00 and 0 wires were used. These cables also carried the current for the cable haulage system. Two rows of 16-c.p. lamps, provided with reflectors, were used in each tunnel; one row was along the side just above the axis, with the lights at about 30-ft. intervals; the other along the crown, with the lamps halfway between the side lamps, also at 30-ft. intervals. At points where work was in progress three groups of 5 lights each were used. The tunnels as a whole were well lighted, and in consequence work of all kinds was much helped.

_Period No. 2._--_Caulking and Grummeting._--_November, 1906, to June, 1907._--After the metal lining had been built completely across the river in both tunnels, the work of making it water-tight was taken up. This consisted in caulking into the joints between the plates a mixture of sal-ammoniac and iron borings which set up into a hard rusty mass, and in taking out each bolt and placing around the shank under the washer at each end a grummet made of yarn soaked in red lead. These grummets were made by the contractor on the works, and consisted of three or four strands of twisted hemp yarn, known as "lath yarn," making up a rope-like cross-section about ¼ in. in diameter. Usually, one of these under each washer was enough, but in wet gravel, or where bolts were obliquely in the bolt-holes, two were used at each end. After pulling the grummets in, all the nuts were pulled up tight by wrenches about 3 ft. long, with two men on one wrench. Bolts were not passed as tight unless the nut resisted the weight of an average man on a 2½-ft. wrench.

Before putting in the caulking mixture, the joints were carefully scraped out with a special tool, cleaned with cotton waste, and washed with a stream of water. The usual mixture for sides and invert was about 2 lb. of sal-ammoniac and 1 lb. of sulphur to 250 lb. of iron filings or borings. In the arch, 4 lb. of sal-ammoniac and 3 lb. of sulphur to 125 lb. of filings was the mixture. A small hand-hammer was used to drive the caulking tool, but, in the sides and invert, air hammers were used with some advantage. The success of work of this kind depends entirely on the thoroughness with which the mixture is hammered in; and the inspection, which was of an exceedingly monotonous nature, called for the greatest care and watchfulness on the part of the Company's forces, especially in the pocket iron, where each bolt had to be removed, the caulking done at the bottom of the pockets put in, the bolts replaced; and the rest of the pockets filled. The results have been satisfactory, as the leakage under normal air and prior to placing the concrete averaged about 0.14 gal. per lin. ft. of tunnel per 24 hours, which is about 0.0035 gal. per lin. ft. of joint per 24 hours. With each linear foot of joint is included the leakage from 1.27 bolts. Afterward, when the concrete lining was in, the leakage was found to be about 0.05 to 0.06 gal. per lin. ft. of tunnel per 24 hours, which compares favorably with the records of other lined tunnels. The typical gang employed on this work was as follows:

_In Pocket Iron:_

1 General foreman @ $5.00 per day. 1 Mixer " 3.00 " " 1 Nipper " 3.00 " " 5 Caulkers " 3.00 " " 10 Grummeters " 3.00 " "

_In Pocketless Iron:_

1 General foreman @ $5.00 per day. 1 Mixer " 3.00 " " 1 Nipper " 3.00 " " 3 Caulkers " 3.00 " " 12 Grummeters " 3.00 " "

The average amount of caulking and grummeting done per shift with such a gang was (with pocketless grooves), 348 lin. ft. of joint and 445 bolts grummeted; and in pocket iron: 126 lin. ft. of joint and 160 bolts grummeted.

The caulking and grummeting work was finished in June, 1907, this completing the second period.

_Period No. 3._--_Experiments, Tests, and Observations._--_April, 1907, to April, 1908._--The third period, that of tests and observations in connection with the question of foundations, is dealt with in another paper. It occupied from April, 1907, to November, 1908. The results of the information then gathered was that it was not thought advisable to go on with the foundations.

_Period No. 4._--_Capping Pile Bores, Sinking Sumps, and Building Cross-Passages._--_April, 1908, to November, 1908._--In order to reduce the leakage from the bore segments to the least possible amount before placing the concrete lining, it was decided to remove the plugs and replace them with flat cover-plates; these have been described before, together with the filling of Bore Segments No. 2 with mortar to reduce the leakage around the distance piece.

During this period the turnbuckles to reinforce the broken plates were put in, and the sump sunk at the lowest point of the tunnel. These sumps have been described in a previous part of this paper; they were put down without trouble. As much as possible of the concrete lining was put in before the lining castings were taken into the tunnel, as the space inside was very restricted. The first lining casting was bolted to the flat flanges of the sump segment, the bolts holding the latter to the adjacent segments were removed, and the whole was forced down with two of the old shield jacks, taking a bearing on the tunnel. The two together exerted a pressure of about 150 tons. The plugs in the bottom of the sump segment were taken out, and pipes were put in, through which the silt squeezed up into the tunnel and relieved the pressure on the sump segment.

If the silt did not flow freely, a water-jet was used. The sump was kept plumb by regulating the jacks. In this way the sump was sunk, adding lining sections one by one, and finally putting on the top segment, which was composed of three pieces.

The time taken to sink one sump was about 4 days, working one 8-hour shift per day, and not counting the time taken to set up the jacks and bracing. The sinking of each section took from 4 to 6 hours. The air pressure was 25 lb. and the hydrostatic head 41 lb. per sq. in. The force was 1 assistant superintendent at $6.00 per day, 1 foreman at $4.50, and 6 laborers at $3.00 per day.

_Cross-Passages._--It was during this period that the five cross-passages previously mentioned were built. In the case of those in the rock, careful excavation was needed so as to avoid breaking the iron lining. Drilling was done from both ends, the holes were closely spaced, and about 2 ft. 6 in. deep, and light charges of powder were used. The heading, 5 by 7 ft. in cross-section, was thus excavated in five lengths, with 24 holes to a length, and about 23 lin. ft. of hole per yard. About 5.3 lb. of powder per cu. yd. was used. The sides, top, and bottom were then drilled at a very sharp angle to the face and the excavation was trimmed to the right size. This widening out took about 7½ ft. of hole per cu. yd., and 0.9 lb. of powder.

In the passages in silt the excavation had to be 12 ft. wide and 13 ft. 8 in. high to give enough room inside the timbers. The plates at one end of the passage were first removed. An air pressure of 17 lb. was carried, which was enough to keep the silt from squeezing in and yet left it soft enough to be chopped with a spade.

A top heading, of full width and 6 ft. 8 in. high, was first taken out, and the roof was sheathed with 2-in. boards held by 10 by 10-in. head trees at 3-ft. centers, with 10 by 10-in. side trees. The lower 7 ft. of bench was then taken out, a tight floor of 6 by 6-in. cross-timber was put in, and also longer side trees, the head trees being temporarily held by two longitudinal 10 by 10-in. stringers blocked in place. The bulk of the space between the side trees was filled with 10 by 10-in. posts and blocking. The plates at the other end of the passage were then taken out from the other tunnel.

After the excavation was out, the outer reinforced concrete lining was built. Rough forms were used, as the interior surfaces of the passages were to be rendered with a water-proofing cement. A few grout pipes were built in, and all voids outside the concrete were grouted. Grouting was also done through the regular grout holes of the metal lining around the openings.

In the case of the most westerly of the cross-passages at Weehawken, which was in badly seamed rock carrying much water, a steel inter-lining, rather smaller than the concrete, was put in. The space between the concrete and the steel was left open, so that water coming through the concrete lining was stopped by the steel plate. This water was led back to the shield chamber in a special drain laid in the bench of the river tunnel and behind the ducts. From the shield chamber the water ran with the rest of the drainage from the Weehawken Land Tunnels to the Weehawken Shaft sump.

[Illustration: TYPICAL CROSS-SECTIONS SHOWING SUCCESSIVE STAGES IN PLACING CONCRETE IN RIVER TUNNELS FIG. 21.]

_Period No. 5._--_Placing the Concrete Lining._--_November, 1908, to June, 1909._--During the fifth period the concrete lining was put in. This lining was placed in stages, as follows: First, the invert; second, the duct bench; third, the arch; fourth, the ducts; and fifth, the face of the bench. This division can be seen by reference to Fig. 21.

All the work was started on the landward ends and carried toward the middle of the river from both sides. Except where the Weehawken force passed the lowest point of the tunnel, which is at Station 241 or nearly 900 ft. to the west of the middle of the river, all the work was down grade.

Before any concrete was placed, the surface of the iron was cleaned with scrapers and wire brushes, and washed with water. Any leaks in the caulking and grummeting (finished by June, 1907, and therefore all more than 12 months old) were repaired. All the grout hole plugs were examined, and the plugs in any leaking ones were taken out, smeared with red lead, and replaced. The leakage in the caulking was due to the fact that the tunnel had been settling slightly during the whole 12 months of pile tests, and, therefore, had opened some of the joints. After the caulking had been repaired and the surface thoroughly cleaned, the flanges were covered with neat cement (put on dry or poured on in the form of thick grout) just before the concrete was placed.

_Invert Concrete._--The form used for the landward type of concrete, that is, the one with a middle drain, consisted of a frame made of a pair of trussed steel rails on each side of the tunnel and connected at intervals with 6 by 6-in. cross-timbers; two "wing forms" were hung from this frame by adjustable arms. These wings formed the curved sides of the invert, the lip, and the form for the middle drain. The whole form was supported on three wheels, two on the rear end running on a rail laid on the finished concrete, and the third in front attached to the frame by a carriage and running on a rail temporarily laid on the iron lining. The form was braced from the iron lining by 6 by 6-in. blocks.

For the soft-ground type of invert, namely, the one without the middle drain, a form of the same general type was used, except that the form for the middle drain was removed. After the form had been in use for some time, "key pieces" (made of strips of wood about 1 ft. 3 in. in length and 3 by 3 in. in cross-section) were nailed circumferentially on the under side of the wings at 2-ft. intervals. This was done because, at the time, it was not known whether ballasted tracks or some form of rigid concrete track construction would be adopted, and, if the latter, it was desirable not to have the surface smooth.

The concrete was received in cars at the rear end of the form and dumped on a temporary platform. It was then loaded into wheel-barrows on the runways, as shown in Fig. 22. The concrete was thrown from the barrows into the invert, where it was spaded and tamped.

In cases where there was steel-rod reinforcement, the concrete was first brought up to the level of the underside of these rods, which came between the wings; the rods were laid in place, and then more concrete was placed over the rods and brought up to the level of the bottom of the wings. Where there was no reinforcement, the concrete was brought up in one lift.

[Illustration: CONCRETE FORM STANDARD IN RIVER TUNNELS FIG. 22.]

After this was finished, the concrete behind the wings was placed, thoroughly spaded and tamped, and, where there were longitudinal reinforcing rods, these were put in at their proper level. Where there were circumferential rods, the 16-ft. rods had already been put in when the lower part of the concrete was placed. As the invert was being finished off, the 8-ft. rods were embedded and tied in position.

The longitudinal rods were held in place at the leading end of each length of arch by the wooden bulkhead, through which holes were drilled in the proper position. At the rear end they were tied to the rods projecting from the previous length. The quantity of water used in mixing the invert concrete needed very nice adjustment; if too wet, the middle would bulge and rise when the weight of the sides came on it; and, if too dry, it would not pack properly between the flanges of the iron lining. The difficulties as to this were often increased by the flow of accumulated leakage water from the tunnel behind on the concrete while it was being put in. To prevent this, a temporary dam of sand bags was always built across the last length of finished invert concrete before beginning a new length. A sump hole, about 4 by 1 ft. and 1 ft. deep, was left every 800 ft. along the tunnel, and a small Cameron pump was put there to pump out the water.

The invert forms were left in place about 12 hours after the pour was finished. The average time taken to fill a length of 30 feet was 7 hours, the form was then left 12 hours, and it took 2 hours to set it up anew. The total time for one length, therefore, was 21 hours, equal to 34 ft. per 24 hours. At one place, a 45-ft. form was used, and this gave an average speed of 45 ft. per 24 hours.

An attempt was made to build the invert concrete without forms (seeing that a rough finish was desired, as previously explained, to form a key for possible sub-track concrete), but it proved a failure.

The typical working force (excluding transport) was as follows:

1 Foreman @ $3.25 per shift. 2 Spaders " 2.00 " " 9 Laborers " 1.75 " "

The average time taken to lay a 30-ft. length of invert was 7 hours; the two spaders remained one hour extra, smoothing off the surface.

For setting the form, the force was:

1 Foreman @ $4.50 per shift. 5 Carpenters " 3.25 " " 6 Carpenters' helpers " 2.25 " "

The average time taken to erect a form was 2 hours, 1 carpenter and 1 helper remaining until the concrete was finished.

_Duct Bench Concrete._--The duct bench (as described previously) is the portion of the concrete on which the ducts are laid. The exact height of the steps was found by trial, so as to bring the top of the ducts into the proper position with regard to the top and the face of the bench.

Both kinds of duct bench forms were of the same general type. A drawing of one of them is shown on Plate XLII. The form consisted of a skeleton framework running on wheels on a track at the level of the temporary transportation tracks. The vertical faces of the steps were formed by boards supported from the uprights by adjustable arms. The horizontal surfaces were formed by leveling off the concrete with a shovel at the top of the vertical boards. Where the sheets of expanded metal used for bonding came at a step, the lower edge of the boards forming the back of the step was placed 1 in. above the one forming the front of it; but, when the expanded metal came in the middle of a step, a slot 1 in. wide was left at that point to accommodate it.

A platform was formed on the top of the framework for the form, and on this a car forming a sort of traveling stage was run. There was ample room to maintain traffic on a single track through the form. A photograph of the form is shown in Fig. 1, Plate XLIII.

The concrete, for the most part, was received at the form in ¾-cu. yd. dumping buckets. The buckets were lifted by the rope from a small hoisting engine. This rope passed over a pulley attached to the crown of the tunnel and dumped into the traveling stage on the top of the form. In this the concrete was moved along to the point where it was to be deposited, and there it was thrown out by shovels into the form below. For a portion of the period, while the duct bench concrete was being laid, it was not necessary to maintain a track for traffic through the form and, during that period, the concrete for the lower step was placed from below the form, the concrete being first dumped on a temporary stage at the lower track level.

Owing to the horizontal faces of the steps being uncovered, there was a tendency for the concrete there to rise when concrete was placed in the steps above. For this part of the work, also, it was necessary to see that the concrete was not mixed too wet, for, when that was the case, the concrete in the upper steps was very apt to flow out at the top of the lower one. At the same time, there was the standing objection to the mixture being too dry, namely, the responsibility of getting a sufficient amount of spading and tamping done. Particulars of the exact quantity of water used are given later in describing "Mixing." Fig. 2, Plate XLIII, illustrates the process of laying.

In the section of the tunnel in which there were circumferential reinforcement rods in the duct bench, the rods were in place before the laying commenced, as they had been placed with the invert concrete. The circumferential reinforcing rods in the arch came down into the upper part of the duct bench concrete; these rods were put in position and tied to the iron lining in the crown at the same time as the duct bench concrete was being finished off. Openings for the manholes were left in the duct bench at the regular stationing.

The average time taken to fill a length of 35 ft. was about 6 hours; the form was then left in position for about 8 hours--usually enough to let the concrete set properly--and then moved ahead; it then took about 3 hours to set it up again ready to continue work. The total time for a length, therefore, was about 17 hours, equal to an average progress of about 49 ft. per day. The average force engaged in duct bench concrete (not including transport) was:

1 Foreman @ $3.25 per day. 2 Spaders " 2.00 " " 9 Laborers " 1.75 " "

_Arch Concrete._--By far the greater part of the arch work was put in with traveling centers before the face of the bench was built, in which case the whole of the arch was built at once. A short length of arch at each end of the tunnel was built after the face of the bench, in which case the haunches or lower 5 ft. were laid first and the upper part of the arch later.

The first traveling centers were used on the New York side, and were 50 ft. long. The laggings were of 4-in. yellow pine, built up in panels 10 ft. long and 16 in. wide for the sides, and solely longitudinal lagging 5 ft. long for the key.

It was pretty certain that the results to be obtained from forms of such a length would not be satisfactory, and this was pointed out to the contractor, who, however, obtained permission to use them on trial. Grout pipes were built in, as it was not likely that the concrete could be packed tightly into the upper part of the lining.

[Illustration: PLATE XLIII. TRANS. AM. SOC. CIV. ENGRS. VOL. LXVIII, No. 1155. HEWETT AND BROWN ON PENNSYLVANIA R. R. TUNNELS: NORTH RIVER TUNNELS. FIG. 1.]

[Illustration: PLATE XLIII. TRANS. AM. SOC. CIV. ENGRS. VOL. LXVIII, No. 1155. HEWETT AND BROWN ON PENNSYLVANIA R. R. TUNNELS: NORTH RIVER TUNNELS. FIG. 2.]

After about 300 lin. ft. of arch had been built with these forms, a test hole was cut out and large voids were found, and, to confirm this, another hole was cut, and similar conditions observed.

The results were so unsatisfactory that orders were given that the use of longitudinal key lagging should be discontinued, and cross or block lagging used instead. These block laggings were 6 in. in length (in the direction of the tunnel) and 2 ft. in width; at the same time, the system of grout pipes was changed. This will be described later under "Grouting." It was soon found that with block lagging a better job could be made of packing the concrete up into the keys, but the time taken to "key up" a 50-ft. length was so great that the rest of the arch had set by the time the key was finished. Despite a lot of practice, this was the case, even in the unreinforced type. When the reinforcing rods were met, the time for keying up became still greater, and therefore the contractor was directed to shorten the forms to 20-ft. lengths. A typical working force for a 50-ft. length was:

1 Foreman @ $3.25 per day. 4 Spaders " 2.00 " " 12 Laborers " 1.75 " "

Details of the 20-ft. forms are shown on Plate XLIV. The lower 4 ft. of lagging was built on swinging arms, which could be loosened to allow the centers to be dropped and moved ahead. The rest of the lagging was built up in panels 10 ft. long and 1 ft. 4 in. high. The ribs rested on a longitudinal timber on each side; these were blocked up from the top step of the duct bench concrete. When the form was set, or when it was released, it was moved ahead on rollers placed under it.

The concrete was received at the form in ¾-cu. yd. dumping buckets; from the flat cars on which they were run, these were hoisted to the level of the lower platform of the arch form. At this level the concrete was dumped on a traveling car or stage, and moved in that to the point on the form where it was to be placed. For the lower part of the arch, the concrete was thrown directly into the form from this traveling stage, but, for the upper part, it was first thrown on the upper platform of the arch. The hoisting was done by a small Lidgerwood compressed-air hoister, and set up on an overhead platform across the tunnel. The pulley over which the cable from the hoister passed was attached to the iron lining near one end of the form, and the traveling stage ran back from the arch form on a trailer, shown on Plate XLIV. When it was impossible to hang a pulley--owing to the concrete arch having been built at the point where the trailer stood--an =A=-frame was built on the trailer, and the pulley was attached to that.

In laying the lower part of the arch, about 1 ft. of lagging (including the swinging arms) was first set, the other panels being pulled up toward the top of the arch. When that was filled, the next panel above was lowered into place, and the work continued. As the concrete rose toward the key, it was packed up to a radial surface, so that the arch would not be unduly weakened if the sides set before the key was placed. All the time, great care was taken to see that the concrete was carefully packed into the segments of the metal lining. The quantity of water used in the concrete was carefully regulated, more being used in the lower than in the upper parts of the arch.

In places where there were no reinforcing rods, the width of the concrete key was the length of the block lagging, namely, 2 ft. Where there was circumferential reinforcement, the key had to be more than 5 ft. wide, in order to take the 5-ft. closure rods used in the key. This naturally increased the time of keying very much. On the places where the 5-ft. longitudinal laggings were used, it was impossible to fill the flanges of the metal lining much higher than their undersides.

As the concrete used in the key had to be much drier than that used elsewhere, it was not easy to get a good surface. This trouble was overcome by putting a thin layer of mortar on the laggings just before the concrete was put in.

The overhead conductor pockets were a great hindrance to the placing of the key concrete, especially where the iron was below true grade. Whenever an especially troublesome one was met, a special grout pipe was put in to fill up unavoidable holes by grouting after the concrete had set. All the circumferential reinforcing rods were bent in the tunnel by bending them around a curved form of less diameter than the required bend. This generally left them all right in the middle of their length, but with their end portions too straight; in such cases the ends were bent again. All rods were compared with a template before being passed for use.

The arch forms were left up for 48 hours after keying was finished. Levels taken after striking the forms showed that no appreciable settlement occurred. An average gang for a 20-ft. length of arch was:

1 Foreman @ $3.25 per shift. 2 Spaders " 2.00 " " 10 Laborers " 1.75 " "

Table 30 shows the progress attained under various conditions.

Whenever the face of the bench concrete was constructed before the arch, the latter was built in two separate portions, that is, the bottom 5 ft., or "haunches" of the arch, as they were termed, were built on each side and the rest of the arch later. This involved the use of two separate sets of forms, namely, for the haunch and for the arch. Not very much arch was built in this way, and, as the methods were in principle precisely the same as those used when all the arch was built in one operation, no detailed description is needed.

No provision was made in the contract for grouting the concrete arch, but it soon became evident that by ordinary methods the top part of the concrete could not be packed solid against the iron segments, especially in the keys. As it was imperative to have the arch perfectly solid, it was determined to fill these unavoidable gaps with a 1:1 Portland cement grout, at the same time making every effort to reduce the spaces to a minimum. This made it necessary to build grout pipes into the concrete as it was put in.

The first type of grout pipe arrangement is shown as Type _A_, in Fig. 23. This was used with the longitudinal key laggings; when this method was found to be no good, and cross-laggings were used, the system shown as Type _B_, in Fig. 23, was adopted, in which vents were provided to let out the air during grouting. The expense of these pipes was high, and the contractor obtained permission to use sheet-iron tubes, which, however, were found to be unsuitable, so that the screwed pipes were used again. The contractor next obtained permission to try dispensing altogether with the vent pipes, and so Type _C_, in Fig. 23 was evolved. This, of course, was found to be worse than any of the other systems, as the imprisoned air made it impossible to force grout in. Several other modifications were made, and are shown in Fig. 23.

It was then decided to devise as perfect a system as possible, without allowing the question of cost to be the ruling factor, and to use that system throughout. In this system, shown as Type _S_, in Fig. 23, most of the vent pipes were contained in the concrete, and their size was independent of the thickness of the arch, so that they were easily fixed in position and not subject to disturbance while placing the concrete. This system was used for about 80% of the total length of the tunnel, and proved entirely satisfactory. The machine used for grouting was the same as that used for grouting outside the metal lining.

TABLE 30.--AVERAGE TIME TAKEN FOR VARIOUS OPERATIONS CONNECTED WITH BUILDING CONCRETE ARCHES IN SUBAQUEOUS TUNNELS.

==========+=============+========+================+=========+=========+ Average |Type of |Length |Time, in hours, |Time, |Time, | time |reinforcement|of |moving and |in hours,|in hours,| in hours, | |section,|erecting forms. |placing |placing | form stood| |in | |concrete |concrete | after | |feet. | |in arch. |in key. | filing. | | | | | | | | | | | | ----------+-------------+--------+----------------+---------+---------+ 70 | { A | } 50 | 20 | 15 | 15.40 | | {day work | } | ______/\______ | | | | | |/ \| | | | { A | } |Moving Erecting| | | | {day work | } 20 | 2 3 | 8.30 | 2.40 | | | | | | | 53 | { B | } | | | | | {day work | } 20 | 2 3 | 10.40 | 11.20 | | | | | | | 58 | { C | } | | | | | {day work | } 20 | 2 3 | 11.00 | 7.20 | | | | | | | 58 | { D | } | | | | | {day work | } 20 | 2 3 | 9.30 | 4.35 | | | | | | | 53 | { D | } | | | | | {day work | } 20 | 2 3 | 6.15 | 2.05 | | | | | | | 53 | {Sub-Type | } 20 | 2 3 | 6.00 | 3.00 | | No. 1 | } | | | | | piece work | } | | | | ==========+=============+========+================+=========+=========+

==========+=========+===========+===========+============ Average |Time, |Total Time |Total time |Remarks. time |in hours,|in hours, |in hours, | in hours, |placing |for moving,|per linear | form stood|concrete |erecting, |foot, | after |in key |and filling|for moving,| filing. |and arch | |erecting, | | | |and filling| ----------+---------+-----------+-----------+------------ 70 | 30.40 | 50.40 | 1.01 | | | | | | | | | | | | | | 11.10 | 16.10 | 0.50 | | | | | 53 | | | |Includes | 22.10 | 27.00 | 1.35 |placing rods | | | | 58 | | | | | 18.20 | 23.20 | 1.16 | do. | | | | 58 | | | | | 14.25 | 19.25 | 0.91 | do. | | | | 53 | | | | | 8.20 | 13.20 | 0.05 | do. | | | | 53 | 9.00 | 14.00 | 0.70 | do. | | | | | | | | ==========+=========+===========+===========+============

[Illustration: FIG. 23.]

The only compressed air available was the high-pressure supply, at about 90 lb.; a reducing valve, to lower this pressure to 30 lb. was used between the air line and the grouting machine. This was thought to be about as high a pressure as the green concrete arch would stand, and, even as it was, at one point a section about 2 ft. by 1 ft. was blown out.

A rough traveling stage resting on the bottom step of the duct bench concrete was used as a working platform. In the earlier stages of the work the grouting was carried on in a rather haphazard manner, but, when the last system of grout and vent pipes was adopted; the work was undertaken systematically, and was carried out as follows:

Two 20-ft. lengths of arch were grouted at one time, and, in order to prevent the grout from flowing along the arch and blocking the pipes in the next lengths, a bulkhead of plaster was made at the end of every second length to confine the grout.

After a section had been grouted, test holes were drilled every 50 ft. along the crown to see that all the voids were filled; if not, holes were drilled in the arch, both for grouting and for vents, and the faulty section was re-grouted. An average of ¾ bbl. of cement and an equal quantity of sand was used per linear foot of tunnel. The average amount put in by one machine per shift was 15 bbl., and therefore the average length of tunnel grouted per machine per shift was 20 ft. The typical working force was:

1 Foreman @ $3.75 per shift 1 Laborer running grout machine " 2.00 " " 2 Laborers handling cement and sand. " 1.75 " " 1 Laborer tending valve and grout pipes " 1.75 " "

After the grouting was finished, the arches were rubbed over with wire brushes to take off discoloration, and rough places at the junctions of adjoining lengths or left by the block laggings were bush-hammered.

_Face of Bench Concrete._--The form used for this portion of the work is shown on Plate XLV. It consisted of a central framework traveling on wheels, and, from the framework, two vertical forms were suspended, one on each side, and equal in height to the whole height of the bench. Adjusting screws were fitted at intervals both at top and bottom, and thus the position of the face forms could be adjusted accurately. The face forms were built very carefully of 3-in. tongued and grooved yellow pine, and one 50-ft. form was used for 3,000 ft. of tunnel without having the face renewed. Great care was taken to set these forms true to line and grade, as the appearance of the tunnel would have been ruined by any irregularity. Joints between successive lengths were finished with a =V=-groove.

The concrete was received at the form in dumping buckets; these were hoisted to the top of the form by a Lidgerwood hoister fixed to a trailer. The concrete was placed in the form by shoveling it from the traveling stage down chutes fitted to its side. The quantity of water to be used in the mixture needed careful regulation. The first few batches in the bottom had to be very wet, and were made with less stone than the upper portion, in order that the concrete would pack solidly around the niche box forms and other awkward corners.

The forms for the ladders and refuge niches were fastened to the face of the bench forms by bolts which could be loosened before the main form was moved ahead, and in this way the ladder and niche forms were left in position for some time after the main form was removed.

At first the forms were kept in place for 36 hours after finishing a length, but, after a little experience, 24 hours was found to be enough. In the summer, when the rise of temperature quickened the set, the time was brought down to 18 hours. The average time taken for a 50-ft. length was:

Laying concrete 4½ hours. Interval for setting 18 " Moving forms ahead and resetting 5 " ------- Total 27½ hours.

The typical working gang was:

_Laying Concrete._

1 Foreman @ $3.25 per shift. 2 Spaders " 2.00 " " 8 Laborers " 1.75 " "

_Moving and Setting Forms._

1 Foreman @ $4.00 per shift. 10 Laborers " 1.75 " "

After the forms were removed, any rough places at the lower edge, where the concrete joins the "lip," were bush-hammered; no other cleaning work was done.

_Duct Laying and Rodding._--The design and location of the ducts have already been described. It will have been seen that the duct-bench concrete was laid in steps, on which the ducts were laid, hence the maintenance of the grade and line in the ducts was an easy matter. The only complication was the expanded metal bonds, which were bent up out of the way of the arch forms and straightened out again after the arch forms had passed. The materials, such as ducts, sand, and cement, were brought into the tunnel by the regular transportation gang. The mortar was mixed in a wooden trough about 10 ft. long, 2 ft. 6 in. wide and 8 in. deep.

After the single-way ducts had been laid, all the joints were plastered with mortar, in order to prevent any foreign substance from entering the ducts. This was not necessary with the multiple duct, as the joints were wrapped with cotton duck. The ducts were laid on a laying mandrel, and, as soon as possible after the concrete was laid around a set of ducts, they were "rodded" with a rodding mandrel. Not many obstructions were met, and these were usually some stray laying mandrel which had been left in by mistake, or collections of mortar where the plastering of the single-way joints had been defective.

In the 657,000 duct ft. of conduit in the river tunnels only eight serious obstructions were met. That the work was of exceptionally high quality is shown by the fact that a heavy 3-in. lead cable has been passed through from manhole to manhole (450 ft.) in 6 min., and the company, engaged to lay the cables in these ducts, broke all its previous records for laying, not only for tunnel work, but also in the open.

Fig. 1, Plate XXXV, shows a collection of the tools and arrangements used in laying and rodding ducts. The typical working force was:

_Laying Multiple Ducts._

1 Foreman @ $3.50 per shift. 9 Laborers " 1.75 " "

_Laying Single-Way Ducts._

1 Foreman @ $3.50 per shift. 8 Laborers " 1.75 " "

_Rodding Multiple Ducts._

1 Foreman @ $3.50 per shift. 5 Laborers " 1.75 " "

_Rodding Single-Way Ducts._

1 Foreman @ $3.50 per shift. 5 Laborers " 1.75 " "

The average progress per 10-hour shift with such gangs was:

Laying multiple ducts 4,000 duct ft. Laying single-way ducts 1,745 " " Rodding multiple ducts 4,040 " " Rodding single-way ducts 2,532 " "

No detailed description need be given of the concreting of the cross-passages, pump chambers, sumps, and other small details, the design of which has been previously shown. The concrete was finished on June 1st, 1909.

_Period No. 6._--_Final Cleaning Up._--_June, 1909, to November, 1909._--As soon as all the concrete was finished, the work of cleaning up the invert was begun. A large quantity of débris littered the tunnels, and it was economical to remove it as quickly as possible. The remaining forms were first removed, and hoisting engines, supported on cross-timber laid across the benches, were set up in the middle of the tunnel at about 500-ft. intervals.

Work was carried on day and night, and about 169 ft. of single tunnel was cleared per 10-hour shift. Work was begun on May 28th, and finished on July 15th, 1909. For part of the time it was carried on at two points in each tunnel, working toward the two shafts, but when the work in the Weehawken Shaft, which was being done at the same time, blocked egress from that point, all material was sent out by the Manhattan Shaft.

The total quantity of material removed was 5,350 cu. yd., or about 0.44 cu. yd. per lin. ft. of tunnel. The average force per shift was:

_In Tunnel._

3 Foremen @ $3.25 per shift 1 Hoist engineer " 3.00 " " 1 Signalman " 2.00 " " 38 Laborers " 1.75 " "

_On the Surface._

1 Foreman @ $3.25 per shift 1 Hoist engineer " 3.00 " " 1 Signalman " 2.00 " " 12 Laborers " 1.75 " "

After the cleaning out had been done, the contractor's main work was finished. However, quite a considerable force was employed, up to November, 1909, in doing various incidental jobs, such as the installation of permanent ventilation conduits and nozzles at the intercepting arch near the Manhattan Shaft, the erection of a head-house over the Manhattan Shaft, and collecting and putting in order all the miscellaneous portable plant, which was either sold or returned to store, sorting all waste materials, such as lumber, piping, and scraps of all kinds, and, in general, restoring the sites of the working yards to their original condition.

Concrete Mixing.

The plant used in mixing the concrete for the land tunnels was pulled down and re-erected before the concrete work in the river tunnels was begun. At the New York shaft two new bins for sand and stone were built, bringing the total capacity up to 950 cu. yd. Two No. 6 Ransome mixers, driven electrically by 30-h.p. General Electric motors, using current from the contractor's generators, were set up on a special platform in the intercepting arch.

At Manhattan the sand and stone were received from the bins in chutes at a small hopper built on the permanent upper platform of the intercepting arch. Bottom-dumping cars, divided by a partition into two portions, arranged to hold the proper quantities of sand and stone for a 4-bag batch of concrete, were run on a track on this upper platform, filled with the proper quantities of sand and stone, and then run back and dumped into the hoppers of the mixer. After mixing, the batch was run down chutes into the tunnel cars standing on the track below. The water was brought in pipes from the public supply. It was measured in barrels by a graduated scale within the barrels. The water was not put into the mixer until the sand and stone had all run out of the mixer hopper. The mixture was revolved for about 1½ min., or about 20 complete revolutions.

At Weehawken Shaft the mixing plant was entirely rebuilt. Four large bins, two for sand and two for stone, were built in the shaft. Together, they held 430 cu. yd. of stone and 400 cu. yd. of sand. The sand and stone were dumped directly into the bins from the cars on the trestle which ran from the wharf to the shaft. The materials were run through chutes directly from the bins to the hoppers of the mixers, where they were measured. Two No. 6 Ransome mixers, electrically driven, were used here, as at New York, and, as there, the water was led into measuring tanks before being let into the mixer.

The quantity of water used in the various parts of the concrete cross-section, for a 4-bag batch consisting of 1 bbl. (380 lb.) of cement, 8.75 cu. ft. of sand, and 17.5 cu. ft. of stone, is given in Table 31.

TABLE 31.--QUANTITY OF WATER PER 4-BAG BATCH OF CONCRETE, IN U.S. GALLONS.

==========================+==========+==========+========== Portion of cross-section. | Maximum. | Minimum. | Average. --------------------------+----------+----------+---------- Invert | 40 | 20 | 26 Duct bench | 36 | 21 | 27 Arch (excluding key) | 37 | 19 | 25 Key of arch | 27 | 15 | 20 Face of bench | 31 | 22 | 27 ==========================+==========+==========+==========

The maximum quantities were used when the stone was dry and contained more than the usual proportion of fine material, the minimum quantity when the sand was wet after rain.

The resulting volumes of one batch, for various kinds of stone, are given in Table 32.

TABLE 32.--VOLUME OF CONCRETE PER BATCH, WITH VARIOUS KINDS OF STONE.

========+===========+================+===========+==================| | | Resulting | | | DESCRIPTION OF STONE. |volume per | | Mixture.|-----------+----------------| barrel of | Remarks. | | | |cement, in | | | Passed | Retained on | cubic | | | screen. | screen. | yards. | | --------+-----------+----------------+-----------+------------------| 1:2½:5 | 1½-in. | 3/8-in. | 0.815 | Measured in air | 1:2½:5 | 2½-in. |Run of crusher. | 0.827 | " " " | 1:2½:5 | -- |General average.| 0.808[D]|Measured from plan| 1:2½:5 | 2-in. | 1½-in. | 0.768[E]| " " " | ========+===========+================+===========+==================|

[D] Average for whole of River Tunnel section.

[E] Average from 7,400 cu. yd. in Land Tunnel section.

The sand used was practically the same for the whole of the river tunnel section, and was supposed to be equal to "Cow Bay" sand. The result of the mechanical analysis of the sand is shown on Plate XLVI. The stone was all trap rock. For the early part of the work it consisted of stone which would pass a 2-in. ring and be retained on a 1½-in. ring, in fact, the same as used for the land tunnels. This was found to be too coarse, and for a time it was mixed with an equal quantity of fine gravel or fine crushed stone. As soon as it could be arranged, run-of-crusher stone was used, everything larger than 2½ in. being excluded. About three-quarters of the river tunnel concrete was put in with run-of-crusher stone. The force was:

_At Manhattan._

1 Foreman @ $3.00 per shift 4 Men on sand and stone cars " 1.75 " " 4 Men handling cement " 1.75 " " 2 Men dumping mixers " 1.75 " "

_At Weehawken._

1 Foreman @ $3.00 per shift 2 Men hauling cement " 1.75 " " 2 Men dumping mixers " 1.75 " "

The average quantity of concrete mixed per 10-hour shift was about 117 batches, or about 90 cu. yd. The maximum output of one of the mixers was about 168 batches, or 129 cu. yd. per 10-hour shift.

Transportation.

_Surface Transportation._--At Manhattan the stone and sand were received in scows at the wharf on the river front. For the first part of the work, the wharf at 32d Street and North River was used, and while that was in use the material was unloaded from the scows into scale-boxes by a grab-bucket running on an overhead cable, and then teamed to the shaft. For the latter part of the work, the wharf used was at 38th Street and North River, where facilities for unloading were given to the contractor by the Pennsylvania Railroad Company which was the permanent lessee of the piers. The material was unloaded into scale-boxes by a grab-bucket operated by a derrick, and teamed to the shaft. When the scale-boxes arrived at the shaft they were lifted from the trucks by derricks and dumped into the bins.

At Weehawken all the stone and sand, with the exception of the stone crushed on the work, was received by water at the North slip. Here it was unloaded by a 2-cu. yd. grab-bucket and dumped into 3-cu. yd. side-tipping cars, which were hauled by a small steam locomotive over the trestle to the shaft, where they were dumped directly into the bins.

Before beginning the concrete lining, the 2-ft. gauge railway, which had been used for the surface transportation during the driving of the iron-lined tunnels, was taken up and replaced by a 3-ft. gauge track consisting largely of 30-lb. rails. The cars were 3-cu. yd. side-dumping, with automatic swinging sides. Two steam locomotives which were being stored at Weehawken (part of the plant from another contract), were used for hauling the cars in place of the electric ones used with the 2-ft. gauge railway.

_Tunnel Transport._--The track used in the tunnel was of 2-ft. gauge, laid with the 20-lb. rails previously used in driving the iron-lined tunnels. The mining cars (previously mentioned in describing the driving of the iron-lined tunnels) were used for transporting the invert concrete, although, for most of the work, dumping buckets carried on flat cars were used. Several haulage systems were considered for this work, but not one of them was thought to be flexible enough to be used with the constantly changing conditions, and it was eventually decided to move all the cars by hand, because, practically all the work being down grade, the full cars could be run down by gravity and the empty ones pushed back by hand. Two men were allotted to each car, and were able to keep the traffic moving in a manner that would have been perhaps impossible with any system of mechanical haulage. This system was apparently justified by the results, for the whole cost of the tunnel transport, over an average haul of about 2,000 ft., was only about 50 cents per cu. yd., which will be found to compare favorably with mechanical haulage on similar work elsewhere, provided full allowance is made for the use of the plant and power.

_Force Employed._--The average force employed on transport, both on the surface and in the tunnel, is shown in Table 33.

Costs.

During the work, careful records of the actual cost to the contractor of carrying out this work were kept by the Company's forces; these costs include all direct charges, such as labor and materials, and all indirect charges such as head office, plant depreciation, insurance, etc., but do not include the cost of any financing, of which the Company had no information.

TABLE 33.--AVERAGE FORCE PER SHIFT FOR TRANSPORTATION IN TWO TUNNELS.

========+==================+=====+==========+============+===========+ Location|Grade |Rate | WORK IN PROGRESS | | | |----------+------------+-----------+ | | | Two |Two arches, |Four arches| | | | inverts |two inverts,| and one | | | | and two |and two duct| face of | | | | duct | benches | bench | | | | benches | | | --------+------------------+-----+----------+------------+-----------+ {|Foreman |$3.00| 2 | 2 | 2 | Tunnel {|Laborer | 1.75| 24 | 28 | 70 | {|Switchmen | 2.00| | 2 | 2 | {|Hoisting engineers| 3.00| 2 | 4 | 5 | {|Foreman | 3.00| 1 | 1 | 2 | Surface{|Laborers | 1.75| 8 | 8 | 15 | {|Teams | 6.50| 1 | 1 | 2 | ========+==================+=====+==========+============+===========+

Field Engineering Staff.

The field staff may be considered as divisible into five main divisions:

(_A_).--Construction, including alignment,

(_B_).--Cost records,

(_C_).--Testing of cement and other materials of construction,

(_D_).--Photography,

(_E_).--Despatch-boat service.

(_A_).--_Construction_ (_Inspection and Alignment_) _Staff._--A comparatively large staff was maintained by the Company, and to this two causes contributed. In the first place, the contractor maintained no field engineering staff, because, early in the proceedings, it was arranged that the Company would carry out all this work, and thus avoid the overlapping, confusion, and lack of definite responsibility which often ensues when two engineering forces are working over the same ground. Even had the contractor maintained an engineering force, it would have been necessary for the Company to check most of the contractor's work.

In the second place, this work gave rise to a number of special surveys, tests, borings, and observations of various kinds, most of which were kept up as a part of the regular routine work, and this necessitated a staff. Also, for a whole year, active progressive work was at a standstill while the pile tests were going on.

(_B_).--_Cost Records Staff._--A distinct feature was made of keeping as accurately as possible detailed records of the actual cost to the contractor of carrying out the work. A small staff of clerks, retained solely for this purpose, tabulated and recorded the information furnished by the members of the construction staff. About $12,000, altogether, was spent in salaries in this department, and it may be considered an extremely wise investment, for, not only is the information thus obtained of great value and interest in itself, but it also puts the Company in an excellent position should any claim or discussion arise with the contractor.

(_C_).--_Cement-Testing Department._--As the Company furnished the cement to the contractor, it became incumbent to make careful tests of the quality. A cement-testing laboratory was established at the Manhattan Shaft offices, under the charge of a cement inspector who was furnished with assistants for sampling, shipping, and testing cement. All materials used on the work, such as bricks, sand, stone, water-proofing, etc., were tested here, with the exception of metals, which were under the charge of a metal inspector reporting directly to the head office. This department cost about $10,000 for salaries and $3,000 for apparatus and supplies, or about $13,000, in all.

There were 800,000 bbl. of cement tested, and samples from 2,100,000 brick. A large amount of useful information has resulted from the work of this laboratory.

(_D_).--_Photography._--It was desired to keep a complete photographic record of the progress of the work, and therefore a photographer was appointed, with office room at the Manhattan Shaft. The photographer took all the progress photographs on the work of the North River Division, made photographic reductions of all drawings and plans, made lantern slides of all negatives of a more important nature, and, in addition, during the period of compressed air, analyzed the samples of compressed air, brought into the office for the purpose, for the amount of CO_{2} present. About $8,000 was spent on this department.

(_E_).--_Despatch-Boat Service._--To provide access to the New Jersey side, a despatch boat was purchased. This boat was at first (June, 1904) chartered, and in May, 1905, was bought outright, and ran on regular schedules, day and night. It continued in the service until April, 1909, when it was given up, as the tunnels were so far completed that they provided easy access to New Jersey. The cost of the boat (second-hand) was about $3,000. It was then thoroughly overhauled and the cabin remodeled. The monthly cost, when working a 12-hour shift, was $270 for manning, $65 for supplies, and $64 for coal. On two 12-hour shifts, the monthly cost was $533 for manning, $100 for supplies, and $96 for coal. About 100,000 passengers were carried during the boat's period of service, and the total cost was about $37,500.

For the major part of the period embraced by this paper, B. H. M. Hewett, M. Am. Soc. C. E., served as General Resident Engineer, in charge of the Field Work as a whole.

W. L. Brown, M. Am. Soc. C. E., was at first Resident Engineer of the work constructed from the Manhattan Shaft, while H. F. D. Burke, M. Am. Soc. C. E., was Resident Engineer of the work constructed from the Weehawken Shaft. After the meeting of the shields, Mr. Burke left to take up another appointment, and from that time Mr. Brown acted as Resident Engineer.

It may be said, without reflecting in any way on the manufacturers, that the high standard of all the metal materials also testified to the efficient inspection conducted under the direction of Mr. J. C. Naegeley.

It is impossible to close this brief account of these tunnels without recording the invaluable services at all times rendered by the members of the Company's field staff. Where all worked with one common aim it might seem invidious to single out names, but special credit is due to the following Assistant Engineers: Messrs. H. E. Boardman, Assoc. M. Am. Soc. C. E., W. H. Lyon, H. U. Hitchcock, E. R. Peckens, H. J. Wild, Assoc. M. Am. Soc. C. E., J. F. Sullivan, Assoc. M. Am. Soc. C. E., and R. T. Robinson, Assoc. M. Am. Soc. C. E. Mr. C. E. Price was in charge of the cement tests throughout the entire period, and brought to his work not only ability but enthusiasm. Mr. H. D. Bastow was in charge of the photographic work, and Mr. A. L. Heyer of the cost account records, in which he was ably seconded by Mr. A. P. Gehling, who, after Mr. Heyer's departure, finished the records and brought them into their final shape. The organization of the Company's field engineering staff is shown graphically by Fig. 24.

FIELD ORGANIZATION OF THE O'ROURKE ENGINEERING CONSTRUCTION COMPANY FOR THE BUILDING OF THE PENNSYLVANIA RAILROAD TUNNELS INTO NEW YORK CITY--NORTH RIVER DIVISION. SECTIONS GY EAST, GY WEST SUPPLEMENTARY, GY WEST, AND CO.

GENERAL SUPERINTENDENT. | +------------------------+-------+--+ | | | (General, Surface and Office) (Excavation | ---------------+------------- of Land | | Tunnels) | ASSISTANT GENERAL SUPERINTENDENT | | | GENERAL | | ROCK SUPT | +------------+------------+ | | | | | Tunnel | FIELD SURFACE DESPATCH Supts | OFFICE BOAT Tunnel | Foreman | Civil Head Captain Foremen | Engineer Carpenter Engineer Timbermen | Inspectors Foreman Deck Hands Timbermen | Bookkeepers Carpenter Timbermen's | Paymaster Carpenters Helpers | Head Carpenters' Foremen | Storekeeper Helpers Drillers | Storekeepers Blacksmiths Drillers | Timekeepers Blacksmiths' Foremen | Telephone Helpers Muckers | Operators Foreman Pipe Fitters | Office Boys Laborers Pipe Fitters' | Messengers Laborers Helpers | Janitors Disposal Electricians | Trimmers Hoist | Teamsters Engineers | Signalmen | Muckers | Nippers | Water Boys | | | -------------+--------+-------------------------+--------+----------+ | | | | (Shield Tunnel Driving) (Masonry (Power (Medical | Lining-Rock Plant) Supervision) GENERAL TUNNEL SUPERINTENDENT and River | | | Tunnels) MASTER CHIEF MED ASSISTANT SUPERINTENDENTS | MECHANIC OFFICER | | | | | | | +--------+------------+---------+ | Foreman | EXCAVATION | | GENERAL | Electrician | | IRON LINING CAULKING AND | | Electricians | General | GRUMMETING | | Engineers | Foremen Foremen | Pipefitters | Foreman Resident Foremen Erector Foremen Pipefitters' | Machinist Doctor Drillers Runners Caulkers Helpers | Machinists Drillers Ironmen Grummeters Electricians | Machinists' Powdermen Boltmen Electricians'| Helpers Foremen Helpers | Firemen Timbermen Trackmen | Oilers Timbermen Lockmen | Pumpmen Foremen Transport | Hoist Engineers Muckers Foreman | Signalmen Muckers Transport | Shieldmen Laborers | Laborers Watchmen | Nippers | Water Boys | GENERAL CONCRETE SUPERINTENDENT | TUNNEL SUPERINTENDENTS | +-----------+------------+----------------++-----------+ | | | | | CONCRETE BRICKWORK DUCTS WATER-PROOFING GENERAL

Foremen Foremen Foremen Foremen Pipefitters Carpenters Bricklayers Duct-layers Waterproofers Pipefitters' Carpenters' Bricklayers' Helpers Helpers Laborers Electricians Mixer Carpenters Electricians' Foremen Carpenters' Helpers Mixer Helpers Transport Laborers Foremen Concrete Transport Laborers Laborers Watchmen

FIG. 24.

_Contractor's Organization._--The contracting firm which did the work described in this paper was the O'Rourke Engineering Construction Company, of New York City. The President of this Company was John F. O'Rourke, M. Am. Soc. C. E., the Vice-President was F. J. Gubelman, Assoc. M. Am. Soc. C. E. The General Superintendent was Mr. George B. Fry, assisted by J. F. Sullivan, Assoc. M. Am. Soc. C. E. The duties of General Tunnel Superintendent fell to Mr. Patrick Fitzgerald. The generally pleasant relations existing between the Company and the contractor's forces did much to facilitate its execution.

The organization of the Contractor's field staff is shown on Fig. 25.

PENNSYLVANIA TUNNEL AND TERMINAL RAILROAD COMPANY. NORTH RIVER DIVISION.

SECTIONS GY EAST, GY WEST SUPPLEMENTARY, GY WEST, GJ, AND I, _I. E._, FROM 10TH AVENUE, MANHATTAN, TO THE WEEHAWKEN SHAFT, FIELD ENGINEERING STAFF ORGANIZATION.

GENERAL RESIDENT ENGINEER | +-----------------+------------+------------+---------+----+ | | | | | | (Material Testing) (Photography) | (Cost Records) |(Office) Cement Inspector Photographer | Recording Clerk | Clerks Asst Cement | Asst Recording |Messengers Inspectors | Clerks | (Construction) | | (Despatch Boat) +----------------+ Captain | Engineers RESIDENT ENGINEERS Deckhands (Two during driving of Shield-driven Messengers Tunnels, and one subsequently.) | +---------------------+---+------------------+ | | | (Inspection) (Alignment) (Office) Assistant Engineers Assistant Engineers Draftsmen Chief Tunnel Chiefs of Parties Field Office Inspector Instrumentmen Clerks Tunnel Inspectors Rodmen Cement Surface Inspectors Chainmen Warehousemen Clerks Laborers Janitors

FIG. 25

In conclusion, the writers cannot forego the pleasure of expressing their deep obligation to Samuel Rea, M. Am. Soc. C. E., as representing the Management of the Company, to the Chief Engineer, Charles M. Jacobs, M. Am. Soc. C. E., and to James Forgie, M. Am. Soc. C. E., Chief Assistant Engineer, for their permission to write this paper, and also to all the members of the field office staff for their great and unfailing assistance in its preparation.