Land Tunnels. General.

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The following is a brief account of the main features of the "Land Tunnel" work, by which is meant all the part of the structure built without using tunneling shields.

The Land Tunnels consist of about 977 ft. of double tunnel on the New York side and 230 ft. on the New Jersey side, or a total of 1,207 lin. ft. of double tunnel.

The general design of the cross-section consists of a semi-circular arch, vertical side-walls and a flat invert. The tunnel is adapted for two lines of track, each being contained in its compartment or tunnel. The span of the arch is wider than is absolutely necessary to take the rolling stock, and the extra space is utilized by the provision of a sidewalk or "bench" forming by its upper surface a gangway, out of the way of traffic, for persons walking in the tunnels, and embedded in its mass are a number of vitrified earthenware ducts, for high-and low-tension electric cables. The provision of this bench enables its vertical wall to be brought much nearer to the side of the rolling stock than is usually possible, thus minimizing the effects of a derailment or other accident. Refuge niches for trackmen, and ladders to the top of the bench are provided at frequent intervals. In cases where a narrow street limits the width of the structure, as on the New York side, the two tunnels are separated by a medial wall of masonry, thus involving excavation over the entire width of both tunnels, and in such case the tunnels are spoken of as "Twin Tunnels"; where the exigencies of width are not so severe, the two tunnels are entirely distinct, and are separated by a wall of rock. This type is found on the Weehawken side. The arches are of brick, the remainder of the tunnel lining being of concrete.

New York Land Tunnels.

The work on the Land Tunnels on the Manhattan side was carried on from the shaft at 11th Avenue and 32d Street.

The plans and designs for these tunnels are shown on Plate XXXII. In this short length of about 977 ft. there are no less than nine different kinds of cross-section. The reason for these changes is the fact that the two lines of track are here not straight and parallel to the center line between the tunnels, but are curved, although symmetrical about this center line. The various changes of section are to enable the tunnels to be built in straight lengths, thus avoiding the disadvantages attending the use of curved forms, and at the same time minimizing the quantity of excavation, an item which accounts for from 60 to 70% of the total cost of tunnels of this type. Of course, there are corresponding and obvious disadvantages in the adoption of many short lengths of different cross-sections, and these disadvantages were well brought out in the course of the work; on the whole, however, they may be said to have justified their adoption. These New York Land Tunnels were divided into three contracts, viz.: From Station 190+15 (the Portal to the open work of the Terminal Station at the east side of Tenth Avenue, New York City) to Station 197+60, called "Section Gy-East." The next contract, called "Section Gy-West Supplementary," extended from Station 197+60 to Station 199+20, which is the east side of Eleventh Avenue. The third contract was called "Section Gy-West," and extended from Station 199+20 to Station 231+78 (the dividing line between the States of New York and New Jersey). Thus, for nearly all its length, this contract consists of shield-driven tunnel. The portion between Stations 199+20 and 199+91.5, however, was of the Land Tunnel type, and therefore will be included here. A fourth contract extended from Station 231+78 to the Weehawken Shaft at Station 263+50, and of this all but 230 ft. was of the shield-driven type, only the portion next to the Weehawken Shaft being of the Land Tunnel type.

The four contracts were let to one contractor (The O'Rourke Engineering Construction Company), and the work was carried on simultaneously in all four, so that the division into contracts had no bearing on the methods of work adopted, and these will now be described as a whole and with no further reference to the different sections.

Excavation.

Work was started on the New York side on April 18th, 1904, the Weehawken shaft being at that date still under construction. As will have been noted in the description of the shafts, the contractor found a shaft already prepared for his use, and cross-drifts at grade and at right angles to the future tunnels, and extending across their entire width. The first essential was to get access to the shield chambers, which were to lie about 330 ft. to the west of the shaft, so that the construction of these enlargements in which the shields for the subaqueous tunnels were to be built might be finished as soon as possible and thus allow the earliest possible start to be made with the shield-driven tunnels.

PLATE XXXII.
TRANS. AM. SOC. CIV. ENGRS.
VOL. LXVIII, No. 1155.
HEWETT AND BROWN ON
PENNSYLVANIA R. R. TUNNELS: NORTH RIVER TUNNELS.
Shield Chambers, etc. Typical Sections
Thirty-Second Street Tunnels
Shield Chambers, etc.
Click to view larger image.

With this in view, two bottom headings, on the center line of each of the two tracks, were driven westward from the western cross-heading at the foot of the shaft. When about 138 ft. had been made in this way, the two headings were brought together and a break-up was made to the crown level of the tunnel, as the depth of rock cover was doubtful. From this break-up a top heading was driven westward to Station 200+30. While widening the heading out at Station 200+20 the rock was penetrated on the south side. The exposed wet sand and gravel started to run, and, as a consequence, a change in design was made, the shield chambers (and consequently the start of the shield-driven tunnels) being moved eastward from their original location 133 ft. to their present location. A certain amount of time was necessarily spent in making these changes of design, which involved a rearrangement of the whole layout from the Terminal Station to the start of the River Tunnels. On July 5th, 1904, however, the new design was formally approved. No sooner had this been decided than a strike arose on the work, and this was not settled until August 1st, 1904, but from that time the work progressed without delay. No further reference will be made to the work in the shield chambers, as that will come under the heading of "River Tunnels," being of the segmental, cast-iron lined type.

A top heading was now driven over the original bottom heading west of the shaft, and at the same time the original cross-drifts from the shaft were amalgamated with and broken down by a heading driven at the crown level of the "Intercepting Arch" which here cuts across the ordinary run of tunnel at right angles and affords access to the tunnels from the shafts.

The excavation of the upper portion of the intercepting arch at its southern end gave some trouble, and caused some anxiety, as the rock cover was penetrated and the wet sand and gravel were exposed. This made it necessary to timber all this section heavily, and the tracks of the New York Central Railroad directly above were successfully supported. The general way in which this timbering was carried out will be described under the head of "Timbering."

Meanwhile, the excavation of the tunnels west of the intercepting arch was continued until the North and South Tunnels were taken out to their full outlines, leaving a core of rock between them. This core was gradually removed, and timbering supporting the rock above the middle wall was put in as excavation went on. The ground, which was entirely of micaceous schist, typical of this part of Manhattan, seamed with veins of granite, was rather heavy at the west end, or adjacent to the shield chambers, and required complete segmental timbering across the whole span. One heavy fall of rock in the corewall between the North and South Tunnels took place on November 2d, but fortunately did not extend beyond the limits of the permanent work. On November 7th, 1904, the excavation east of the intercepting arch was begun by driving a bottom heading in the South Tunnel. This was continued to Station 197+14 and then was taken up to the crown level and worked as a top heading with the view of keeping track, by making exploratory borings upward from the roof at frequent intervals, of the rock surface, which was here irregular and not known with any degree of certainty. The work was not pressed with any vigor, because all efforts were then being bent toward excavating from the River Tunnels as much rock as possible. In Section Gy-East the conditions were exceptionally variable, as the rock was subject to sudden changes from a soft crumbling mica schist to broad bands of hard granite, and, in addition, the rock surface was very irregular, and, for a good length of this section, was below the crown of the tunnel, a condition which led to the adoption of the cut-and-cover method for part of the work.

The irregularity in conditions called for varying methods of procedure, but in general the methods were as shown on Plate XXXIII, and described as follows:

In Solid Rock.—Where there was plenty of good rock cover, a top middle heading was driven, which was afterward widened out to the full cross-section of the twin tunnel arches. If necessary, a few lengths of segmental timbering were put in before taking down the bench, which was generally kept some 40 or 50 ft. behind the breast of the heading. After the bench was down, the middle conduit trench was excavated and the trimming done.

In Soft Rock.—Where there was not enough rock cover, or where there was actual soft ground in the roof, wall-plate headings at the springing line level were driven ahead of the remainder of the work. The wall-plates were laid in these, the roof was taken out in short lengths, and segmental timbering spanning from wall-plate to wall-plate was put in. The roof being thus held, the bench excavation proceeded without trouble. Where the rock was penetrated and soft ground showed in the roof, poling boards were driven ahead over the crown-bars, as shown in Fig. 4.

PLATE XXXIII.
TRANS. AM. SOC. CIV. ENGRS.
VOL. LXVIII, No. 1155.
HEWETT AND BROWN ON
PENNSYLVANIA R. R. TUNNELS: NORTH RIVER TUNNELS.
General Method of Excavation Adopted for Land Tunnels General Method of Excavation Adopted for Land Tunnels
Click to view larger image.

Cut-and-Cover Work.—After some 225 ft. had been driven from the intercepting arch, it was found that the crown of the tunnel was continually in soft ground. To ascertain the extent of this condition the contractor decided to make soundings as far as Tenth Avenue, which was done by sinking trial pits and making wash-borings in the street. These soundings showed that there would be soft ground in the crown from Station 194+75 to Station 194+25 (at one point to a depth of 12 ft. below the crown), and on each side of this section the cover was insufficient from Station 193+58 to Station 195+30. This condition being known, it was decided to adopt cut-and-cover work for this length, the principal reasons being that repairs to sewers, streets, and drains would be no more, and probably less, expensive than with the tunnel method; the underpinning of a heavy brick brewery building adjoining the works on the north side would be facilitated, and the opening in the street, through which muck and materials could be handled, would relieve the congested shaft, through which the large volume of muck from the River Tunnels was then being conveyed. On the other hand, the cut-and-cover method was adversely affected by the presence of a heavy timber trestle built down the south side of the street and over which passed all the excavation from the Terminal Station, amounting to a very heavy traffic. As this trestle had to be supported, it complicated the situation considerably. Very little active progress was made between June, 1905, and April, 1906, as the contractor's energies during that time were much taken up with the progress of the shield-driven tunnels. In April, 1906, preparations were made to start a 50-ft. length of open cut, rangers being fixed and sheathing driven; and the sewer which ran down the middle of this street was diverted to the outside of the open-cut length.

April and May were occupied in driving the sheathing down to rock, supporting the trestle, underpinning the adjoining brewery, and excavating the soft material above the rock. On June 2d, 1906, rock was reached, and, by July 31st, the excavation was down to subgrade over nearly the whole 50 ft. in the first length. In the meantime another length was opened up, and eventually a third.

The surface of the rock now seemed to be rising, and the heavy buildings had been passed, so that tunneling was reverted to for the rest of the work, though many difficulties were caused by soft rock in the roof from time to time.

Method of Driving Roof Lagging in Soft Ground. Fig. 4. Method of Driving Roof Lagging in Soft Ground.
Fig. 4.
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When the excavation for the open-cut work of the Terminal Station had advanced to the line of Tenth Avenue, the contractor started a heading from this point and drove westward under Tenth Avenue until the headings driven eastward from the cut-and-cover portion, were met.

This was done to expedite the work under Tenth Avenue, where the ground was not very good, where there were several important gas and water mains in the street, and where, moreover, the tunnels were of exceptionally large span (24 ft. 6 in.), making a total width of some 60 ft. for the excavation. The excavation for the New York Tunnels was practically finished in January, 1908.

Drilling and Blasting.—The foregoing short description will serve to show in a general way the scheme adopted in making the excavation. A few details on drilling and blasting methods may not be out of place.

Percussive drills run by air pressure were used. They were Ingersoll-Sergeant, Nos. 3½, A-86, C-24, and F-24. The air came from the high-pressure compressor previously described. This compressor, without assistance, could supply air for nine drills, but, when fed by compressed air from the lower pressure, its capacity was increased three or four times.

The air was compressed to 100 lb. per sq. in. in the power-house, and was delivered at about 80 lb. per sq. in. at the drills. A 3-in. air line was used. The drill steel was 1?-to 1?-in. octagonal. The holes were about 3¼ in. in diameter at starting and 2? in. at the full depth of 10 ft. The powder used on the New York side was 40% Forcite, the near presence of heavy buildings and lack of much rock cover necessitating light charges and many holes spaced close together.

To compensate the contractor for the inevitable excavation done outside the neat lines of the masonry lining, the excavation was paid for to the "Standard Section Line" which was 12 in. outside the neat lines on top and sides and 6 in. outside at the bottom of the cross-section. The actual amount of excavation done was about 11% greater than that paid for. The distance excavated beyond the neat line, because of the very heavy timbering necessary, was about 2.1 ft. instead of the 1 ft. allowed, and at the bottom about 0.85 ft. instead of the 0.50 ft. paid for.

For a period of 5 months detailed records were kept of the drilling and blasting. About 12,900 cu. yd. of excavation are included. A sketch and table showing the method of driving the heading, the number and location of the holes drilled, and the amount of powder used, is given in Fig. 5. From this and similar figures the information in Table 5 is derived.

TABLE 5.

Portion of excavation. Feet of Hole drilled per cubic Yard of Execavation Pounds of Power Used per Cubic Yard of Excavation
15-ft. 4-in. span-- twin tunnel 19-ft. 6-in. span-- twin tunnel 24-ft. 6-in. span-- twin tunnel 15-ft. 4-in. 19-ft. 6-in. 24-ft. 6-in.
Wall-plate heading [C] 13.00 10.97 10.97 3.77 2.85 2.85
Total heading[C] 7.87 8.17 7.81 2.31 2.02 1.78
Bench and raker bench[C] 5.97 6.15 7.56 0.94 0.93 1.13
Trench[C] 9.82 15.96 18.10 1.84 2.49 2.73
Average for section[C] 6.69 7.43 8.95 1.28 1.30 1.45
Actual amount [D] 6.82 7.27 8.95 1.22 1.24 1.27

[C] Figures taken from typical cross-sections.

[D] This gives the actual amount of drilling done and powder used per cubic yard for the whole period of 5 months of observation, but as this length included 280 ft. of heading and only 220 ft. of bench, the average figures (for powder especially) are too low.

Table 6 gives the rate and cost of drilling, and the cost of powder. It will be seen that the average rate of drilling was 2.71 ft. per hour per drill or 27.1 ft. per drill per shift.

Table 7 shows the result of observation as to the time taken in various subdivisions of the drilling operations. These observations were not carried on for a long enough period to give correct results, but the percentages of time spent on each division of the operation are believed to be about right. The headings of this table are self-explanatory. The necessary delays include all time spent in changing bits, making air-line connections, etc. The unnecessary delays are stoppages caused by lack of supplies or insufficient air pressure.

By Table 6 it will be noticed that the cost of labor for drilling and sharpening steels was about $0.29 per lin. ft. of hole drilled. The total cost, including repairs, supply of air, etc., came to about $0.38, as will be seen from Table 8.

Timbering.—On the New York side nearly the whole length of the excavation needed timbering, to a greater or less extent, and for the most part required timbering of quite a heavy type.

TABLE 6.—Rock Tunnel Excavation under 32d Street, East of Cut-and-Cover Section. Drilling and Blasting.—Detailed Cost of Labor in Drilling, also Quantity and Cost of Powder Used.

Drilling and Blasting. Powder Used.
Type. Date. Total feet drilled. No. of drill shifts (10-hour.) Feet drilled per man per hour. Quantity of excavation, in cubic yards. Cost of labor only. Drilling and sharpening. Total Quantity. Cost per cubic Yard at 11 cents per pound.
Total. Per linear feet. Per cubic yard
Actual. Paid for. Actual. Paid for
1907 Heading Bench Total Heading Bench Total Heading Bench Total Actual. [E] Paid for [F] Pounds.
$ $ $ $ $ $
Ke. May 2,971 5,578 8,549 98 204 302 3.031 2.734 2.831 1,736 1,664 2,331 0.27 1.34 1.40 1,595 0.10 0.10
June 2,093 6,194 8,287 85 223 308 2.462 2.777 2.691 809 698 2,440 0.29 3.01 3.49 1,960 0.27 0.31
July 7,627 7,627 268 268 2.845 2.845 1,022 960 2,031 0.26 1.98 2.11 966 0.10 0.11
Aug. 2,552 2,552 95 95 2.688 2.688 743 716 640 0.25 0.86 0.89 430 0.06 0.07
Sept. 2,133 2,133 79 79 2.700 2.700 238 238 533 0.25 2.24 2.24 280 0.13 0.13
Total 5,064 24,084 29,148 183 869 1,052 2.767 2.770 2.770 4,548 4,276 7,975 0.27 1.75 1.87 5,231 0.13 0.13
Ki. May 6,976 6,976 216 216 3.229 3.229 614 527 1,604 0.23 2.61 3.04 1,230 0.22 0.26
June 4,089 4,089 135 135 3.029 3.029 357 259 1,234 0.30 3.45 4.76 1,036 0.32 0.44
July 3,733 3,733 140 140 2.666 2.666 530 404 1,084 0.29 2.04 2.68 550 0.11 0.15
Aug. 6,715 6,715 249 249 2.769 2.769 925 890 1,901 0.28 2.05 2.13 905 0.10 0.11
Estim 14,742 14,742 46 546 2.700 2.700 3,254 2,908 4,570 0.31 1.40 1.57 2,470 0.08 0.09
Total 11,065 25,190 36,255 351 935 1,286 3.152 2.694 2.819 5,680 4,988 10,393 0.29 1.83 2.08 6,191 0.12 0.14
Ko. May 1,617 1,617 55 55 2.921 2.921 250 188 471 0.29 1.88 2.50 376 0.17 0.22
June 2,948 2,948 107 107 2.755 2.755 496 347 883 0.29 1.78 2.54 357 0.08 0.11
July 3,734 3,734 131 131 2.850 2.850 626 606 1,003 0.27 1.60 1.65 609 0.11 0.11
Aug. 8,260 8,260 290 290 2.848 2.848 709 2,161 0.26 3.00 3.04 918 0.14 0.14
Estim 4,787 4,787 285 285 1.180 1.680 605 535 2,397 0.50 3.96 4.48 762 0.14 0.16
Total 21,346 21,346 868 868 2.460 2.460 2,695 2,385 6,915 0.32 2.57 2.90 3,022 0.12 0.14
Grand Total 16,129 70,620 86,749 534 2,672 3,206 3.020 2.710 2.710 12,923 11,649 25,283 0.29 1.96 2.17 14,444 0.12 0.14

The work done during the 5 months when these analyzed cost figures were kept includes 280 ft. of bench and 220 ft. of heading. This excess of bench over heading causes the general average amounts per cubic yard to be too low.

[E]Actual amount of excavation.

[F] Amount of excavation paid for.

Span Twin Tunnels Details of Method of Drilling and Blasting 24' 6" Span Twin Tunnels Details of Method of Drilling and Blasting in a Typical (Not Exact Average) Section
Fig. 5.
Click to view larger image.
Drilling and Firing Data for Each Sub-division of Section Drilling and Firing Data for Total Sections
Sub- divisions Volume of each sub- division paid for No. of sets No. of holes in set No. times fired Total lbs. of power per hole fired Linear feet of tunnel broken Total length drilled Total length of similar headings Length drilled per linear foot of tunnel Cu yds per linear foot of tunnel Total feet drilled per cubic yard Total lbs. of power per linear foot of tunnel Total lbs. of power per foot drilled Total lbs. of power per cubic yard
a b c d e f g h i j k l m n o
A 17.775 [G]1 6 3 4.50 S(c+d) ÷ g (b+i) ÷ g j ÷ k (c+d+f) ÷ g m ÷ j m ÷ k
[H]1 9 1 1.50
[I]1 6 1 1.00
[J]1 6 1 0.75 6.0 195 2 65.00 5.925 10.97 17.00 0.261 2.848
A' 1.00 2 3-4 1 0.25 5.0 21 2 8.40 0.400 21.00 0.70 0.166 1.750
B 5.925 [G]2 3-4 1 1.00 4.0 35 2 17.50 2.962 5.90 3.50 0.200 1.181
C [K]1 3 2 1.125
33.33 4 7 1 1.125 5.0 186 1 37.20 6.666 5.58 6.975 0.187 1.046
D 6.665 2 5-6 1 0.75 3.0 33 2 22.00 4.444 4.95 5.500 0.250 1.237
Total for Heading 150.10 20.397 7.81 33.675 0.227 1.778
E 50.00 9 5 1 1.50 5.0 405 1 81.00 10.000 8.10 13.500 0.167 1.350
F 88.88 10.5 4 2 1.50
[L]5.0 4 1 1.50 4.0 682 1 170.50 22.222 7.67 23.230 0.136 1.046
G 22.22 5.5 4 2 1.00 5.0 132 1 26.40 4.444 5.94 4.400 0.166 0.990
Total for Bench 277.90 36.666 7.56 41.150 0.150 1.133
H 9.77 5 3 1 0.50
4 6 1 0.50 6.0 156 1 26.00 1.628 15.96 3.250 0.125 1.995
I 26.66 8 5 1 1.00 6.0 252 2 84.00 4.444 18.90 13.333 0.158 3.000
Total of Trench 110.00 6.072 18.10 16.583 0.151 2.731
Total for Whole Section 548.00 63.135 8.95 91.408 0.172 1.446
Powder taken at 0.5 lb. per stick

[G] 6 Cut Holes-8 feet (Black circle)

[H] 9 First Side Rd. and Bottom-7 feet (Circle with dot in it)

[I] 6 Back Round-7 feet (Circle with line in it)

[J] 6 Top Back Round-7 feet (Circle with x in it)

[K] A' 7 Holes-3 feet (Open circle)

[L] line holes (Plus sign)

TABLE 7.—Analysis of Drilling Time on Section Gy-East.

Position in Section. Nature of Rock. No. of Drill Shifts observed for average. Average Time Taken: Feet Drilled.
Setting up. Drilling. Necessary delays. Unnecessary delays. Taking down machine. Loading and firing. Total drilling. Mucking. Total. Per shift. Per working hour.
h. m. h. m. h. m. h. m. h. m. h. m. h. m. h. m. h. m.
Heading Quartz 8 0:38 4:52 1:40 0:05 0:04 7:19 2:41 10:00 22:00 2.86
Heading Hard mica schist 1 0:15 8:00 1:45 10:00 10:00 42.0 4.20
Bench Quartz 23 1:23 5:57 2:23 0:05 0:05 0:07 10:00 10:00 25.9 2.59
Bench Medium mica schist 16 1:10 6:08 1:50 0:12 0:07 0:07 9:34 0:26 10:00 22.22 2.32
Center trench Medium mica schist 10 0:58 5:53 1:33 0:06 0:12 0:30 9:12 0:48 10:00 22.0 2.39
Center trench Soft mica schist 9 1:10 6:40 1:17 0:10 0:20 0:23 10:00 10:00 26.44 2.64
General average 67 1:08 5:58 1:53 0:07 0:09 0:12 9:27 0:33 10:00 24.1 2.54
Percentage 11.3% 59.7% 18.9% 1.1% 1.5% 2% 94.5% 5.5% 100%

TABLE 8.--Analyzed Cost of Drilling.

Item of Cost. Cost per Foot of Hole Drilled Cost per drill shift
15 ft. 4 in. 19 ft. 6 in. 24 ft. 6 in. Average. 15 ft. 4 in. 19 ft. 6 in. 24 ft. 6 in. Average.
Drilling labor $0.25 $0.28 $0.31 $0.28 $6.95 $7.75 $7.60 $7.45
Sharpening 0.02 0.02 0.01 0.016 0.58 0.42 0.34 0.43
Drill steel (5 in. per drill shift) 0.007 0.007 0.006 0.007 0.19 0.20 0.15 0.19
Drill repairs 0.02 0.02 0.02 0.02 0.61 0.59 0.42 0.54
High-pressure air [M]0.05 0.04 0.07 0.07 1.39 1.86 1.67 1.82
Totals $0.35 $0.38 $0.41 $0.385 $9.67 $10.82 $10.18 $10.43
[M] This is an estimated figure, ascertained by taking a proportion of the whole charge for plant running.

General Methods.—Whenever any considerable support was needed for the ground, segmental timbering was used. In most cases, this was supported by wall-plates at the springing line, and was set with an allowance for settlement, so that it would be clear of the work when the masonry lining was put in. As the twin-tunnel section involved the excavation of the North and South Tunnels at the same time, the cross-section of the upper part of the excavation consisted of two quadrants rising from the springing line and connected at the top by a horizontal piece from 19 to 28 ft. in length. This made a rather flat arch to support by timbering.

The timber for the segmental work was 12 by 12-in. yellow pine. In light ground the bents were spaced at 5-ft. centers, in heavy ground 2-ft. 6-in. centers.

When the soft ground in the roof was struck, posts had to be used in the heading to support the caps. When the bench was removed, the posts were replaced by others down to the bottom of the excavation. These long posts were a great hindrance to all the work, and each replacement of short posts by long ones meant a settlement of the caps; consequently, it was decided to use in the section east of the cut-and-cover, where all the ground was heavy, a temporary inner bent of segmental timber, within and reinforcing the permanent bent, and resting on separate wall-plates. This is shown by Fig. 6. These temporary bents were inside the work, and were removed as the arch was built. However, the caps settled considerably in some cases, so that it was not possible to do away with posting entirely.

In heavy ground the caps were set about 1 ft. above the neat line of the crown of the brick arch, in some cases they were set only 6 in. above, but the settlement was often more than this, causing great trouble in cutting out the encroaching timber when the arch had to be built.

Typical Section Looking East Fig. 6. Typical Section Looking East
Fig. 6.
Click to view larger image.

In the tunnels east of the cut-and-cover portion, wall-plate headings were driven (shown by areas marked Aon Fig. 5), and, when a length of wall-plate had been set, the full-width heading was advanced a foot or two at a time, the timber segmental bents being set up as soon as possible; lagging was then driven over the cap into the soft ground. Fig. 6 shows the double set of segmental bents adopted in the 15-ft. 4-in. twin tunnels east of the cut-and-cover section.

When the soft ground came down so low as to interfere with the excavation of the wall-plate headings, a small heading was driven into the soft ground on the line of the ends of the caps, and lagging was driven down from this to the wall-plate heading, as illustrated in Fig. 4.

In the 19-ft. 6-in. tunnels the wall-plate for the inner bent was supported by a side-bench, termed the "Raker" bench. This was left in position until the rest of the bench and the middle subgrade conduit trench had been excavated; it was then possible to support the caps by two rows of posts from subgrade level, take out the inner bents, and excavate the raker bench.

The 24-ft. 6-in. twin tunnels, which are at the extreme eastern end of this section, adjoining the open-cut work of the Terminal Station, and under Tenth Avenue, were driven from the Terminal Station-West, and the timbering had to be made very secure on account of the pipes and sewers in the street above. Detailed records were kept of the amount of timber used and the cost of labor and material expended in timbering. These records cover the same portion of tunnel as that for which the detailed records of drilling costs, previously referred to, were kept. These records are shown in Tables 9 and 10. It will be noted that the timber used in blocking, that is, filling up voids outside the main timbering, amounted to more than two-thirds of the total timber, and that the cost of labor in erecting the timbering exceeds the prime cost of the timber by about one-third. The following distinction is made between permanent and temporary timbering: The permanent timbering is that which is concreted in when the masonry is built; the temporary consists of the lower bents and posts, which have to be removed when the masonry is built.

Force Employed in Excavation.—A typical day's working force for drilling, blasting, mucking, and timbering is shown in Table 11.

Where there was any large quantity of soft ground in the roof, the timber gang was much larger than shown in Table 11, and was helped by the mucking gang. The drillers did most of the mucking out of the heading before setting up the drills.

Excavation of Weehawken Rock Tunnels.—This subject may be dismissed in a few words, as very few features of interest were called into play. The rock was of good quality, being the sandstone typical of this part of the country. Little or no timbering was needed, there were no buildings above the tunnel to be taken care of, and large charges of powder could be used.

TABLE 9.— Supplementary Analysis of Timbering, Rock Tunnel Excavation Under 32d Street, East of Cut-and-Cover Section. Analyzed Cost of Timbering, per Foot Run and per Bent.

Ke
Per foot run of tunnel Per bent, 3 ft, 6 in., center to center Per cubic yard excavation
PERMANENT TIMBERING.
Lumber in feet, B. M.
Upper Bent. 274 685 7.8
Blocking. 294 735 8.3
Total. 568 1,420 16.1
Cost, in dollars.
Lumber. 23.75 59.38 0.67
Labor. 37.50 93.75 1.06
Total. 61.25 153.13 1.73
TEMPORARY TIMBERING.
Lumber in feet, B. M.
Lower Bent. 479 11.97 13.6
Blocking. 193 483 5.5
Total. 672 16.80 19.1
Cost, in dollars.
Lumber. 29.13 72.81 0.82
Erection labor. 28.85 72.13 0.82
Removal labor. 8.29 20.73 0.23
Total labor. 37.14 92.86 1.05
Total. 66.27 165.67 1.87
GRAND TOTAL.
Lumber in feet, B. M. 1,240 3,100 35.2
Cost, in dollars.
Lumber. 52.88 132.19 1.49
Labor. 74.64 186.61 3.60
Total. 127.52 318.80
Ki
Per foot run of tunnel Per bent, 3 ft, 6 in., center to center Per cubic yard excavation
PERMANENT TIMBERING.
Lumber in feet, B. M.
Upper Bent. 227 830 5.3
Blocking. 164 601 3.8
Total. 391 1,431 9.1
Cost, in dollars.
Lumber. 16.84 61.56 0.39
Labor. 12.82 46.88 0.30
Total. 29.66 108.44 0.69
TEMPORARY TIMBERING.
Lumber in feet, B. M.
Lower Bent. 186.33 681.25 4.33
Blocking. 42.80 156.50 0.99
Total. 229.13 837.75 5.32
Cost, in dollars.
Lumber. 9.65 35.31 0.22
Erection labor. 10.38 37.97 0.24
Removal labor. 9.74 34.09 0.23
Total labor. 20.12 72.06 0.47
Total. 29.77 107.37 0.69
GRAND TOTAL.
Lumber in feet, B. M. 6.20 22.69 14.4
Cost, in dollars.
Lumber. 26.49 96.87 0.61
Labor. 32.94 118.94 0.77
Total. 59.43 215.81 1.38
Ko
Per foot run of tunnel Per bent, 3 ft, 6 in., center to center Per cubic yard excavation
PERMANENT TIMBERING.
Lumber in feet, B. M.
Upper Bent. 261 962 4.1
Blocking. 408 1,508 6.5
Total. 669 24.70 10.5
Cost, in dollars.
Lumber. 28.00 103.38 0.44
Labor. 29.79 110.00 0.47
Total. 57.79 213.38 0.91
TEMPORARY TIMBERING.
Lumber in feet, B. M.
Lower Bent. 350 1,291 5.5
Blocking. 61 227 1.0
Total. 411 1,518 6.5
Cost, in dollars.
Lumber. 18.45 68.16 0.29
Erection labor. 20.83 76.92 0.33
Removal labor. 12.16 44.59 0.19
Total labor. 32.99 121.51 0.52
Total. 51.44 189.67 0.81
GRAND TOTAL.
Lumber in feet, B. M. 1,080 3,988 17.1
Cost, in dollars.
Lumber. 46.45 171.54 0.73
Labor. 62.78 231.50 0.99
Total. 109.23 403.04 1.72

TABLE 10.—Timbering:—Detailed Cost of Timber, Labor, and Superintendence. Rock Tunnel Excavation under 32d Street, East of Cut-and-Cover Section.

Date. Timber Used, in Feet, B.M. Excavation in Cubic Yards. Cost of Timber. Cost of Labor. Total Cost. Cost per Cubic Yard (Actual). Cost per Cubic Yard (Paid for). Cost, per 1,000 Ft., B.M., of Total Timber.
Main timber. Blocking timber. Total timber. Actual. Paid for. Main. Block. Total. Timber. Labor. Total. Timber. Labor. Total. Total timber. Labor. Total.
1907 a b c d e f g h i j h / d i / d j / d h / e i / e j / e h / c i / c j / c
Ke May 18,016 15,234 33,250 1,736 1,664 $810 $565 $1,375 $1,792 $3,167 $0.79 $1.03 $1.82 $0.82 $1.07 $1.90 $41.35 $53.89 $95.24
June 14,048 11,528 25,576 809 698 680 457 1,087 1,576 2,663 1.34 1.95 3.29 1.55 2.25 3.81 42.50 61.62 104.12
July 20,092 7,339 27,431 1,022 960 900 300 1,200 1,580 2,780 1.16 1.55 2.72 1.25 1.64 2.89 43.74 57.60 101.34
August 6,485 2,632 9,117 743 716 290 110 400 300 700 0.53 0.40 0.94 0.57 0.41 0.98 43.87 32.90 76.77
Sept. 1,632 2,224 3,856 238 238 73 94 167 60 227 0.70 0.25 0.95 0.70 0.25 0.95 43.31 15.56 58.87
Removal 663 663
Total 60,273 38,957 99,230 4,548 4,276 $2,703 $1,526 $4,229 $5,971 $10,200 $0.91 $1.51 $2.22 $1.00 $1.40 $2.40 $42.62 $60.19 $102.81
Ki May 3,537 3,537 614 527 $150 $150 $100 $250 $0.24 $0.16 $0.40 $0.28 $0.19 $0.47 $42.41 $28.27 $70.68
June 300 300 357 259 $14 14 44 58 0.04 0.12 0.16 0.05 0.17 0.22 46.66 146.33 193.33
July 7,776 5,811 13,587 530 404 350 233 583 525 7,108 1.10 0.99 2.09 1.44 1.30 2.74 42.91 38.64 81.54
August 19,712 5,702 25,414 925 890 887 220 1,107 1,018 2,125 1.20 1.10 2.30 1.24 1.14 2.38 43.56 40.06 83.61
Sept. 20,556 9,218 29,774 1,585 1,501 925 325 1,250 1,028 2,278 0.79 0.65 1.44 0.83 0.68 1.51 41.98 34.53 76.51
Removal 1,669 1,407 1,139 1,139 0.68 0.68 0.81 0.81
Total 48,344 24,268 72,612 5,680 4,988 $2,176 $928 $3,104 $3,854 $6,958 $0.55 $0.68 $1.23 $0.63 $0.77 $1.40 $42.75 $53.09 $95.84
Ko May 4,332 8,788 13,120 250 188 $175 $366 $561 $303 $864 $2.24 $1.21 $3.45 $3.00 $1.61 $4.61 $42.76 $23.10 $65.86
June 7,132 10,017 17,149 496 347 324 396 720 562 1,282 1.45 1.18 2.58 2.07 1.61 3.68 41.98 32.77 74.75
July 3,070 200 3,270 626 606 134 10 144 156 300 0.23 0.25 0.48 0.23 0.26 0.49 44.04 47.70 91.74
August 10,704 2,102 12,806 718 709 481 80 561 727 1,288 0.78 1.01 1.79 0.80 1.02 1.82 43.80 56.77 100.57
Sept. 2,400 245 2,645 396 324 108 8 116 400 516 0.29 1.01 1.30 0.36 1.23 1.59 43.85 151.23 195.08
Removal 209 211 535 535 2.56 2.56 2.54 2.54
Total 27,638 21,352 48,990 2,695 2,385 $1,242 $860 $2,102 $2,683 $4,785 $0.78 $1.00 $1.78 $0.88 $1.12 $2.00 $42.91 $54.75 $97.65
Grand total 136,255 84,577 220,832 12,923 11,649 $6,121 $3,314 $9,435 $12,508 $21,943 $0.73 $0.97 $1.70 $0.81 $1.07 $1.88 $42.73 $56.65 $99.38

Work was begun on September 1st, 1904, immediately on the completion of the work on the shaft. The North and South Tunnels in this case are completely independent, as will be seen from Plate XXXIV. The procedure adopted was to drive a top heading on the center line of each tunnel and to break down the bench from this. The drilling was at first supplied with steam power from a temporary plant, as the contractor was at that time installing his permanent plant, which was finished at the end of November, 1904. At this time the rate of advance averaged 3½ lin. ft. of full section per day of 24 hours. By the end of January the Weehawken rock tunnels were completely excavated, and by the middle of April, 1905, the excavation for the shield chambers was finished; the erection of the shields was started at the end of that month.

TABLE 11.

Grade. Total No. Rate per day. Drilling and blasting: No. Mucking: No. Timbering: No.
Superintendent 1 $7.70 ½ ? ?
Assistant engineer 1 5.80 ½ ? ?
Electrician 1 3.50 ½ ? ?
Engineer 1 3.50 1
Signalman 1 2.00 1
Foreman 3 4.00 1 1 1
Driller 5 3.00 5
Driller's helper 5 2.00 5
Laborers 14 2.00 14
Timbermen 3 3.00 3
Timbermen's helpers 4 2.00 4
Machinist 1 4.00 1
Blacksmith 2 3.50 2
Blacksmith's helper 2 2.00 2
Nipper 2 2.00 2
Waterboy 1 2.00 1
Total 47 20½ 17? 9?

The general scheme of excavation is shown by Plate XXXIII. The bench was kept 50 or 60 ft. behind the face of the heading. The powder used was 60% Forcite. The general system of drilling was as shown in Fig. 7. The average length of hole drilled per cubic yard of excavation was 2.9 ft., as against 7.70 ft. at Manhattan; and the amount of powder used was 1.96 lb. per cu. yd., as against 1.24 lb. at Manhattan. There was little timbering. A length of about 30 or 40 ft. adjoining the Weehawken shaft was timbered, and also a shattered seam of about 17 ft. in width between Stations 262+10 and 262+27.

Land Tunnels Typical Method of Drilling Used in the Weehawken Tunnels Fig. 7 Land Tunnels Typical Method of Drilling Used in the Weehawken Tunnels
Fig. 7.
Click to view larger image.

The two entirely separate tunnels gave a cross-section which was much more easily timbered than the wide flat span at Manhattan, and the segmental timbering was amply strong without posts or other reinforcement.

Table 12 is a summary of the cost of excavating the Land Tunnels, based on actual records carefully kept throughout the work.

TABLE 12.—Cost of Excavation of Land Tunnels, in Dollars per Cubic Yard.

Manhattan. Weehawken. Total yardage and average cost.
Cubic yards excavated 43,289 8,311 51,600
Labor.
Surface transport $0.49 $0.87 $0.55
Drilling and blasting 2.37 1.55 2.24
Mucking 2.49 2.08 2.42
Timbering 0.87 0.18 0.76
Total labor $6.22 $4.68 $5.97
Material.
Drilling $0.15 $0.15 $0.15
Blasting 0.21 0.21 0.21
Timber 0.39 0.20 0.36
Total material $0.75 $0.56 $0.72
Plant running $0.76 $0.65 $0.74
Surface labor, repairs and maintenance 0.15 0.08 0.14
Field office administration 1.05 1.18 1.07
Total field charges $8.96 $7.15 $8.64
Chief office administration $0.34 $0.38 $0.34
Plant depreciation 0.66 1.01 0.72
Street and building repairs 0.27 0.23
Total average cost per cubic yard $10.23 $8.54 $9.93

Masonry Lining of Land Tunnels.

Plates XXXII and XXXIV show in detail the tunnels as they were actually built. It will be seen that in all work, except in the Gy-East contract, there was a bench at each side of each tunnel in which the cable conduits were embedded. In Gy-East the bank of ducts which came next to the middle wall was carried below subgrade, and the inner benches were omitted.

The side-walls and subgrade electric conduits were water-proofed with felt and pitch. The water-proofing was placed on the outside of the side-walls (that is, on the neat line), and the space between the rock and the water-proofing was filled with concrete. This concrete was called the "Sand-Wall."

The general sequence of building the masonry lining is shown in Fig. 8. The operations were as follows:

1.—Laying concrete for the whole height of the sand-walls, and for the floor and foundations for walls and benches up to the level of the base of the conduits;

2.—Water-proofing the side-walls, and, where there was a middle trench containing subgrade conduits, laying and water-proofing these conduits;

3.—Building concrete wall for conduits to be laid against, and, where there was a middle trench, filling up with concrete between the conduits;

4.—Laying conduits;

5.—Laying concrete for benches and middle-wall;

6.—Building haunches from top of bench to springing of brick arch;

7.—Building brick arch and part of concrete back-filling;

8.—Finishing back-filling.

The whole work will be generally described under the headings of Concrete, Brickwork, Water-proofing, and Electric Conduits.

Concrete.—The number of types and the obstructions caused by the heavy posting of the timbering made it inadvisable to use built-up traveling forms at the Manhattan side, though they were used in the Weehawken Rock Tunnels.

The specifications required a facing mixture of mortar to be deposited against the forms simultaneously with the placing of the concrete. This facing mixture was dry, about 2 in. thick, and was kept separate from the concrete during the placing by a steel diaphragm. The diaphragm was removed when the concrete reached the top of each successive layer, and the facing mixture and concrete were then tamped down together. This method was at first followed and gave good results, which was indeed a foregone conclusion, as the Weehawken shaft had been built in this way. However, it was found that as good results, in the way of smooth finish, were to be obtained without the facing mixture by spading the concrete back from the forms, so that the stone was forced back and the finer portion of the mixture came against the forms; this method was followed for the rest of the work. All corners were rounded off on a 1-in. radius by mouldings tacked to the forms. The side-bench forms were used about four times, and were carefully scraped, planed, filled at open joints, and oiled with soap grease each time they were set up. When too rough for face work they were used for sand-wall and other rough work.

PLATE XXXIV.
TRANS. AM. SOC. CIV. ENGRS.
VOL. LXVIII, No. 1155.
HEWETT AND BROWN ON
PENNSYLVANIA R. R. TUNNELS: NORTH RIVER TUNNELS.
Weehawken Tunnels Weehawken Tunnels
Plan and Longitudinal Sections
Click to view larger image.

The mixing was done by a No. 4 Ransome mixer, driven by 30-h.p. electric motors. The mixer at Manhattan was set on an elevated platform at the north end of the intercepting arch; that at Weehawken was placed at the entrance to the tunnels. The sand and stone were stored in bins above the mixers, and were led to the hoppers of the mixers through chutes. The hoppers were divided into two sections, which gave the correct quantities of sand and stone, respectively, for one batch. The water was measured in a small tank alongside. A "four-bag" batch was the amount mixed at one time, that is, it consisted of 4 bags of cement, 8¾ cu. ft. of sand, and 17½ cu. ft. of broken stone, and was called a 1 : 2½ : 5 mixture. It measured when mixed about ¾ cu. yd.

The cement was furnished to the contractor by the Railroad Company, which undertook all the purchasing from the manufacturer, as well as the sampling, testing, and storing until the contractor needed it. The Railroad Company charged the contractor $2 a barrel for this material.

The sand was required by the specifications to be coarse, sharp, and silicious, and to contain not more than 0.5% of mica, loam, dirt, or clay. All sand was carefully tested before being used. The stone was to be a sound trap or limestone, passing a 1½-in. mesh and being retained on ?-in. mesh. The contractor was allowed to use a coarser stone than this, namely, one that had passed a 2-in. and was retained on a 1½-in. mesh.

The concrete was to be machine-mixed, except in cases of local necessity. The quantity of water used in the mixture was to be such that the concrete would quake on being deposited, but the engineer was to use his discretion on this point. Concrete was to be deposited in such a manner that the aggregates would not separate. It was to be laid in layers, not exceeding 9 in. in thickness, and thoroughly rammed. When placing was suspended, a joint was to be formed in a manner satisfactory to the engineer. Before depositing fresh concrete, the entire surface on which it was to be laid was to be cleaned, washed and brushed, and slushed over with neat cement grout. Concrete which had begun to set was not to be used, and retempering was not to be allowed.

MANHATTAN TYPES. Manhattan Types
Fig. 8.
Click to view larger image.

The forms were to be substantial and hold their shape until the concrete had set. The face forms were to be of matched and dressed planking, finished to true lines and surfaces; adequate measures were to be taken to prevent concrete from adhering to the forms. Warped or distorted forms were to be replaced. Plastering the face was not allowed. Rock surfaces were to be thoroughly washed and cleaned before the concrete was deposited.

These specifications were followed quite closely.

A typical working gang, as divided among the various operations, is shown below:

Superintendence.
½ Superintendent @ $250 per month
½ Assistant engineer " 150 " "
1 Assistant superintendent " 150 " "
Surface Transport.
1 Foreman @ $2.50 per day
1 Engineer " 3.00 " "
1 Signalman " 2.00 " "
16 Laborers " 1.75 " "
3 Teams " 7.50 " "
Laying.
1 Foreman @ $4.00 per day
8 Laborers " 2.00 " "
Forms.
1 Foreman @ $4.50 per day
4 Carpenters " 3.25 " "
5 Helpers " 2.25 " "
Tunnel Transport.
¼ Foreman @ $3.25 per day
¼ Engineer " 3.00 " "
¼ Signalman " 2.00 " "
4 Laborers " 1.75 " "
Mixers.
¼ Foreman @ $3.25 per day
2 Laborers " 1.75 " "

The superintendent and assistant engineer looked after the brickwork and other work as well as the concrete. The surface transport gang handled all the materials on the surface, including the fetching of the cement from the cement warehouses.

The tunnel transport gang handled all materials in the tunnel, but, when the haul became too long, the gang was reinforced with laborers from the laying gang. Of the laying gang, two generally did the spading, two the spreading and tamping, and the remaining force dumped the concrete. The general cost of this part of the work is shown in Table 13.

The figures in Table 13 include the various items built into the concrete and some that are certificate extras in connection with the concrete, such as drains, ironwork and iron materials, rods and bars, expanded metal, doors, frames and fittings, etc.

Water-proofing.—According to the specifications, the water-proofing was to consist of seven layers of pitch and six layers of felt on the side-walls and a ½-in. layer of mastic, composed of coal-tar and Portland cement, to be plastered over the outside of the arches.

By the time the work was in hand, some distrust had arisen as to the efficiency of this mastic coating, and a great deal of study was devoted to the problem of how to apply a felt and pitch water-proofing to the arches. The difficulty was that there was no room between the rock and the arch or between the timber and the arch (as the case might be) in which to work. Several ingenious schemes of putting the felt on in layers, or in small pieces like shingles, were proposed and discussed, and a full-sized model of the tunnel arch was even built on which to try experiments, but it was finally decided to overcome the difficulty by leaving out the arch water-proofing altogether, and simply building in pipes for grouting through under pressure, in case it was found that the arch was wet.

As to the arch built through the length excavated by cut-and-cover on the New York side, it was resolved to water-proof that with felt and pitch exactly as the side-walls were done, the spandrel filling between the arches being raised in a slight ridge along the concrete line between tunnels in order to throw the water over to the sides. The portions of arch not water-proofed were rather wet, and grouting with a 1:1 mixture was done, but only with the effect of stopping large local leaks and distributing a general dampness over the whole surface of the arch.

TABLE 13.—Cost of Concrete in Land Tunnels, in Dollars per Cubic Yard.

Manhattan. Weehawken. Total yardage.
Cubic yards placed 14,706½ 3,723 18,429½
Labor. Average Cost per Cubic Yard.
Surface transport $0.31 $1.43 $0.54
Superintendence and general labor at point of work 0.31 1.31 0.51
Mixing 0.52 0.56 0.53
Laying 1.38 1.45 1.39
Tunnel transport 1.30 1.47 1.34
Cleaning 0.21 0.17
Forms: erecting and removal 1.58 1.51 1.56
Total labor $5.61 $7.73 $6.04
Material.
Cement $2.30 $2.22 $2.28
Sand 0.34 0.40 0.36
Stone 0.91 0.61 0.85
Lumber for forms 0.47 0.45 0.47
Sundry tunnel supplies 0.16 0.17 0.16
Total materials $4.18 $3.85 $4.12
Plant running $0.44 $0.44 $0.44
Surface labor, repairs and maintenance 0.25 1.24 0.44
Field office administration 0.50 1.72 0.75
Total field charges $10.98 $14.98 $11.79
Plant depreciation $0.62 $1.57 $0.81
Chief office administration 0.24 0.31 0.25
Total average cost per cubic yard $11.84 $16.86 $12.85
Cost of Miscellaneous Items in Concrete.
Manhattan. Weehawken. Average.
Cubic yards 14,706½ 3,723 18,429½
Amount, in dollars $6,184.83 $1,756.79 $7,941.62
Unit cost 0.42 0.47 0.43

The 24-ft. 6-in. tunnel adjoining the Terminal Station-West was water-proofed by a surface-rendering method which, up to the present time, has been satisfactory. Generally speaking, the arches of the Land Tunnels, though not dripping with water, are the dampest parts of the whole structure from Tenth Avenue to Weehawken, and it would seem as if some form of water-proofing over these arches would have been a distinct advantage.

There was no difficulty in applying the water-proofing on the side-walls, after a little experience had been gained as to the best methods. The specifications required the sand-wall to be covered with alternate layers of coal-tar pitch and felt, seven layers of the former and six layers of the latter, the felt to be of Hydrex brand or other equally satisfactory to the engineer. The pitch was to be straight-run, coal-tar pitch which would soften at 60° Fahr., and melt at 100° Fahr., being a grade in which distillate oils, distilled from it, should have a specified gravity of 1.105. The pitch was to be mopped on the surface to a uniform thickness of 1/16 in., and a covering of felt, previously mopped with pitch, was to be applied immediately. The sheets were to lap not less than 4 in. on cross-joints and 12 in. on longitudinal joints, and had to adhere firmly to the pitch-covered surface. This layer was then to be mopped, and another layer placed, and so on until all the layers were in place. This water-proofing was to extend from the bottom of the cable conduits to the springing of the brick arch. Where sub-track conduits were used, these were to be surrounded with their own water-proofing. The work was carried out as specified; the sand-walls were not rendered, but were built smooth enough to apply the water-proofing directly to them. They were dried with gasoline torches before the application of the pitch, and in very wet sections grooves were cut to lead the water away.

The first attempts were with the felt laid in horizontal strips. This ended very disastrously, as the pitch could not sustain the weight of the felt, and the whole arrangement slipped down the wall. The felt was then laid vertically, being tacked to a piece of horizontal scantling at the top of the sand-wall and also held by a row of planks braced against it at about half its height. A layer of porous brick was laid as a drain along the base of the water-proofing, covered by a single layer of felt to prevent it from becoming choked with concrete.

The water-proofing of the sub-track conduits was troublesome, as the numerous layers and the necessity for preserving the proper laps in both directions between adjacent layers made the whole thing a kind of Chinese puzzle. Various modifications, to suit local conditions, were made from time to time. Conduits outside the general outline of the tunnel are difficult to excavate, to lay, and to water-proof, and should be avoided wherever possible.

The usual force in water-proofing consisted of a foreman, at $3.50 per day, and nine laborers at $1.75 per day. These men not only laid the water-proofing, but transported the materials, heated the pitch, and cut up the rolls of felt. In general, two men transported material, one tended the heater, and the other six worked in pairs, two preparing the surface of the concrete sand-wall, two laying pitch, and two laying felt.

The cost of the water-proofing operation was about as shown in Table 14.

TABLE 14.— Cost of Water-Proofing, in Dollars per Square Foot.

Manhattan. Weehawken. Total.
Square feet covered 47,042 13,964 60,736
Average cost per square foot.
Labor $0.07 $0.07 $0.07
Material 0.12 0.09 0.11
Total field charges $0.19 $0.16 $0.18
Chief office and plant depreciation 0.01 0.03 0.02
Total average cost $0.20 $0.19 $0.20

Brickwork in Arches.—Owing to the heavy timbering, the brickwork at Manhattan was interfered with to a considerable extent, and the gang was always kept at work at two or more places. The work was carried up to a point where it was necessary to back-fill, or prop or cut away encroaching timbers, and then the men were moved to another place while this was being done.

The centers were set up in sets of seven, spaced 4 ft. apart. Two 14-ft. lengths of 3 by 4-in. yellow pine lagging were used with each set of ribs, with 24 by 8-in. block lagging in the crown.

All centers were set ¼ in. high, to allow for settlement, except in the 24-ft. 6-in. span, in which they were set ½ in. high. This proved ample, the average settlement of the ribs being 0.01 ft. and of the masonry, 0.003 ft. In the 24-ft. 6-in. span the ribs were strengthened with 6 by 6-in. blocking and 12 by 12-in. posts to subgrade. Great trouble was here encountered with encroaching timbering, due to the settlement of the wide flat span. Grout pipes were built in, as previously mentioned.

Each mason laid an average of 0.535 cu. yd. of brickwork per hour, or 4.28 cu. yd. per day. The number of bricks laid per mason per hour was 218, or 1,744 per day.

The bricks were of the best quality of vitrified paving brick, and were obtained from the Jamestown Brick Company, of Jamestown, N. Y. The average size was 8¾ by 3-15/16 by 2-7/16 in.; the average number per cubic yard of masonry was 408, the arches being from 19 ft. to 24 ft. 6 in. in span and from 22 to 27 in. thick. The joints were 3/16 in. at the face and averaged 9/16 in. through the arch.

The proportions for mortar were 1 of cement and 2½ of sand. One cubic yard of masonry was composed of 73.5% brick and 26.5% mortar. The volume of the ingredients in a four-bag batch was 12.12 cu. ft., and the resulting mixture was 9.54 cu. ft. The number of barrels of cement was 0.915 per cu. yd. of masonry, and about 17.7% of the mortar made was wasted. The average force employed was:

Laying.
1 Foreman @ $8.00 per day
4 Layers " 6.00 " "
8 Tenders " 2.00 " "
2 Mixers " 2.00 " "
Forms.
1 Foreman @ $4.50 per day
4 Carpenters " 3.50 " "
5 Helpers " 2.25 " "
Transport.
¼ Hoist engineer @ $3.00 per day
¼ Signalman " 2.00 " "
4 Laborers " 2.00 " "

For materials, the following prices prevailed:
Cement, $2.00 per bbl.,
Sand, $0.90 to $1.00 per cu. yd.,
Brick, $16.00 per thousand, delivered at yard,
Centers, $26.00 each,
Lagging, $45.00 per 1,000 ft. B. M.

The cost of the brickwork is given in Table 15.

TABLE 15.—Cost of Brickwork.

Manhattan. Weehawken. Total.
Cubic yards placed 4,137 790 4,927
Labor. Average Cost per Cubic Yard.
Surface transport $0.35 $1.19 $0.48
Superintendent and general labor at point of work 0.17 0.04 0.16
Laying and mixing 2.58 3.20 2.60
Forms: erection and removal 2.62 0.32 2.25
Tunnel transport 1.19 1.12 1.18
Total labor $6.91 $5.87 $6.75
Material.
Brick $6.56 $6.56 $6.56
Cement 1.76 1.75 1.76
Sand 0.20 0.28 0.22
Forms 0.92 0.98 0.98
Overhead conductor pockets 0.15 0.09 0.13
Total material $9.59 $9.66 $9.60
Plant running $0.55 $0.30 $0.51
Surface labor, repairs and maintenance 0.36 1.30 0.51
Field office administration 0.55 0.88 0.60
Total field charges $17.96 $18.01 $17.97
Chief office administration $0.60 $0.66 $0.61
Plant depreciation 0.35 0.64 0.39
Total average cost per cubic yard $18.91 $19.31 $18.97

In Table 16 the cost of grout is expressed in terms of barrels of cement used, because in the schedule of prices attached to the contract, that was the unit of payment for grout.

TABLE 16.—Cost of Grout Over Arches in Land Tunnels.
Cost, in Dollars per Barrel of Cement Used.

Manhattan. (Gy-East only.) Weehawken. Total.
Barrels used 3,000½ 261½ 3,262
Average Cost per Barrel of Cement Used.
Labor $0.55 $0.46 $0.53
Material 2.30 2.25 2.28
Field office administration 0.08 0.06 0.08
Plant and supplies 0.10 0.07 0.09
Total field charges $3.03 $2.84 $2.98
Chief office and plant depreciation 0.21 0.22 0.28
Total average cost $3.24 $3.06 $3.20

Vitrified Earthenware Conduits for Electric Cables.—The general drawings will show how the ducts were arranged, and that manholes were provided at intervals. They were water-proofed, in the case of those embedded in the bench, by the general water-proofing of the tunnels, which was carried down to the level of the bottom of the banks of ducts; and in the case of those below subgrade, by a special water-proofing of felt and pitch wrapped around the ducts themselves.

The portion of wall in front of the ducts was bonded to that behind by bonds, mostly of expanded metal, passing between the ducts. Examples of the bonding will be seen in the drawings.

The joints between successive lengths of 4-way and 2-way ducts were wrapped with two thicknesses of cotton duck, 6 in. wide, those of single-way ducts were not wrapped, but plastered with cement mortar. The ducts were laid on beds of mortar, and were made to break joints at top and bottom and side to side with the adjacent ducts. They were laid with a wooden mandrel; a square leather washer at the near end acted as a cleanser when the mandrel was pulled through.

The specifications required the ducts to be laid at the same time as the concrete and be carried up with it, but this was found to be a very awkward operation, as the tamping of the concrete and the walking of men disturbed the ducts, especially as the bonds lay across them. It was resolved, therefore, to build the portion of the wall behind the ducts first, with the bonds embedded in it at the proper heights and projecting from it, then to lay up the banks of ducts against this wall, bending the bonds down as they were reached, and finally, after all the ducts were in, to lay the concrete in front of and over the top of the ducts. Several detailed modifications of this general scheme were followed at one time or another when necessary or advisable.

The laying of ducts below subgrade was not complicated by the presence of bonds, the water-proofing caused the trouble here, as before described.

The specifications called for a final rodding after completion. A group of the apparatus used in this process is shown in Fig. 1, Plate XXXV; the various parts are identified by the following key:

Key to Fig. 1, Plate XXXV.

1.—4-way duct, for telephone and telegraph cables,
2.—2-way duct, for telephone and telegraph cables,
3.—1-way duct, for high- and low-tension cables,
4.—Plug for closing open ends of ducts,
5.—Plug for closing open ends of ducts in position,
6, 7, and 8.—Cutters for removing obstructions,
9.—Hedgehog cutter for removing grout in ducts,
10.—Rodding mandrel for multiple ducts,
11.—Laying mandrel,
12.—Rodding mandrel, with jar-link attached,
13.—Laying mandrel,
14 and 15.—Rubber-disk cleaners, used after final rodding,
16 and 17.—Sectional wooden rods used for rodding,
18.—Section of iron rods used for rodding,
19.—Jar-link,
20.—Cotton duck for wrapping joints of multiple ducts,
21.—Hook for pulling forward laying mandrel,
22.—Top view of trap for recovering lost or broken rods left in ducts.

Ordinary ¾-in. gas pipe was used for the rod, and a cutter with rectangular cross-section and rounded corners was run through ahead of the mandrel: following the cutter came a scraper consisting of several square leather washers, of the size of the ducts, spaced at intervals on a short rod. The mandrel itself was next put through, three or four men being used on the rods. All the ducts in a bank were thus rodded from manhole to manhole. When a duct was rodded it was plugged at each end with a wooden plug. A solid wooden paraffined plug was used at first, but afterward an expansion plug was used.

Very little trouble was met in rodding the power conduits, except for a few misplaced ducts, or a small mound of mortar or a laying mandrel left in. At such points a cut was made in the concrete and the duct replaced.

In the subgrade telephone and telegraph ducts east of the Manhattan Shaft, much trouble was caused by grout in the ducts. The mandrel and cutters were deflected and broke through the web of the ducts rather than remove this hard grout. Trenches had to be cut from the floor to the top of the water-proofing, the latter was then cut and folded back, and the ducts replaced. To do this, a number of ducts had to be taken out to replace the broken ones and get the proper laps. The water-proofing was then patched and the concrete replaced. This grout had not penetrated the water-proofing, but had got in through the ends of the ducts where they had not been properly plugged and protected. The duct gang, both for laying and rodding, generally consisted of

1 Foreman, at $3.50 per day,
and 9 laborers, at $1.75 per day.

When laying: 4 men were laying, 2 men mixing and carrying mortar, and 3 were transporting material. When rodding: 4 men were rodding, 2 men at adjacent manholes were connecting and disconnecting cutters and mandrels, 1 was joining up rods, and 2 men assisting generally.

The cost of this work is shown in Table 17.

The track on the surface and in the tunnels was of 20-lb. rails on a 2-ft. gauge.

The excavation was handled in scale-boxes carried on flat cars, and the concrete in 1¼-cu. yd. mining cars dumping either at the side or end.

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

TABLE 17.—Cost of Conduit Work.

Manhattan. Weehawken. Total.
Duct feet 115,962 35,155 151,117
Average Cost per Duct Foot.
Labor $0.035 $0.032 $0.034
Material 0.043 0.052 0.045
Total field charges 0.078 0.084 0.079
Chief office and plant depreciation 0.005 0.008 0.006
Total average cost $0.083 $0.092 $0.085

When the haulage was up grade, 6 by 6-in. Lidgerwood hoisting engines, with 10-in. single friction drums, and driven by compressed air from the high-pressure lines, were used. Down grade, cars were moved and controlled by hand.

The muck which came through the shaft at Manhattan was dumped into hopper bins on the surface and thence loaded into trucks at convenience. At the open cut, the muck was dumped into trucks direct. The trucking was sublet by the contractor to a sub-contractor, who provided trucks, teams, and trimmers at the pier. At Weehawken, arrangements were made with the Erie Railroad which undertook to take muck which was needed as fill. The tunnel cars, therefore, were dumped directly on flat cars which were brought up to a roughly made platform near the shaft.

The hoisting at Manhattan was by derrick at Tenth Avenue and the open cut, and by the elevator at the Manhattan Shaft. At Weehawken, all hoisting was done by the elevator in the shaft.

The sand and stone were received at the wharves by scows. At Manhattan, these materials were unloaded on trucks by an overhead traveler, and teamed to the shaft, where they were unloaded by derricks into the bins. At Weehawken, they were unloaded by an orange-peel grab bucket, loaded into cars on the overhead trestle, transported in these to the top of the shaft, and discharged into the bins.

The cement at Manhattan was trucked from the Company's warehouse, at Eleventh Avenue and 38th Street, to the shaft, where it was put into a supplementary storage shed at the top of the shaft, whence it was removed to the mixer by the elevator when needed. At Weehawken, it was taken on flat cars directly from the warehouse to the mixer.

Lighting.

Temporarily and for a short time at the start, kerosene flares were used for light until replaced by electric lights, the current for which was furnished by the contractor's generators, which have been described under the head of "Power Plant."

The lamps used along the track were of 16 c.p., and were protected by wire screens; these were single, but, wherever work was going on, groups of four or five, provided with reflectors, were used.

Pumping.

Two pumps were installed at the Manhattan Shaft. They had to handle the water, not only from the rock tunnels, but also from those under the river. One was a Deane compound duplex pump, having a capacity of 500 gal. per min., the other, a Blake pump, of 150 gal. per min. They were first driven by steam direct from the power-house, but compressed air was used later. When the power-house was shut down, an electrically-driven centrifugal pump was used. This was driven by a General Electric shunt-wound motor, Type C-07½, with a speed of 1,250 rev. per min. at 250 volts and 37.5 amperes (10 h.p.) when open, and 22.9 amperes (6 h.p.) when closed, and had a capacity of 450 gal. per min. To send the water to the shaft sump during the construction, small compressed-air Cameron pumps, of about 140 gal. per min., were used.

At the Weehawken shaft two pumps were used; these dealt with the water from the Bergen Hill Tunnels as well as that from the Weehawken Tunnels. At first a Worthington duplex pump having a capacity of about 500 gal. per min. was used. Later, this was replaced by a General Electric shunt-wound motor, Type O-15, with a speed of 925 rev. per min. at 230 volts and 74 amperes (20 h.p.) when open, and 38.5 amperes (10 h.p.) when closed. Its capacity was 240 gal. per min. During the progress of the construction, the water was pumped from the working face to the shaft by small Cameron pumps similar to those used at Manhattan. When the work was finished, a subgrade reversed-grade drain carried the water to the shaft sump by gravity.

The work in the Manhattan Land Tunnels was practically finished by May 1st, 1908, though the ventilating arrangements and overhead platform in the intercepting arch were not put in until after the River Tunnel concrete was completed, so that the work was not finished until September, 1909.

The Weehawken Land Tunnels work was finished in July, 1907, but the benches and ventilating arrangements in the Weehawken Shaft were not put in until after the completion of the Bergen Hill Tunnels, and so were not finished until August, 1909.

The reinforced concrete wall around the Weehawken Shaft, together with the stairs from the bench level of the shaft to the surface, was let as a separate contract; the work was started on September 15th, 1909, and finished by the end of December, 1909.

                                                                                                                                                                                                                                                                                                           

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