Chapter III: Part 3

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.

Transportation and Disposal.

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.

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.

RIVER TUNNELS.

The River Tunnel work, from some points of view, has the most interest. It is interesting because it is the first main line crossing of the formidable obstacle of the Hudson River, and also by reason of the long and anxiously discussed point as to whether, in view of the preceding experiences and failures to construct tunnels under that river, foundations were needed under these tunnels to keep them from changing in elevation under the action of heavy traffic.

The River Tunnels here described start on the east side of the shield chambers on the New York side and end at the east side of the shield chambers on the New Jersey side. They thus include the New York and exclude the New Jersey shield chambers, the reason for such discrimination being that the New York shield chambers are lined with cast iron while those on the New Jersey side are of the typical rock section type, as already described. The design of the tunnels and their accessories will be first described, then will come the construction of the tunnels as far as the completion of the metal lining, followed by a description of the concrete lining and completion of the work.

Design of Metal Lining.

_New York Shield Chambers._--The shield chambers may be seen on Plate XXXII, previously referred to, which shows the junction of the iron-lined tunnels and the shield chambers. They consist of two iron-lined pieces of tunnel placed side by side, with semi-circular arches and straight side-walls. The segments of the arch are made to break joint with one another by making the side-wall or column castings of two different heights, as shown in Fig. 9. The length of each ring is 18 in.

The reason for the adoption of this type of construction was the necessity for keeping the width of the permanent structure within the 60-ft. width of the street. The length of this twin structure is 28.5 ft., and the weight of the metal in it is as follows:

19 long-column arch rings at 22,802 lb. 433,238 lb.
19 short-column arch rings at 23,028 lb. 437,532 "
-------
Total weight 870,770 lb.

_General Type of River Tunnel Lining._--The main ruling type adopted for the tunnels under the Hudson River, and in the soft water-bearing ground for some distance on the shoreward side of the river lines, consists of two parallel metal-lined tunnels, circular in cross-section, each tunnel being 23 ft. outside diameter, and the two tunnels 37 ft. apart from center to center, as shown on Fig. 10. The metal lining is of cast iron (except for a few short lengths of cast steel) and of the usual segmental type, consisting of "Rings" of iron, each ring being 2 ft. 6 in. in length, and divided by radial joints into eleven segments, or "Plates," with one "Key," or closing segment, having joints not radial but narrower at the outside circumference of the metal lining than at the inside. The whole structure is joined, segment to segment, and ring to ring, by mild-steel bolts passing through bolt holes in flanges of all four faces of each segment. The joints between the segments are made water-tight by a caulking of sal-ammoniac and iron borings driven into grooves formed for the purpose on the inner edges of the flanges. The clearances between the bolts and the bolt holes are also made water-tight by using grummets or rings of yarn smeared with red lead, having a snug fit over the shank of the bolt and placed below the washer on either end of each bolt. When passing through ground more or less self-sustaining, the space outside the iron lining (formed by the excavation being necessarily rather larger than the external diameter of the lining itself) was filled with grout of 1:1 Portland cement and sand forced by air pressure through grout holes in each segment. These holes were tapped, and were closed with a screw plug before and after grouting.

Having thus stated in a general way the main ruling features of the design, a detailed description of the various modifications of the ruling type will be given.

The two main divisions of the iron lining are the "ordinary" or lighter type and the heavy type. The details of the ordinary iron are shown in Fig. 11, which shows all types of lining. It was on this design that the contract was let, and it was originally intended that this should be the only type of iron used. The dimensions of the iron are clearly shown on the drawing, and it will be seen that the external diameter is 23 ft., the interior diameter, 21 ft. 2 in., the length of each ring, 2 ft. 6 in., and the thickness of the iron skin or web, 1½ in. The bolt holes in the circumferential flanges are evenly spaced through the circle, so that adjacent rings may be bolted together in any relative position as regards the radial joints, and, as a matter of fact, in the erection of the tunnel lining, all the rings "break joint," with the exception of those at the bore segments, as will be described later. This type of iron, when the original type was modified, came to be known as the ordinary pocketless iron; that is, the weight is of the ordinary or lighter type, in contradistinction to the heavier one, which later supplanted it, and the caulking groove runs along the edges of the flanges and does not form pockets around the bolt holes, as did the groove in a later type.

Each ring is made up of eleven segments and a key piece. Of these, nine have radial joints at both ends, and are called "_A_" segments; two, called "_B_" segments, have a radial joint at one end and a non-radial joint at the other. The non-radial joint is placed next to the key, which is 12.25 in. wide at the outside circumference of the iron and 12.50 in. wide at the inside.

The web is not of uniform thickness. The middle part of each _A_ and _B_ segment is 1½ in. thick; at the distance of 6 in. from the root of each flange, the thickness of web begins to increase, so that at the root it is 2-3/8 in. thick. The web of the key plate is 1¾ in. thick.

The bolts are of mild steel, and are 1½ in. in diameter; there are 67 in one circumferential joint and 5 in each radial joint. As there are 12 such radial joints, there are altogether 60 bolts in the cross-joints, making a total of 127 bolts per ring.

This original type of ordinary iron was modified for a special purpose as follows: It was known that for some distance on either side of the river, and especially at Weehawken, the tunnels would pass through a gravel formation, rather open, and containing a heavy head of water. It was thought that, by carrying the caulking groove around the bolt holes, it would be possible to make them more water-proof than by the simple use of the red-leaded grummets. Hence the "Pocket Iron" was adopted for this situation, the name being derived from the pocket-like recess which the caulking groove formed when extended around the bolt hole. The details of this lining are shown on Fig. 11, and the iron (except for the pockets) is exactly like the pocketless type.

On the New York side, in both North and South Tunnels, two short lengths were built with cast-steel lining. This was done where unusual stresses were expected to come on the lining, namely, at the point where the invert passed from firm ground to soft, and also where the tunnels passed under the heavy river bulkhead wall.

The design was precisely the same as for the ordinary pocketless iron, and Fig. 11 shows the details. After the tunnels had entered into the actual under-river portion, several phenomena (which will be described later) led to the fear that the tunnels, being lighter than the semi-liquid mud they displaced, might be subject to a buoyant action, and therefore a heavier type of lining was designed. The length of ring, number of bolts, etc., were just the same as for the lighter iron, but the thickness of the web was increased from 1½ to 2 in., the thickness of the flanges was proportionately increased, and the diameter of the bolts was increased from 1½ to 1¾ in. This iron was all of the pocketless type, shown in Fig. 11. Table 18 gives the weights of the various types of lining.

TABLE 18.--WEIGHTS OF TUNNEL LINING, DIAMETER AND WEIGHTS OF BOLTS, ETC.

+=========+===============+========+========+=======+========+========| |Reference|Type of Lining.| Weight | Weight |Weight | Weight |Diameter| |No. | | of one | of one |of one | of one | of | | | | "A" | "B" |key, in|complete| bolts, | | | |Segment,|Segment,|pounds.|ring, in| in | | | | in | in | |pounds. |inches. | | | |pounds. |pounds. | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |---------+---------------+--------+--------+-------+--------+--------| |1 |Ordinary cast | 2,063 | 2,068 | 480 | 23,183 | 1½ | | |iron without | | | | | | | |caulking | | | | | | | |pockets. | | | | | | |2 |Ordinary cast | 2,038 | 2,043 | 469 | 22,897 | 1½ | | |iron with | | | | | | | |caulking | | | | | | | |pockets. | | | | | | |3 |Ordinary cast | 2,247 | 2,252 | 522 | 25,249 | 1½ | | |steel without | | | | | | | |caulking | | | | | | | |pockets. | | | | | | |4 |Heavy cast iron| 2,579 | 2,584 | 606 | 28,985 | 1¾ | | |without | | | | | | | |caulking | | | | | | | |pockets. | | | | | | +---------+---------------+--------+--------+-------+--------+--------+

+=========+===============+========+=======+=========+ |Reference|Type of Lining.| Weight |Weight | Total | |No. | | of 1 | of |weight of| | | | bolt, |bolts, |one ring | | | |nut, and| nuts, |(segments| | | | 2 | and | and | | | |washers,|washers| bolts), | | | | in | per | in | | | |pounds. | ring, | pounds. | | | | | in | | | | | |pounds.| | |---------+---------------+--------+-------+---------| |1 |Ordinary cast | 6.62 | 840.7 | 24,024 | | |iron without | | | | | |caulking | | | | | |pockets. | | | | |2 |Ordinary cast | 6.62 | 840.7 | 23,738 | | |iron with | | | | | |caulking | | | | | |pockets. | | | | |3 |Ordinary cast | 6.62 | 840.7 | 26,090 | | |steel without | | | | | |caulking | | | | | |pockets. | | | | |4 |Heavy cast iron| 10.50 |1,333.5| 30,319 | | |without | | | | | |caulking | | | | | |pockets. | | | | +---------+---------------+--------+-------+---------+

WEIGHTS OF VARIOUS TYPES OF LINING PER LINEAR FOOT OF TUNNEL.

+---------+---------------+--------------+-------------+---------------+ |Reference|Type of Lining.|Weights of |Weights of |Weights of | |No. | |complete rings|bolts, nuts, |segments and | | | |(segments |and washers, |bolts in tunnel| | | |only), in |in pounds. |complete, in | | | |pounds. | |pounds. | |---------+---------------+--------------+-------------+---------------| |1 |Ordinary cast | 9,273.0 | 336.3 | 9,609.6 | | |iron without | | | | | |pockets. | | | | | | | | | | |2 |Ordinary cast | 9,158.8 | 336.3 | 9,495.2 | | |iron with | | | | | |pockets. | | | | | | | | | | |3 |Ordinary cast | 10,099.6 | 336.3 | 10,436.0 | | |steel without | | | | | |pockets. | | | | | | | | | | |4 |Heavy cast iron| 11,594.0 | 533.4 | 12,127.6 | | |without | | | | | |pockets. | | | | +=========+===============+==============+=============+===============+

The weights in Table 18 are calculated by assuming cast iron to weigh 450 lb. per cu. ft., and cast steel 490 lb. In actual practice the "ordinary" iron was found to weigh a little more than the weights given, and the "heavy" a little less.

The silt in the sub-river portion averaged about 100 lb. per cu. ft., so that the weight of the silt displaced by the tunnel was about 41,548 lb. per lin. ft.

_Taper Rings._--In order to pass around curves (whether horizontal or vertical), or to correct deviation from line or grade, taper rings were used; by this is meant rings which when in place in the tunnels were wider than the standard rings, either at one side (horizontal tapers or "Liners"), or at the top ("Depressors"), or at the bottom ("Elevators").

In the original design a ½-in. taper was called for, that is, the wide side of the ring was ½ in. wider than the narrow side, which was of the standard width of 2 ft. 6 in. As a matter of fact, during construction, not only ½-in., but ¾-in. and 1-in. tapers were often used.

These taper rings necessitated each plate having its own unalterable position in the ring, hence each plate of the taper ring was numbered, so that no mistake could be made during erection.

The taper rings were made by casting a ring with one circumferential flange much thicker than usual, and then machining off this flange to the taper. This was not only much cheaper than making a special pattern for each plate, but made it possible to see clearly where and what tapers were used in the tunnel.

Taper rings were provided for all kinds of lining (except the cast steel), and the lack of taper steel rings was felt when building the steel-lined parts of the tunnel, as nothing could be done to remedy deviations from line or grade until the steel section was over and cast iron could again be used. Table 19 gives the weights of the different kinds of tapers used.

TABLE 19.--WEIGHTS OF CAST-IRON TAPER RINGS, IN POUNDS PER COMPLETE RING.

=================================+======================================
Classification. |Weight of cast iron per complete ring,
| in pounds.
---------------------------------+--------------------------------------
Ordinary pocketless ½- in. taper| 23,767.7
" " 1- " " | 24,352.4
" pocket ½- " " | 23,481.7
Heavy pocketless ½- in. taper | 29,564.8
" " ¾- " " | 29,854.7
" " 1- " " | 30,144.6
=================================+=======================================

_Cast-Steel Bore Segments and Accessories._--The following feature of these tunnels is different from any hitherto built. It was the original intention to carry the rolling load independent of the tunnel, or to assist the support of the silt portion of the structure by a single row of screw-piles, under each tunnel, and extending down to firmer ground than that through which the tunnels were driven. Therefore, provision had to be made whereby these piles could be put down through the invert of the tunnel with no exposure of the ground.

This provision was afforded by the "Bore Segments," which are shown in detail in Fig. 12. There are two segments, called No. 1 and No. 2, respectively. These two segments are bolted together in the bottom of two adjacent rings, and thus form a "Pile Bore." As the piles were to be kept at 15-ft. centers, and as the tunnel rings were 2 ft. 6 in. in length, it will be seen that, between each pair of bore-segment rings, there came four "Plain" rings. The plain rings were built up so that the radial joints broke joint from ring to ring, but with the bore-segment rings this could not be done, without unnecessarily adding to the types of segments.

The bore segments were made of cast steel, and were quite complicated castings, the principle, however, was quite simple. The segments provided an opening just a little larger than the shaft of the pile, the orifice being 2 ft. 7 in. in diameter at the smallest (lowest) point, while the shaft of the pile was to be 2 ft. 5¼ in. In order to allow of the entry of the screw-blade or helix of the pile, a slot was formed in the depth of Bore Segment No. 1, so that, when a pile was put in position above the bore, the blade, when revolved, would enter the slot and thus pass under the metal lining, although the actual orifice was only slightly larger than the pile shaft.

The wall of the pile orifice in Segment No. 2 was made lower than that in No. 1 so as to allow the blade to enter the slot in Segment No. 1. When the pile is not actually in process of being sunk, this lower height in No. 2 is made up with the removable "distance piece." This had a tongue at one end which engaged in a recess cast to take it in Segment No. 2 and was held in place by a key piece at the other end of the distance piece. Details of the distance piece and key are shown in Fig. 12.

The flanges around the pile bore were made flat and furnished with twelve tapped holes, six in Segment No. 1 and six in Segment No. 2, for the purpose of attaching the permanent arrangements in conjunction with which the pile was to be attached to the track system, independently of the tunnel shell, or directly to the tunnel. It was never decided which of these alternatives would be used, for, before this decision was reached, it was agreed that, at any rate for the present, it was better not to put down piles at all.

To close the bore, the "Bore Plug" was used. This is shown on Fig. 12. It was of cast steel, and was intended to act as a permanent point of the screw-pile, that is, the blade section was to be attached to the bore plug, the distance piece and key were to be removed, and the pile was to be rotated until the blade had cleared the slot; the distance piece and key were then to be replaced and sinking resumed.

The plug was held in place against the pressure of the silt by the two "dogs," while the dogs themselves were attached to the tunnel, as shown in Fig. 12. The ends of the dogs, which rested on the flanges of the metal lining of the tunnel, were prevented from being knocked off the flanges (and thus releasing the plug) by steel clips.

It was expected that it might be desirable to keep the lower end of the piles open during their sinking, so that the bore plugs were not made permanently closed, but a seating was formed on the inner circumference of the plug, and on the seating was placed the "Plug Cover," made of cast iron, 18¾ in. in diameter and 3 in. thick, furnished with a lug for lifting and a 3-in. tapped hole closed by a screw-plug, through which any soundings or samples of ground could be taken prior to sinking the piles. This plug cover was held in place by a heavy steel "Yoke" under it, which engaged on the under side of the flange, on top of which the cover was set. The yoke was attached to the cover by a 1¾-in. tap-bolt, screwed into the yoke and passing through a 2-in. hole bored in the center of the cover. This rather peculiar mode of attaching the cover was adopted so that the cover could be removed by taking off the nut of the yoke, in case it was desired to open the end of the pile during the process of sinking.

The plug was a fairly close fit at the bottom of the orifice, that is, at the outside circumference of the tunnel, where the bore was 2 ft. 7 in. in diameter and the plug 2 ft. 6¾ in., but at the top of the bore-segment there was more clearance, as the plug was cylindrical while the bore tapered outward. To fill this space, it was intended that steel wedges should be used while the shield was being driven, so that they would withstand the crushing action of the thrusting shield, and, when the shield was far enough ahead, that they should be removed and replaced by hardwood wedges. This method was only used in the early weeks of the work; the modification of not using the shield-jacks which thrust against the bore segments was then introduced, and the wooden wedges were put in, when the bore plugs were set in place, and driven down to the stage of splitting.

When it was resolved not to sink the screw-piles, the bores had to be closed before putting in the concrete lining. This was done by means of the covers shown in Fig. 13. The bore plug and all its attachments were removed, and the flat steel cover, 2 in. thick and with stiffening webs on the under side, was placed over the circular flanges of the pile bore. The cover was attached to the bore segments by twelve 1½-in. stud-bolts, 6 in. long, in the bolt holes already mentioned as provided on these flanges.

When these were in place, with lead grummets under the heads of the bolts, and the grooves caulked, the bore segments were water-tight, except in Bore Segment No. 2, at the joint of the distance piece; and, to keep water from entering here, this segment was filled to the level of the top of the flanges with 1:1 Portland cement mortar.

The weights of the various parts of the bore segments are given in Table 20.

TABLE 20.--WEIGHTS OF BORE SEGMENTS AND ACCESSORIES, IN POUNDS.

====================+=====+==================================== Part. | No. | Material. | Weight, in pounds. --------------------+-----+---------------+-------------------- Bore Segment No. 1 | 1 | Cast Steel | 3,004.0 Bore Segment No. 2 | 1 | " " | 2,628.0 Distance piece | 1 | " " | 423.5 Key | 1 | " " | 34.3 Plug | 1 | " " | 1,192.5 Yoke | 1 | " " | 57.3 Dogs | 2 | " " | 106.0 Slot cover | 1 | Rolled steel | 6.4 Plug cover | 1 | Cast iron | 162.0 Dog holders | 2 | Rolled steel | 6.4 --------------------+-----+---------------+-------------------- Complete weight of one pair, without bolts| 7,620.4 ==========================================+====================

_Sump Segments._--In order to provide sumps to collect the drainage and leakage water in the subaqueous tunnels, special "sump segments" were installed in each tunnel at the lowest point--about Station 241 + 00. The details of the design are shown in Fig. 14. The segment was built into the tunnel invert as though it were an ordinary "_A_" segment. In building the sump, three lining castings were bolted, one on top of the other, and attached to the flat upper surface of the sump segment; meanwhile, the bolts attaching the sump segment to the adjacent tunnel plates were taken out and the plate and lining segments were forced through the soft mud by hydraulic jacks, the three 6-in. holes in the bottom of the sump segment being opened in order to minimize the resistance. The sump when built appeared as shown in Fig. 14, the top connection being made with a special casting, as shown.

The capacity of each sump is 500 gal., which is about the quantity of water entering the whole length of each subaqueous tunnel in 24 hours.

_Cross-Passages._--When the contract was let, provision was made for cross-passages between the tubular tunnels, in the form of special castings to be built into the tunnel lining at intervals. However, the idea was given up, and these castings were not made. Later, however, after tunnel building had started, the question was raised again, and it was thought that such cross-connections would be very useful to the maintenance forces, that it might be possible to build them safely, and that their subsequent construction would be made much easier if some provision were made for them while the shields were being driven. It was therefore arranged to build, at intervals of about 300 ft., two consecutive rings in each tunnel, at the same station in each tunnel, with their longitudinal flanges together, instead of breaking joint, as was usually done. The keys of these rings were displaced twelve bolt holes from their normal positions toward the other tunnel. This brought the keys about 6 ft. above the bench, so that if they were removed, together with the _B_ plates below them, an opening of about 5 by 7 ft. would be left in a convenient position with regard to the bench.

Nothing more was done until after the tunnels were driven. It was then decided to limit the cross-passages between the tubular tunnels to the landward side of the bulkhead walls. They were arranged as follows: three on the New York side, at Stations 203 + 22, 206 + 80, and 209 + 80, and two on the New Jersey side, at Stations 255 + 46 and 260 + 14. The cross-passages are square in cross-section.

TABLE 21.--WEIGHTS OF SUMP SEGMENTS.

====================+=====+===============+==================== Part. | No. | Material. | Weight, in pounds. --------------------+-----+---------------+-------------------- Middle top casting | 1 | Cast steel | 880 End top castings | 2 | " " | 1,718 Lining castings | 3 | " " | 18,232 Sump segment | 1 | Cast iron | 3,560 --------------------+-----+---------------+-------------------- Total weight per sump, exclusive of bolts | 24,390 ==========================================+====================

_Turnbuckle Reinforcement for Cast-Iron Segments._--During the period of construction, a certain number of cast-iron segments, mostly in the roof, but in some cases at Manhattan in the invert, behind the river lines, became cracked owing to uneven pressures of the ground. Before the concrete lining was put in, considerable discussion occurred as to the wisest course to pursue with regard to these broken plates. It was finally thought best not to take the plates out, as more harm than good might be done, but to reinforce them with turnbuckles, as shown in Fig. 15. The number of broken segments was distributed as follows:

North Manhattan Tunnel 87, chiefly in silt (not under the river),
South Manhattan Tunnel 7, chiefly in silt ( " " " " ),
North Weehawken Tunnel 24, chiefly in sand ( " " " " ),
South Weehawken Tunnel 48, chiefly in silt, under the Fowler
Warehouse.

The chief features of the tunnel lining have now been described, and, before giving any account of the methods of work, it will be well to mention briefly the salient features of the concrete lining which is placed within the actual lining.

Design of Concrete Lining.

This concrete lining will be considered and described in the following order:

The New York Shield Chambers,

Standard Cross-Section of Concrete Lining of Shield-Driven
Tunnels,

Final Lines and Grades, and How Obtained,

Steel Rod Reinforcement of Concrete,

Cross-Passage Lining,

Special Provision for Surveys and Observations.

_The New York Shield Chambers._--The cross-section of the concrete lining of these chambers is shown by Plate XXXII, referred to in the Land Tunnel Section. They are of the twin-tunnel double-bench type. The deep space beneath the floor is used as a sump for drainage, and manholes for access to the cable conduits are placed in the benches.

_Standard Cross-Section of Concrete Lining of Shield-Driven Tunnels._--The cross-section of the concrete lining of the tube tunnel is shown in Fig. 16. There are two main types, one extending from the shield chambers to the first bore segment, that is, to where the tunnel leaves solid ground and passes into silt, and the other which extends the rest of the way. The first type has a drain in the invert, the second has not.

The height from the top of the rail to the soffit of the arch being less than 16 ft. 11 in., overhead pockets for the suspension of electrical conductors were set in the concrete arch on the vertical axis line at 10-ft. centers. These pockets are shown in Fig. 16. The benches are utilized for the cable conduits in the usual way. Ladders are provided on one side at 25-ft. and on the other side at 50-ft. intervals, to give access from the track level to the top of the benches. Refuge niches for trackmen are placed at 25-ft. intervals on the single-way conduits side only, as there is not enough room in front of the 4-way ducts. Manholes for giving access to the cable conduits, both power, and telephone and telegraph, are at 400-ft. intervals.

_Final Lines and Grades, and How Obtained._--It may be well to explain here how the final lines and grades for the track, and therefore for the concrete lining, were obtained and determined. It is first to be premised that the standard cross-section of the tunnel (that is, of the concrete and iron lining combined) is not maintained throughout the tunnel. In other words, the metal lining is of course uniform, or practically so, throughout; the interior surface of the concrete lining is also uniform from end to end, but the metal lining, owing to the difficulty of keeping the shields, and hence the tunnels built within them, exactly on the true line and grade, is not on such lines and grades; the concrete lining is built exactly on the pre-arranged lines and grades, consequently, the relative positions of the concrete and metal linings vary continually along the length of the structure, according to whether the metal lining is higher or lower than it should be, further to the north or to the south, or any combination of these.

As before stated, it was strongly desired to encroach as little as possible on the standard 2-ft. concrete arch, and after some discussion it was decided that a thickness of 1 ft. 6 in. was the thinnest it was advisable to allow. This made it possible to permit the metal lining of the tunnel to be 6 in. lower, in respect to the level of the track at any point, than the standard section shows, and also allowed the center line of the track to have an eccentricity of 6 in. either north or south of the center line of the tunnel. This only left to be settled the extent to which the metal lining might be higher in respect to the track than that shown on the standard section.

This amount was governed by the desirability of keeping sufficient clearance between the top of the rail and the iron lining in the invert to admit of the attachment of pile foundations and all the accompanying girder-track system which would necessarily be caused by the use of piles, should it ever become apparent after operation was begun, that, after all, it was essential to have the tunnels supported in this way. Careful studies were made of the clearance necessary, and it was decided that 4 ft. 9 in. was the minimum allowable depth from the top of the rail to the outside of the iron at the bottom. This meant that the iron lining could be 3 in. higher, with respect to the track level, than that shown on the standard section.

All the determining factors for fixing the best possible lines and grades for the track within the completed metal lining were now at hand. In March, 1908, careful surveys of plan and elevation were made of the tunnels at intervals of 25 ft. throughout. The following operations were then performed to fix on the best lines and grades:

First, for Line: It has been explained that the permissible deviation of the center line of the track on either side of the center line of the tunnel was 6 in. Had the metal lining been invariably of the true diameter, it would have been necessary to survey only one side of the tunnel; this would have given a line parallel to the center line, and might have been plotted as such; then, by setting off 6 in. on either side of this line, there would have been obtained a pair of parallel lines within which the center line of the track must lie. Owing to variations in the diameter of the tunnel, however, such a method was not permissible, and therefore the following process was used:

When running the survey lines through the tunnel (which were the center lines used in driving the shields), offsets were taken to the inner edges of the flanges of the metal lining, both on the north and south sides, at axis level at each 25-ft. interval. On the plat on which the survey lines were laid down, and at each point surveyed, a distance was laid off to north and south equal to the following distances:

Offset, as measured in the tunnel to north (or south), minus 10.08 ft.

This 10.08 ft. (or 10 ft, 1 in.) represents 10 ft. 7 in., the true radius to inside of iron, minus 6 in., the permissible lateral deviation of the track from the axis of the tunnel.

The result of this process was two lines, one on either side of the survey lines, not parallel to it or to each other, but approaching each other when the horizontal diameter was less than the true diameter, receding from each other when the diameter was more, and exactly 12 in. apart when the diameter was correct. As long as the center line of the track lay entirely within these two limiting lines, the condition that the concrete arch should not be 6 in. less in thickness than the standard 2 ft. was satisfied, and in order to arrive at the final line, the longest possible tangents that would be within these limits were adopted as the final lines; and, as the survey lines were those used in driving the tunnel shields (that is, the lines to which it was intended that the track should be built), the amount by which the new lines thus obtained deviated from the survey lines was a measure of the deviation of the finally adopted track and concrete line from the original contract lines.