Part 7
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").