Sand-Walls.—The sand-wall forms first used are shown in Fig. 2, Plate XXIV, with a section of the finished sand-wall. As this work was only intended to give a comparatively smooth surface against which to place the water-proofing, no particular care was taken with the surface, except to avoid sharp projections which might cut through the felt and pitch used for this purpose. A rather porous concrete (with all the rock which could be safely embedded in it and have the wall stand) was used, so that it would not act as a dam, but rather tend to allow the water to find its way to the bottom of the tunnel, and so into the drains.
The traveling gantry for placing the concrete in the sand-walls, as first designed, with the belt conveyor, could of course only deliver the concrete at one end. Before setting the forms for a new section, it was necessary, therefore, to move the gantry ahead, before the cross-bracing between the tops of the forms, which also held the top platform, could be placed in position. Fig. 2, Plate XXIV, shows the end of the conveyor over the top of the cross-braces. In order to hold the bottom of these forms, small wooden blocks were embedded in the foundation concrete, against which they could be wedged, as shown by Fig. 13, A; these blocks were cut out after the sand-wall had been built.
After the forms had been filled, the conveyor could not be moved back to the bench-wall until the concrete had set sufficiently so that these cross-braces could be removed, and, on account of the overhang at the top, the set had to be fairly good in order to prevent this overhang from breaking off. This arrangement, therefore, for placing the concrete was found to be impractical, if the proposed schedule of a section of bench-wall and a section of sand-wall to be built on alternate days, was to be carried out. In a few instances, where the sand-wall was finished fairly early in the afternoon, the forms were released next morning, and the conveyor was moved back, but, even then, 2 or 3 hours at least were lost at the beginning of the shift. The conveyor, however, was abandoned, for the reasons previously given, and the traveling gantry was rearranged to allow concrete to be delivered at either end; it was then only necessary to move it backward and forward between the bench- and sand-wall forms instead of through these forms. This permitted the construction of the much more substantial type of forms shown by Fig. 14.
After being moved ahead on the track on top of the foundation, the form was first blocked up to grade, and then adjusted to line by the screws and slotted cleats shown at B, Fig. 14, after which it was secured by the braces from the ditches, as shown. The face lagging was placed in separate pieces and held against the uprights by lightly nailing every third or fourth piece; the whole was removed each time the form was moved, and built up again as the concrete was placed.
Considerable care was taken to slope the top of the sand-wall back toward the rock, as shown by Fig. 14, and to allow free drainage along the top (which ran parallel to the grade of the tunnel) to the 4-in. cast-iron drain pipes which carried the water from the rock packing above the arch to the drains beneath the track.
Sand-walls were built for a length of about 1,100 ft. in each tunnel at the Weehawken end, and about 700 ft. in each tunnel at the western end, the remainder of the work, with the exception of a few short stretches, not being considered wet enough to require water-proofing.
Conduits.—The arrangement of the conduit lines is shown in the general cross-section. On the core-wall side there are 48 lines for telegraph and telephone cables, built of 4-way multiple conduit, each piece of which is 3 ft. long and about 10 in. square outside. On the other side there are the high- and low-tension lines, built of single conduit 18 in. long and a little more than 5 in. square outside. Manholes or splicing chambers are built every 400 ft., and are about 8 ft. long and 4 ft. wide. General views of the conduits as built are shown in Fig. 4, Plate XXV, which shows all the lines in one tunnel, and in Fig. 1, Plate XXV, which shows the telegraph and telephone lines, with the expanding mandrels used in laying them.
[Footnote 3: Plate VIII in the paper by Mr. Jacobs.]
[Illustration: Plate XXV. Fig. 1: K 173. P.R.R. Tunnels, N. R. Div. Sect. K. (Bergen Hill Tunnels.) Hackensack Portal and Approach. Telephone and Telegraph ducts and mandrels. Nov. 20, 08. Fig. 2: K 125. P.R.R. Tunnels, N. R. Div. Sect. K. (Bergen Hill Tunnels) Weehawken Shaft, North Tunnel. View showing general construction of tunnel lining forms, and clearance to allow disposal of excavated material. June 17, 07. Fig. 3: K 156. P.R.R. Tunnels, N. R. Div. Sect. K. (Bergen Hill Tunnels) Weehawken Shaft, South Tunnel. North side looking East, showing method of placing waterproofing. Oct. 22, 07. Fig. 4: K 147. P.R.R. Tunnels, N. R. Div. Sect. K. (Bergen Hill Tunnels) Weehawken. General view showing center and first section of arch and completed lining, North Tunnel. Sept. 24, 07.]
In attempting to plan the work of placing the lining, two methods of building the bench-wall were considered. One was to build the wall in longitudinal sections, each section separated by a line of ducts; and the other was to attempt to build the wall in the manner called for by the specifications, which required the concrete to be carried up in layers as the conduits were laid. In this latter method, it was proposed to bond the concrete together with the forked bonds, the details of which are shown by Fig. 15, A, but, as it might have been impractical to use these if the wall had been built in sections, provision was made in the contract to place expanded metal, as shown by Fig. 15, B, if this was thought advisable. The method of construction necessary, if the wall had been built in sections, is shown graphically by the five sketches, Fig. 15, B, 1, 2, 3, 4, and 5.
The form and details of the expanding mandrel which was finally designed to meet the conditions, and proved so satisfactory in every way, are shown by Fig. 15, C. The mandrel consisted of two triangular pieces of hard pine, separated by wedges attached to one piece which fitted into slots in the other; these, when expanded, practically filled the whole of the inside of the ducts. One of these mandrels was placed in each line of single ducts and two in each 4-way duct, placed diagonally, as shown in Fig. 1, Plate XXV. This required 60 mandrels at each working point, or 240 for the whole work. The mandrels were 35 ft. long, so that they easily covered the whole of a 25-ft. section, projected sufficiently far back into the previously finished work to assure the continuity of the alignment, and allowed the ends to be racked out at the forward end to secure proper breaks between the joints.
In laying the single conduits, as a rule, the (collapsed) mandrels were pulled ahead from the previous section as each line was laid, and the conduits were strung on it until the whole length was completed; the conduits were then pushed up tight together, so as to close the joints as tightly as possible, and then the mandrel was expanded. The conduits were thus held firmly in position, and the forward end of the line was lifted slightly so that the wraps could be placed around the joints. The 4-way conduits were generally laid in the ordinary way, except that no laying mandrel was necessary. One dowel was used between each of the pieces of conduit, at the center, and the joints were wrapped. When a line was finished, two mandrels were placed diagonally in each line and expanded simultaneously, so that any inequalities in the ducts themselves were divided as far as possible. In connection with the use of these mandrels, one of the points which was most carefully watched was that they projected back into the last completed section, thus insuring the continuity of the alignment.
It was originally intended to wrap the joints of the 4-way ducts only, but it was found to be impractical to keep the grout from the wet concrete entirely out of the single ducts, and, after a short trial, it was decided to wrap these also. The expanding mandrel kept out a great deal of the cement, and, in the sections laid without wraps, the only difficulty from this cause seemed to be that a slight film of grout, from 1/16 to 1/8 in. thick, was deposited on the bottom of the inside of the ducts at some places, and although this was not considered a serious defect, it was thought that the slight extra cost of placing the wraps would undoubtedly be justified by the practically perfect results obtained by using them.
Considerable attention was given to breaking the joints of the ducts properly, so as to maintain throughout the conduit lines the greatest break possible. The joints in each superimposed line were broken at half the length of the individual pieces of conduit, the joints in lines in the same horizontal plane being broken at one-quarter the length, thus preventing any joints from touching one another either at the sides or corners, which tended to prevent a burn-out on one line from being communicated to another. There was some little difficulty at first in maintaining the breaks, owing to slight variations in the lengths of the conduit, but after a very short time both the workmen and the inspectors became very expert at this and in the proper use of short lengths to maintain the spacing; after the first few weeks there was little if any difficulty in attaining at all times almost perfect results. The method of making the breaks is shown in the photographs and by the isometric sketch at F, Fig. 15.
All the conduits used on this work were furnished by the Great Eastern Clay Company, and were made at its factory at South River, N.J., where they were inspected before shipment.
The mandrel used in the final rodding was made as shown at G, Fig. 15, the larger size being used for all lines. The rods for pushing it through the conduit lines were made of 6-ft. lengths of ordinary 1-in. wrought-iron pipe with extra long (3-in.) couplings. The lines were rodded in both directions from alternate manholes, thus avoiding uncoupling the rods and allowing every pull to be effective in pushing the mandrel through the ducts.
ELECTRICAL CONDUITS: METHODS OF LAYING, RODDING, ETC. A. FORK ENDED STEEL BONDS FOR CONDUITS. B. SEQUENCE OF METHODS OF BUILDING BENCH-WALL PROPOSED WHEN USING EXPANDED METAL BONDS. C. ISOMETRIC DRAWING OF EXPANDING MANDREL. D. DETAILS OF "WEASEL" Used for gripping disconnected pipe rods in conduit E. CUTTER FOR REMOVING OBSTRUCTIONS IN CONDUITS. F. ISOMETRIC SKETCH SHOWING METHOD OF BREAKING JOINTS AND POSITION FORKED BONDS. G. PLAN AND SECTIONS OF EXPANDING MANDREL.
INDEX - Multi-Duct Single-Duct Mandrel Mandrel - A 3" 3-3/8" B " 7/8" C 2" 2-5/8" -
End pipe connections may be changed to suit connections of rodding outfit, care being taken to use a connection which will not split and expand the mandrel if it should be driven back into it, in attempting to ram the mandrel back when stuck in a duct.
Connection at Head End may be dispensed with, if the mandrel is threaded through ducts by rods attached to the trailing end.]
Wooden rods were used at first, but proved entirely too light, as the mandrels used were a close fit, and it required considerable effort to push them through 400 ft. of conduit. Iron pipe with ordinary couplings was next tried, but the couplings broke quite often, as the threads became worn in uncoupling the sections to move the rods from one line to another, and the break was generally inside a duct line. The long couplings were finally adopted, and a set of rods was put in each line, that is, six sets in all, so that when coupled up they remained in the line until it was finished. The expense of the extra quantity of pipe thus required was more than offset by the decreased labor cost.
It was thought necessary at first to run a cutter, Fig. 15, E, through the conduits ahead of the final rodding mandrel, but this was soon found to be unnecessary except in a very few instances, and, after a short experience, the cutter was only used at places where an obstruction was encountered by the mandrel.
At such times as the pipe became uncoupled inside the duct line, the part remaining inside was recovered by the use of the tool shown at D, Fig. 15, called a "weasel." In two instances, the mandrel became stuck in such a manner that the duct line had to be cut into in order to take it out.
The best day's work of the rodding gang (1 foreman and 4 men) was 20,400 duct ft. of the 4-way conduit in the telegraph and telephone line, and 19,200 duct ft. of single conduit on the low-tension line, an average day's work under ordinary conditions being about 10,000 duct ft. The cost, including labor, material, and all tools, for rodding for the whole work was slightly less than 0.2 cent per duct ft. The average cost of the single conduit was about 0.25 cents per ft., and of the 4-way, 0.15 cents per ft. About 10% of the conduit lines were rodded twice, owing to partial sections having been rodded once before completion. The best continuous work on rodding was done between October 22d and 29th, 1908, when in 7 working days, 105,600 duct ft. were rodded, an average of a little more than 15,000 ft. per day.
Bench-walls.—The original design for the tunnels provided for the construction of a brick arch above a point 22 above the springing line, that is, the part above the side-walls (Fig. 10). It was thought desirable, therefore, in designing the bench-wall forms, to provide for placing the concrete in the side-walls and bench-walls at one operation. These forms, as first designed, are shown by Fig. 2, Plate XXV, and the details in Fig. 16, A and A'; they were built of steel, the facing plates being 5/16 in. thick, in pieces 4 ft. 6 in. wide, and in length about 6 in. more than the height of the bench-wall.
DETAILS OF TRAVELING FORMS USED IN THE CONSTRUCTION OF THE BENCH WALLS A'. CROSS-SECTION OF STEEL FORM A. LONGITUDINAL SECTION AND ELEVATION OF STEEL FORM USED AT WEEHAWKEN END B. DETAILS OF SCREW-JACKS FOR ADJUSTING FORM TO LINE C. SECTION C-D SHOWING CONNECTION OF FACE PLATES TO I-BEAM UPRIGHTS D. DETAILS OF WOODEN FORMS USED AT WESTERN END: CROSS-SECTION, PART LONGITUDINAL SECTION No chutes were used with these forms, the wheel-barrows being dumped from the runways on the sides.]
The design was controlled very largely by the necessity of providing the requisite clearance for the locomotives and muck cars, and the principal feature was the support of the forms on two trusses, one at either side, the front ends of which were supported from the foundation on a long leg, as shown in Fig. 3, Plate XXV, and the rear ends directly on the journal-boxes of wheels traveling on a rail on the top of the finished bench, as shown in Fig. 2, Plate XXV.
Although it had been decided to substitute concrete for brick in the arch before any of the lining was actually placed, two sets of forms for the Weehawken end had already been ordered and delivered, so it was decided to use them as designed, and place the side-wall with the bench.
The forms were designed so that 30-ft. lengths could be built, and this was done at the start, but owing to the occurrence of the refuge niches, ladders, etc., at 25-ft. intervals, it was soon seen that it would be advisable to build the bench-wall in sections of that length (25 ft.), or multiples of it, and as the clearance conditions seemed to preclude the possibility of making the forms 50 ft. long, 25 ft. was adopted. This permitted the removal of one of the panels, 4 ft. 6 in. wide, and at the same time it was decided to remove the side-wall forms. This decreased the load on the trusses considerably, but being still a trifle weak, they were strengthened by the substitution of 1-in. truss rods instead of the -in. rods used originally. The top platform and the cross-bracing were also stiffened a little and tightened up to prevent racking.
The construction of the side-walls in conjunction with the bench-wall was abandoned for three reasons: First, it was found that there would be a much more even distribution of the work by including the side-wall with the arch rather than with the bench; second, there was difficulty in getting a good finish for the top of the bench-wall, as of course a top form for the latter had to be placed to prevent the concrete from squeezing up when the side-wall was built above it, which prevented troweling; the third reason was the weakness of the whole form as designed, and the increasing difficulty of adjusting it to line as the work progressed, the principal difficulty being with the curved side-wall forms.
The bench-wall forms were set in position, after they had been moved ahead, by first blocking the bottom against the face of the foundation, as shown by Fig. 13. As previously noted, this foundation face had been built very carefully to line. The back end of the form, of course, was blocked tightly against the end of the previously finished section, and the top was made plumb by the adjusting screwjacks shown in Fig. 16, B. At first these screws were -in., but they were afterward changed to 1-in. The only points which it was necessary for the alignment corps to give in setting these forms was a grade at each of the front ends for the top of the finished bench.
The steel face forms in both tunnels gave excellent results, as far as smoothness of finish was concerned, but, owing to the imperviousness of the steel, small air holes were formed in the surface, though not in sufficient numbers or size to cause trouble or disfigure the work in any way.
The design of the bench-wall forms used at the western end, where this differs from the steel form, is shown by Fig. 16, D. The principal features in which they differed from those used at the Weehawken end was in the substitution of 2-in. tongued and grooved hard pine for the face. This timber was of the very best quality obtainable, each piece being especially selected and as nearly clear and free from knots or other defects as it was possible to get it. The edges of each piece were planed at the back so as to insure a tight joint on the face, and all joints were shellacked. These forms were used, without renewal of the face timber and with only two planings, for a length of 2,500 ft., or 100 separate sections, and gave good satisfaction.
In order to obtain a surface to which the face lagging could be fastened, wooden uprights were used and were reinforced on either side by light channels bolted together through the timber, in place of the I-beams used on the steel forms. The lagging was nailed to these uprights by 6-in. wire nails driven through the top edges of each piece as it was placed in position, thus leaving the surface entirely clear and free from any marks or nail holes, and in condition for planing when this became necessary. Runways for wheeling the concrete were built one either side over the bench-walls instead of having a center platform with chutes, as was used at Weehawken.
When the original lagging had become too much worn for further use, it was resurfaced with strips of 7/8 by 2-in., clear, tongued and grooved, hard pine, placed vertically, which did fairly well and lasted to the end (about 1,000 ft.), although it was not altogether satisfactory, and the last eight or ten sections built had to be rubbed down with a wooden float in order to obtain a suitable finish.
In designing the forms for all exposed surfaces in the tunnels, it was the desire of the contractors to obtain directly from them a surface which would be satisfactory to the engineers without further finishing than the patching of minor defects. In this they were generally quite successful, and excellent results were obtained, as shown in the view of the finished tunnel, Fig. 2, Plate XXVII. The surface of the bench-walls was obtained solely by spading the face with a flat spade as the work progressed. No after treatment was resorted to, except for the few sections where the forms became worn. The top of the bench-wall was finished with a float about 2 or 3 hours after the concrete was placed.
When the work was well organized, a bench-wall was built at each end each day, one day in the North Tunnel, and the following day in the South. During the time sand-walls were being built, a sand-wall and bench-wall were built on alternate days in each tunnel, care being taken that when a bench-wall was being built in one tunnel, the sand-wall was being built in the other, this being necessary in order to equalize the work of the night gang and the conduit layers as well as the transportation.
The conduit layers on the day shift, two or three men and a foreman, required about 2 hours in the forenoon and 1 hour in the afternoon to lay their portion of the conduits, and usually finished this work by 3 P.M. At other times during the shift they were utilized at those points where rock packing was heaviest, and when the packing was brought in in the large cars, as shown in Fig. 1, Plate XXVI, these men helped unload it so that the track could be cleared as soon as possible. When water-proofing was to be done, the number of men in this gang was increased, so as to enable them to do that work also.
[Illustration: Plate XXVI. Fig. 1: K 167. P.R.R. Tunnels, N. R. Div. Sect. K. (Bergen Hill Tunnels.) View of form for circuit breaker chamber at Sta. 286, and travelling gantry for placing concrete in arches, looking Easterly from near Sta. 280+85, South Tunnel. Oct. 3, 08. Fig. 2: K 166. P.R.R. Tunnels, N. R. Div. Sect. K. (Bergen Hill Tunnels.) View of forms for storage chamber at Sta. 294+24, looking Southward. Sept. 17, 08. Fig. 3: K 163. P.R.R. Tunnels, N. R. Div. Sect. K. (Bergen Hill Tunnels.) Tunnel lining. Rock packing over arches, South tunnel Sta. ???+?? end of completed section. May 19, 08. Fig. 4: K 168. P.R.R. Tunnels, N. R. Div. Sect. K. (Bergen Hill Tunnels.) Showing method of waterproofing in timbered tunnel section at Weehawken end. Oct. 21, 08.]
A gang of four rough carpenters and a foreman was employed on the day shift; they moved and set the bench-wall forms or sand-wall forms, as the case might be, and moved the traveling gantry into position. This was done in the afternoon, and required about 3 hours. They also took out, cleaned, repaired, and set all ditch forms, all passenger forms, circuit-breaker forms, and did all other repair work. The ladder forms, the refuge-niche forms, and overhead conductor pocket forms were attended to by one man, who set, removed, cleaned, and repaired them. The carpenters on the night shift set the arch centers and gantries, also the manhole forms when needed. The conduit layers on the night shift laid up half the 4-way conduits (3-high) and one-third of the single ducts (4-high). This one gang laid the conduits in two sections of bench-wall each night, that is, one section at Weehawken and the other at the western end.
In concreting the bench-walls, the concrete was first placed on the side containing the single conduit until it reached the top of the four tiers laid, then the concrete gang was turned over to the side with the 4-way conduits while four more tiers of single conduits were laid, the work thus progressing, the conduits being laid on one side while concrete was placed on the other. On the side of the 4-way conduits the concrete was built in two layers while that on the side of the single ducts was built in three; the interval between the different layers was not sufficiently long to prevent a complete bond being obtained, and there were only one or two instances where there was any mark on the face to indicate a break.
After the work had been in progress some time, it was found to be quite feasible to build all the 4-way conduits at night and half the single conduits, that is, 6 ducts high, as the mandrels proved amply sufficient to hold them in place; in fact, had it been necessary, the writer has no doubt that all the ducts might have been laid and held in place with very little extra precaution, by the use of the expanding mandrels, as described under the head of conduit laying. A V-shaped joint about in. deep was made between each section of bench-wall so that the expansion cracks would follow this joint rather than show irregularly on the face. These joints divided the face into the even 25-ft. panels, and were very effectual in concealing what few cracks there were.
After the construction of the sand-walls was discontinued, the space behind the bench-walls, between the neat line and the rock, was filled with rock packing, which was generally built, part way up at least, as a dry wall ahead of the construction of the bench-wall, or it was put in place simultaneously with the concrete, care being taken to keep it as free as possible for the drainage of any water there might be. Toward the latter part of the work, owing to the difficulty of getting sufficient rock packing during the day, a rough back form for the bench-wall was built at the neat line, in places where the section was at all large, and the space was filled with rock afterward, generally at night or on Sundays.
In the sections where water-proofing was required, where no sand-wall was built, the rock was taken out for 2 ft. outside the neat line, if the excavation was not already that far out (at the expense of the contractors, who preferred to do this rather than build the sand-walls for the short sections required), so that there would be sufficient room for placing the water-proofing on the back of the bench-walls, as shown by Fig. 18, E. The water-proofing of these sections was left until just before the arch was to be built, and after being placed it was protected by a single row of brick laid on edge before the rock packing was filled in.
Arches.—The centering used for the arches is shown very clearly in Fig. 4, Plate XXV, which is a view of the back end of the first section built at Weehawken. In this part of the tunnel, the lower part of the arch, about 5 ft. above the bench-wall, was built first, as previously referred to, but the centers, as will be seen, were built so that they could be used for the whole of the arch. The forward bulkhead, and the shoveling platform on a section being built, are shown in Fig. 3, Plate XXVI.
The front bulkheads used were made in nine sections, bolted to a 2 by 2-in. angle bent to the radius of the arch, as shown in Fig. 3, Plate XXVI, and fitting on the end of the lagging; when set they were braced partly against the rock of the roof and partly against the gantry. After the ribs and part of the lagging had been set by the night gang for a fresh section of arch, the braces holding the bulkheads were knocked out, the concrete placed during the day having set sufficiently by this time; the whole of the bulkhead was then easily moved ahead, sliding along the lagging to the forward end, and made ready for the next day's work. The middle section at the top was taken out temporarily, to facilitate working at the sides, until it was needed.
The traveling gantry used in handling the concrete for the arch is shown in Fig. 1, Plate XXVI, which also shows the form for the circuit-breaker chamber, and a car of rock packing on the track beneath.
The arches were built in 10-ft. sections, the ribs being spaced 5 ft. apart, the end ribs of each section supporting the end of the lagging on two adjoining sections. Five sets of lagging and ten ribs were used at each place where the arch was being built, thus giving each section practically 4 days' set before removing the centers. Probably in the greater part of the work the centers could have been removed in from 40 to 48 hours after the concrete had been placed, but 3 days was considered the least time which would certainly be safe at all times, and the contractors thought that the very slight additional expense involved in leaving the centers up 4 days was more than warranted by the additional feeling of security.
The lagging was made from 3 by 6-in. clear, hard pine, 10 ft. long, dressed to about 2 in. in thickness, about 5 in. in width, and the sides to radial lines. As it was placed, every third or fourth piece was lightly nailed to the ribs; when the latter were released and taken down, the nails pulled out, and the lagging was left in place until one piece was pried out, allowing the others to fall. A light A-frame, about 8 ft. long, spanning the bench-walls, was placed below, in order to break the fall and allow the lagging to slide to the top of the bench-walls rather than fall to the track beneath.
Cross-passages between the two tunnels were built every 300 ft., their form being shown on Plate VIII of the paper by Mr. Jacobs. There were two circuit-breaker chambers, one at Station 286 and the other at Station 310. Steel doors are provided so that all the openings between the two tunnels can be closed. At Station 294+24, the core-wall broke through for a length of about 40 ft., and instead of filling this in, a storage chamber 34 ft. long and 11 ft. wide, inside, was built there, the form for which is shown in Fig. 2, Plate XXVI. This photograph, as well as Fig. 1, Plate XXVI, a form for a circuit-breaker chamber, shows the method of setting the steel doors in the forms, so that they were built into the concrete instead of being fastened in with expansion bolts afterward, thus showing a perfect fit and a much neater job.
During construction the arches in each tunnel were kept even with each other, so that when the cross-passages were reached, they, and the sections of arch which they joined, could be completed at one operation.
By the methods used on this work, one section of arch was easily built in a shift, so that the monolithic construction of each section was easily secured, and concrete, as wet as it was possible to handle with shovels, could be used for all except the last 5 ft. or so at the top, thus getting a structure which was as nearly impervious as possible under the circumstances.
The gangs placing the arches were paid over-time when they were required to work after 6 o'clock to finish their section, which was generally only necessary when the quantity of rock packing to be placed was very large. If they finished their section before 6 o'clock, however, they were allowed to quit when this was done, and were given a full day's pay. The difference in time, when there was any, was usually due to the greater or less quantity of rock packing, as the excavation varied from the standard section line.
In building the arches, the night gang set the two ribs (one at the center and one at the forward end of the section to be built), placed the lagging on the sides, 4 or 5 ft. high, built the shoveling platform on the horizontal cross-braces of the ribs, and placed the traveling gantry in position for use. The forward end of the gantry (that is, the end farthest from the arch being built), as shown in Fig. 1, Plate XXVI, was loaded with rock packing to be used as required. As the concrete was brought into the tunnel it was hoisted and dumped on the end of the gantry next the arch, and shoveled from there to the platform on the ribs and from there into place. The rock packing brought in during the day was dumped on the front or back end of the gantry, as was most convenient, and handled into the work in the intervals between batches of concrete. The concrete and rock packing, with the back-lagging and water-proofing, where these were used, were placed simultaneously, or nearly so, and brought up the sides together until the key was reached; the latter was then worked from the back toward the front. The key was usually made about 5 ft. wide, the lagging for this width was made 5 ft. long and put up in two sections. It was found to be more convenient to have the key of this width than narrower.
The method used in making the closures where two sections of the arch came together is shown by Fig. 17.
SKETCH SHOWING METHOD OF MAKING ARCH CLOSURE CROSS-SECTION OF TUNNEL SHOWING JACK PARTLY EXTENDED LONGITUDINAL SECTION OF TUNNEL SHOWING JACK PARTLY EXTENDED PLAN OF BOX; END VIEW PLAN OF PLUNGER, BOTTOM OF BOX; END VIEW OF PLUNGER, JACK FULLY EXTENDED]
Water-proofing.—As already pointed out, the original design for the lining of these tunnels provided for a brick arch. It was intended to cover this arch with water-proofing, this latter extending over the whole of the roof and down the sides as far as the bottom of the conduit lines. The water-proofing was to be placed against the sand-walls on the sides, up to the top of the side walls, Figs. 10 and 14. Over the arch, after being placed, it was to be protected by an armor course of brick, laid flat, the space between the brick and the excavation, which was required to be not less than 4 in. (and, as a matter of fact, was actually a great deal more), being filled with rock packing. Besides filling the space, this latter was designed to allow any water from the roof of the tunnel to find its way easily to the top of the sand-wall, from there being carried through the 4-in. cast-iron pipes, shown on Plate VIII to the side ditches in the floor of the tunnel.
[Footnote 4: Of the paper by Mr. Jacobs.]
All the water-proofing placed in these tunnels was of felt and pitch, six-ply felt and seven layers of pitch. The felt was required to be Hydrex, or of equal quality, and the pitch, "Straight run coal-tar pitch which will soften at 60 Fahr., of a grade in which the distillate oils will have a specific gravity of 1.05."
In addition to tests as to the above qualities, the pitch was analyzed to determine the amount of free carbon it contained, and was not accepted if this fell below 20 per cent.
It was considered quite important that there should be absolutely free drainage on the outer side of the lining, so that there would be no chance for any water to acquire a head. More than three-quarters of the length of these tunnels is below the level of mean high water, and while it was hardly expected that there would be any direct connection between the water in the Hudson River and the groundwater of the section penetrated, it was thought wise to provide ample drainage.
Before the lining was started, however, the excavation had progressed sufficiently to show that the tunnels, while very wet in places, and varying from that to quite damp, would be, on the whole, much dryer than had been anticipated. It was then decided to substitute concrete for the brick in the arch and omit the water-proofing over the top, except at places where water came into the tunnels in sufficiently large quantities to form practically a continuous stream. Three general types of construction for the arch were decided on, as shown in Fig. 18. The first, as shown at A, was to be used where the tunnel was quite dry. In this type, the sand-wall was omitted entirely, and the concrete and rock packing were built up together, the rock packing impinging to a certain extent on the concrete, and the concrete squeezing somewhat into the rock packing, as shown by Fig. 4, Plate XXV. The section shown at B was used where the tunnels were damp, or where there were slight droppers not forming a continuous stream. The back lagging, of 1-in. boards, which was left in place, provided a practically smooth outer surface on the concrete arch, and allowing the concrete and rock packing to be built almost simultaneously. It was considered that the free drainage through the rock packing, the surface of the boards, and the smooth outer surface of the concrete in the arch would allow the comparatively small quantity of water in these parts of the tunnel to find its way to the sides, and thence to the ditches at the bottom, rather than to percolate through the concrete, and this proved to be very generally the case, as is shown by the dry condition of the tunnel as built. The back lagging was used over the arch, both where the sand-wall was built and where it was omitted, as well as being placed over the water-proofing of the arch as an armor course where water-proofing was required. Where the sand-walls were built and water-proofed, and where the water-proofing was not carried over the arch, the water-proofing was turned in at the top, as shown at C, Fig. 18.
VARIOUS TYPES OF ARCHES, AND WATER-PROOFING USED Method of Lapping Mats over Arch Method of making joint when work on section was not continuous. Part of joint on radial line, part sloping slightly toward outside of arch. DETAILS OF WATER-PROOFING One layer of felt with 4" overlap to be nailed to lagging of inch boards, using tin washers on nails over the whole of the intrados of the arch before starting any concrete or placing any of the permanent felt and pitch water-proofing. The water-proofing over the arch can be laid in mats of three thicknesses of felt properly joined together with pitch made as shown diagrammatically at "x" Each of these mats of three-ply felt will be overlapped half the width of the mat, as shown diagrammatically at "y"]
The third method provided for water-proofing the whole of the arch, and was the same as B except for the addition of the water-proofing inside the back lagging. In placing this water-proofing, the felt was cut in strips about 11 ft. long (about 1 ft. longer than the length of a section of arch), and six thicknesses were cemented together with hot pitch. These mats were then laid shingle-fashion, as shown at D, Fig. 18, up the sides of the arch until a space about 5 ft. wide remained at the crown; shorter mats were then brought out over this, laying them perpendicular to the axis of the tunnel. Care was taken in making all laps, irrespective of the direction in which the arch was built, so that they would lay with the grade, that is, so that the water would tend to flow over the edges of the laps rather than against them.
Most of the wet sections of the tunnel were at the ends, where sand-walls had been built for the purpose of providing a smooth surface against which the water-proofing was to be placed; there were several wet places at isolated points in the tunnels, however, and, in order to avoid building sand-walls at these points, the method shown at E, Fig. 18, was adopted. This involved a slightly larger excavation, 2 ft. outside of the neat line, up to the height of the top of the bench, where there was not already that much room. The bench-wall was built with a back form on the neat line, the water-proofing was placed as shown, protected by an armor course of brick, and then continued over the arch when this latter was built. The excavation and refilling with rock packing were done at the contractor's expense, which he was willing to assume rather than build these short sections of sand-wall.
[Illustration: Plate XXVII. Fig. 1: K 181. P.R.R. Tunnels, N. R. Div. Sect. K. (Bergen Hill Tunnels.) Timbered section near Weehawken Shaft, showing method of placing waterproofing and keying arch. Dec. 8, 08. Fig. 2: K 184. P.R.R. Tunnels, N. R. Div. Sect. K. (Bergen Hill Tunnels). View of completed tunnel looking Eastward from Sta. 323+60. South Tunnel. Feb. 8, 09. Fig. 3: K 149. P.R.R. Tunnels, N. R. Div. Sect. K. (Bergen Hill Tunnels) Hackensack Portal, general view of completed Portal, and arches through cut and cover section looking East. Oct. 15, 07. Fig. 4: K 190. P.R.R. Tunnels, N. R. Div. Sect. K. (Bergen Hill Tunnels.) Hackensack Approach. General view, looking East. March 16, 09.]
The method of water-proofing that part of the timbered section which was very wet, is shown at F, Fig. 18, and in Fig. 4, Plate XXVI, and Fig. 1, Plate XXVII. A lagging of 1-in. boards was nailed up the sides and to the soffit of the segmental timbering, all the spaces outside of this lagging being carefully filled with rock packing. Before starting any concrete work, a single thickness of water-proofing felt was nailed to the inner side of the lagging, which not only served to protect the finished surfaces of the concrete from the water which fell copiously from the roof, but also provided a comparatively dry surface to which the regular six-ply water-proofing could be cemented with pitch and held in position, while the concrete was placed against it.
In placing the water-proofing in this section on the sides, the strips of felt were placed vertically, nailed at the top to the wall-plate, to support their weight, and lapped and cemented with pitch to the sides as on the sand-walls, except that there was no trouble from the overhang. After the bench-wall had been built, the felt was cut just below the nails and about 2 ft. above the top of the bench, so that the mats which were placed over the arch could be inserted behind it. The roof was covered with three-ply mats and lapped over a little more than half, as shown diagrammatically on the drawing.
When the upper part of the arch was reached, where the cementing strength of the pitch was not sufficient to hold the felt in place, the mats were braced temporarily from the centering, as shown by Fig. 1, Plate XXVII, until the concrete could be packed against it.
Where the water-proofing was placed against the sand-wall, the method of securing the sheets at the top is shown in the small sketch on Fig. 14 and by Figs. 3 and 4, Plate XXIV. Fig. 3, Plate XXV, shows the laps of the sheets and the method of hanging. At the start an attempt was made to stick the water-proofing to the sand-wall, but this could not be done on account of its dampness and the overhang at the top.
The sand-wall water-proofing was kept about 35 ft. ahead of the finished bench-wall, as shown by Fig. 3, Plate XXV. As the bench-wall form was moved ahead and set, the mat was braced back against the sand-wall from the forms at a point just above the top of the finished bench, care being taken to avoid wrinkles, as, if these were once formed, it was practically impossible to straighten them out.
The completion of the bench-wall left the upper part of this water-proofing stretched taut across the curved top of the sand-wall, forming a chord of the arc. As the arch was built up, the top was gradually slackened so as to allow the concrete to press the mat back into place until the top of the sand-wall was reached, when the end was turned in, as shown at C, Fig. 18, or the water-proofing was continued over the arch, if that was necessary.
The desire to obtain a dry tunnel, and the methods adopted to secure it, were responsible in a great measure for the decision to build the arch in short lengths, as well as the reasons given under the head of arches. Had the tunnels been dry throughout, the method shown at A, Fig. 18, could have been used exclusively, and, except for the fact that monolithic concrete might not have been obtained, there would have been no objection to building longer lengths.
The quantity of water reaching the tunnel drains and flowing out of their lower ends after the completion of the lining was about 100,000 gal. per day, or 75 gal. per min.; of this it is estimated that considerably less than 1% comes through the lining in the form of leaks. The very general distribution of this water over the roof is indicated by the fact that, during the excavation of the first 1,000 ft. of both tunnels from the Weehawken end, oilskins had to be provided for the laborers to induce them to work at all. The success, therefore, of the rock packing as a means of diverting this water to the side drains, is shown, especially in view of the fact that, excluding the cut-and-cover section, only 10% of the length of the arch, 1,189 ft., was water-proofed.
Considerable care was taken to make all joints in the concrete which were in such a position that water might follow through them to the inside of the tunnel lining, in such a manner that they would slope outward toward the rock. The top of the sand-wall is shown by Figs. 14 and 18. The slope of the back of the foundation may be noted in Fig. 18, and the method of making the joint in the arch, in the few instances where a section was not completed at one operation, is shown at A, Fig. 18. These joints in the arch were not allowed to be made above a point 60 above the springing line.
HACKENSACK PORTAL AND APPROACH.
The approach cut at the western end is 300 ft. long, the alignment being a 2 curve, as shown in Fig. 19. The bench-walls and conduit lines built throughout the length of the tunnels are extended through the approach cut, the top of the former gradually sloping from the portal to the mouth of the cut, where they are just level with the top of the rail, the conduits also being depressed to the same relative position with the tops of the benches.
BERGEN HILLS TUNNELS. Hackensack Portal and Approach. SECTIONS AND ELEVATIONS. PLAN OF APPROACH. PROFILE THROUGH APPROACH. SECTION SHOWING METHOD OF MAKING JOINT BETWEEN COPING AND WALL. PLAN SHOWING METHOD OF MAKING JOINT BETWEEN ADJOINING SECTIONS. SECTION OF BENCH AND RETAINING WALLS AND HALF ELEVATION OF PORTAL.]
The top of the rock at the mouth of the cut, Station 327, was from 4 to 6 ft. below the top of the rail, and gradually rose through the approach until at the portal it was about 6 or 8 ft. above the roof of the tunnel. The rock was covered with hardpan. A profile of this part of the work is shown on Fig. 19. The rock throughout the approach was water-bearing to a considerable extent, and a face-wall was built at the sides with free drainage, through rock packing and vitrified and cast-iron drains behind it, to keep this water from flowing over the tops of the bench-walls, and also to keep the lines of conduits dry.
The retaining walls were built in 25-ft. sections, the joints corresponding to those in the benches, being at the even stations, +08, +33, +58, and +83. V-shaped joints were made down the face, and the ends of the sections were made as shown by Fig. 19. The back part of the joint was mopped with hot pitch before the next section was built, so that there was practically no bond between any two adjoining sections.
The concrete in these walls was placed late in the season, and the expansion cracks, which were entirely confined to the V-shaped joints, were quite small even in the coldest weather of the following winter, nor were there any indications during the past summer of any stresses due to expansion. The coping and drain at the top of the wall were built together, but separate from the rest of the wall, the joint being made as shown in the sketch on Fig. 19. Thus far, there has seemed to be no seepage through either the vertical or horizontal joints.
The portal is built of granite, a half elevation being shown on Fig. 19, the stone being supplied by the Millstone Granite Company, Millstone Point, Conn. Fig. 3, Plate XXVII, shows the portal and the cut-and-cover section after the arches were completed but not covered.
The forms for the concrete in the approach were made of ordinary dressed lumber, and the surface was rubbed twice after the forms were removed, which was as soon as possible after the concrete had set. The surface was first very lightly rubbed with a piece of soft, light-colored, sandstone to remove any irregularities, being wetted slightly if necessary while being rubbed. After the concrete had become fairly hard and dry, it was rubbed a second time and a uniform texture and color obtained. The completion of this work was delayed until the second week in January, and considerable difficulty was encountered in obtaining a good finish of that part which was built after cold weather set in, when it was necessary to protect it from frost. Unless extreme care was taken to prevent freezing after the rubbing, the entire surface was likely to scale off, although no cement or other material was added to it after the removal of the forms. A general view of the completed approach is shown by Fig. 4, Plate XXVII.
- -+ DAY. NIGHT. Title. + - - - - - No. Rate. Amount. No. Rate. Amount. - - - - - -+ Walking bosses 2 $5.00 $10.00 Timekeeper 2 3.00 6.00 Watchmen 5 $2.00 $10.00 Waterboys 1 1.50 1.50 Carpenter foremen 2 3.50 7.00 1 4.00 4.00 Carpenters 14 2.50 35.00 8 2.50 20.00 Pipe-fitters 1 3.00 3.00 Pipe-fitter's helper 1 1.75 1.75 Wheelwright 1 2.75 2.75 Wheelwright's helper 1 1.75 1.75 Blacksmith 1 3.00 3.00 Blacksmith's helper 1 1.75 1.75 Foremen riggers 1 3.00 3.00 Riggers 6 1.75 10.50 Foremen trackmen 1 3.00 3.00 Trackmen 6 1.50 9.00 Machinist 2 3.00 6.00 Machinist's helper 1 1.75 1.75 Electrician 2 3.00 6.00 1 2.50 2.50 Electrician's helper 1 1.75 1.75 Lampman 1 1.50 1.50 Pumpman 1 1.50 1.50 Finishers 3 2.50 7.50 Hoist engineers 12 3.00 36.00 Dinky engineers 5 2.75 13.75 1 2.75 2.75 Brakemen 5 1.75 8.75 1 1.75 1.75 Switchmen 1 1.50 1.50 Barnmen 1 2.00 2.00 1 2.50 2.50 Drivers 9 1.50 13.50 Foremen ductmen 2 2.50 2.50 Ductmen 5 2.00 10.00 Foremen laborers 13 3.50 45.50 2 3.50 7.00 Laborers 120 1.75 210.00 20 1.75 35.00 Compressor engineer 1 3.50 3.50 1 3.50 3.50 Firemen 2 2.50 5.00 1 2.50 2.50 Oiler 1 1.75 1.75 Coal passers 2 1.75 3.50 1 1.75 1.75 -+ - - - - - Totals 334 $469.75 50 $108.25
Total daily labor expense $578.00 ——————————————————————————————————-
The water finding its way into the side ditches in the approach, which of course included all rain falling in this area, was intercepted just inside the portal and carried back to the mouth of the cut through 24-in. cast-iron pipes laid beneath the conduits in the central bench-wall, thus disposing by natural drainage of a not inconsiderable quantity of water which would otherwise have flowed through the tunnels to the sump at the Weehawken Shaft, from which it would have had to be pumped to the surface.
About 100 ft. of the tunnel immediately east of the Hackensack Portal was built by the cut-and-cover method, and the arch section used in the tunnel was modified by widening the haunches, the thickness of the arch at the crown being gradually increased from 22 in. at the portal, Station 324, to 34 in. at Station 323, where the regular segmental timbering at the tunnel commenced. A general view of the approach during construction is shown by Fig. 1, Plate XXV.
Table 6 shows approximately the number of men employed daily on the tunnel lining, by both the contractor and the sub-contractors, their occupation, the average rate of wages and the total daily expense for labor when the work was in full swing.
The whole of the work of the North River Division was designed and executed under the direction of Charles M. Jacobs, M. Am. Soc. C. E., Chief Engineer, and James Forgie, M. Am. Soc. C. E., Chief Assistant Engineer, the construction of Section "K," Bergen Hill Tunnels, being directly in charge of the writer as Resident Engineer.
[Transcriber's Note: The two organizational charts, Figs. 20 and 21, have been reformatted for space.]
[Chart: Fig. 20.
PENNSYLVANIA TUNNEL AND TERMINAL RAILROAD COMPANY, SECTION "K"—BERGEN HILL TUNNELS.
Organization of Staff of Resident Engineer.
Organization Previous to the Holing Through of the Tunnels.
Resident Engineer. ___ __ Assistant Assistant Engineer. Engineer. __ __ Cost and Office Field Inspection. Alignment. Records.
Cost and Office Records. Inspector. Two Clerks. Stenographer. Telephone Operator. Messenger. Janitors.
Field Inspection. Weehawken. Chief Inspector. Inspector, N. Tunnel " S. Tunnel. " Mixer. " Excavation and Force Account. Inspector, Night. Cement Warehouseman. Conduit Inspector. (one position) Hackensack. Chief Inspector. Chief Inspector. Inspector, N. Tunnel " S. Tunnel. " Mixer. " Excavation and Force Account. Inspector, Night. Cement Warehouseman. Conduit Inspector. (one position)
Alignment. Weehawken. Chief of Party. Instrumentman. Rodman. Chainman. Hackensack. Chief of Party. Instrumentman. Rodman. Chainman.]
[Chart: Fig. 21.
Organization After the Tunnels Had Been Holed Through.
Resident Engineer. Assistant Assistant Engineer. Engineer. Cost and Office Field Inspection. Alignment. Records. Tunnels. Conduit Inspector.
Cost and Office Records. Two Inspectors. Two Clerks. Stenographer. Telephone Operator. Messenger. Janitor.
Tunnels. Chief Inspector. 8 Tunnel Inspectors. 2 Mixer Inspectors. 1 Night Inspector. Conduit Inspector. Inspector, Hackensack Approach.
Alignment. 1 Instrumentman. 1 Draftsman. 2 Rodmen. 3 Chainmen.]
The general organization of the staff is shown by the two diagrams, Figs. 20 and 21. Fig. 20 shows the organization previous to the holing through of the tunnels, during which time a separate office was maintained at the western end for the use of the men stationed there; Fig. 21 shows the organization during the latter part of the time, after the tunnels were holed through. The Assistant Engineer in charge of the construction was J. R. Taft, Assoc. M. Am. Soc. C. E.; the Chief Inspector, J. S. Frazer, Jun. Am. Soc. C. E., had charge of about 75% of the work of the lining of the tunnels. The alignment has been from the beginning under the charge of R. L. Reynolds, Assistant Engineer.
* * * * * * * * * * * * * *
Errors and Notes:
Each Plate was printed with the same header: PLATE _. TRANS. AM. SOC. CIV. ENGRS. VOL. LXVIII, No. 1154. LAVIS ON PENNSYLVANIA R.R. TUNNELS: BERGEN HILL TUNNELS. These headers were omitted for the e-text. Captions beginning in "K" with a number were printed directly on the photograph; some readings are uncertain and are indicated by question marks (?).
In the tables of Figures 1-4, variation between "to" and "-", and formatting of table entries, is as in the original.
[Fig. 1, table] Per cubic yard, whole tunnel section: 3-33 may be error for "3-3.3" [Fig. 1, last line of table] Total Pounds text reads "Pound" Figs. 3 and 4, and Plate XXIV apparent error for "Figs. 3 and 4, Plate XXIV" (usual form) [Figure 15 A, B, C...] letters other than "B" do not appear in the printed Figure [Figure 15, caption] DETAILS OF "WEASEL" quotation marks look hand-written, but printed text has spaces [Figure 15, "Index" (small table)] Multi-Duct Mandrel text reads "Mult-Duct" which would be satisfactory to the engineers text reads "satifactory"
Missing or superfluous punctuation was silently corrected.