CHAPTER XVI.

METHODS AND COST OF LINING TUNNELS AND SUBWAYS. [Illustration: Fig. 126.--Section Showing Lining for Capitol Hill Tunnel. Washington, D. C.] Tunnel lining work is of two distinct classes: Lining work, done during original construction and relining of tunnels in service. The methods of work to be adopted and the cost of work will be different in the two cases. In relining work the costs are increased by the necessity of providing for the movement of trains and by the delays due to these movements and also by the labor of removing the old lining and, often, of enlarging the excavation. Comparatively few published figures are available on the cost of concrete tunnel lining, and such as exist are commonly incomplete. The common practice is to record the cost as so much per lineal foot of tunnel. This should be done, but the record should also show the cost per cubic yard of concrete in the lining. The notions of engineers vary as to the proper thickness of lining to use and this dimension also varies with the character of the ground. One tunnel lining may easily contain twice as many cubic yards of concrete per lineal foot of lining as another tunnel contains. The two problems in form construction for tunnel work are: First, to construct the form work so that it does not interfere with train movements, and, second, to construct it so that it can be taken down, transported and re-erected and thus used over and over. The examples of practice given in the succeeding sections are the best instructions that can be laid before the reader in regard to possible ways of solving these problems and, also, the problem of handling the concrete and other materials to the work. [Illustration: Fig. 127.--Traveling Derrick for Constructing Side and Center Walls, Capitol Hill Tunnel.] [Illustration: Fig. 128.--Steel Forms for Side Walls for Capitol Hill Tunnel.] ~METHOD OF LINING CAPITOL HILL TUNNEL, PENNSYLVANIA R. R., WASHINGTON, D. C.~--The tunnel through Capitol Hill for the Pennsylvania R. R. approach to its new Union Station at Washington, D. C, is a two-track, double tube tunnel 4,000 ft. long through earth. Figure 126 shows the lining construction; it consists of stone masonry center wall, mass concrete inverts and side walls and a brick roof arch backed with concrete. For building the center and side walls the traveling derrick shown by Fig. 127 was employed. This traveler moved ahead with the work on a 14-ft. gage track and it handled the stone and concrete buckets from the material cars to the workmen on the walls. In connection with the derrick in the concrete side wall construction use was made of steel plate forms for the inside faces of the walls. These forms were made of 4×10 ft. sections of steel plate, constructed as shown by Fig. 128, and connected together by bolting through the flanges. The steel forms were erected by hand in advance of the derrick, 20 ft. of form on each side at a time. The concrete buckets were brought into the tunnel on cars hauled by electric motors from the mixing plant at the portal, and the buckets were lifted by the derricks and emptied into the forms. The side walls were concreted to the springing line and then the five-ring brick roof arches were constructed on traveling centers and in 20-ft. sections. The remainder of the concrete was then placed over the arches by means of the special back-filling machine, shown by Fig. 129. This machine also handled the earth used to fill behind the masonry. It consisted of a platform mounted on wheels and of the same general construction as the derrick platform. On the forward end of this platform a stationary hoist was mounted and behind this a belt conveyor platform. [Illustration: Fig. 129.--Device for Placing Concrete Back Filling for Roof Arch, Capitol Hill Tunnel.] The latter structure was pivoted near the forward end so that it could swing right and left on a circular track under its rear end. It carried a 30-cu. ft. hopper on its forward end, from under which a belt conveyor ascended an incline toward the rear and was carried back into the space behind the roof arch on a cantilever arm. In operating the back-filling machine the material bucket was lifted from the car below, carried back on the trolley beam until over the hopper and then dumped by hand into the hopper. From the hopper the material dropped onto the conveyor belt and was carried back over the arch and dumped in place ready for tamping. The trolley beam of the hoist was so arranged that the hoisting movement was vertical until the bucket hit the trolley and was then up and backward until the stop at the end of the trolley beam was reached. This point was directly over the hopper. Hoisting was done by a Lambert engine, driven by a 15 H.P. electric motor. The conveyor belt was 20 ins. wide and was operated at a speed of 180 ft. per minute by a 7½ H.P. electric motor. The machine required two men to operate and was considered to save the labor of twelve shovelers. ~METHOD OF CONSTRUCTING SIDE WALLS IN RELINING THE MULLAN TUNNEL.~--The Mullan Tunnel, 3,850 ft. long, on the Northern Pacific Ry., about 20 miles west of Helena, Mont., had its original timber lining replaced in 1894 with a lining consisting of concrete side walls and a brick roof arch. The construction of the old and new linings is shown by Fig. 130. The method of constructing the side walls was as follows: The original timbering consisted of sets of 12×12-in. posts carrying five segment arches of 12×12-in. timbers joined by ½-in. dowels. For a portion of the lining the posts carried plates on which the arches set; elsewhere the arches rested directly on the post tops. The arches and posts carried 4-in. lagging filled behind with cordwood. The timber lining was removed to make place for the new work in the manner shown by Fig. 130. When there were no plates a 7-ft. section AB was first prepared by removing one post and supporting the undermined arch ribs by struts SS. The timbering in this section was cut out and excavation made for the wall footing. Two temporary posts FF were then set up, fastened by hook bolts L and lagged behind to make the wall form. Several of these 7-ft. sections were cut out at once, each two being separated by a 5-ft. section of timbering. The mortar car shown in Fig. 130 was then run alongside the sections in order and enough 1-3 mortar was run by chute into each to make an 8-in. layer. As the car moved ahead to succeeding sections enough broken stone was shoveled into the last preceding section to take up the mortar. The walls were thus built in 8-in. layers and became hard enough to support the arches in from 10 to 14 days. The arches were then allowed to take footing on the wall, and the posts of the remaining 5-ft. sections were removed and the concrete wall built up as for the 7-ft. sections. Where the posts carried wall plates the struts SS were not needed, the wall plate supporting the undermined post as a beam. English Portland cement was used and the concrete mixture was about 4 parts mortar to 5 parts broken stone--a very rich mixture. The average progress was about 30 ft., or 45 cu. yds. of side wall per working day; the average cost of the walls, including everything, was $8 per cu. yd. of concrete. The brick arch cost $17 per cu. yd. Mr. H. C. Relf is authority for these figures. [Illustration: Fig. 130.--Sketches Showing Method of Lining Mullan Tunnel.] ~METHOD AND COST OF LINING A SHORT TUNNEL, PEEKSKILL, N. Y.~--The following methods and costs of lining a double track railway tunnel 275 ft. long near Peekskill, N.Y., are given by Mr. Geo. W. Lee. In presenting these data it is important to note that while some of the methods described are applicable to so short a tunnel they could not be used on a long tunnel. Figure 131 is a cross-section of the tunnel showing the lining. The tunnel was through rock, which stood up without timbering, and the rock section was excavated from 6 ins. to 3 ft. outside the lining. A 1-2-4 concrete using crusher run stone below 1 in. in size was used for the lining and portal head wall coping and a 1-3-6 concrete for the portal head walls proper. The cost of the portal head walls is included in the costs given further on. [Illustration: Fig. 131.--Cross-Section of Peekskill Tunnel, Showing Lining.] The side wall foundation trenches were first excavated from 1 to 3 ft. deep and footing concreted and leveled up, the back of the footing being carried up against the rock and the front lined to forms giving a 12-in. offset to the side wall. The footings contained 200 cu. yds. of concrete. Platforms 25 ft. square and level with the springing lines were then erected at each end of the tunnel. A derrick was placed at each platform to handle skips between it and the material tracks which ran underneath and through the tunnel with a turnout at each end for switching back empty cars. A 60 H.P. portable boiler supplied steam for the derrick engines and a pump. The wall forms were built and erected in panels 12 ft. long; these panels had 4×6-in. plates and sills, 4×4-in. studs 3 ft. on centers and 2-in. dressed and matched spruce sheeting. Four panels were set up, two on each side, midway of the tunnel and braced to the tunnel track. Wheelbarrow runways carried on bents were built from the platforms to the forms, one from one platform to one side, another from the other platform to the opposite side. Temporary bulkheads were erected to close the ends of the forms and they were filled. Meanwhile carpenters were setting other panels at each end of the two first erected on each side. After 24 hours the panels first set were taken down and moved ahead and the processes described continued until the full length of side wall was completed. The side walls were not concreted back to the rock; back forms of 1-in. hemlock were used and the space remaining was filled with spalls. The side walls contained 692 cu. yds. of concrete. Arch forms were erected for 96 ft. at the center of the tunnel, using 12-ft. lagging, so that sections of this length could be taken down and moved ahead, nine at each end. The lagging was first laid to a height of 3 ft. above the springing line on each side and the concrete dumped directly in place from runways laid on the lower chords of the arch ribs, which were placed 4 ft. apart. When the concrete reached a height too great for direct discharge into the forms it was dumped on the runway and passed over with shovels. On the upper portion of the ring the concrete was first shoveled to a platform erected on the center posts of the ribs about 2 ft. below the crown and then passed in on the lagging which was laid in 4-ft. instead of 12-ft. lengths at this stage of the work. As soon as each section of arch ring was completed it was waterproofed with six layers of tar paper laid in hot tar and then packed behind with spalls. The arch centers were struck in a comparatively short time; in one instance they were struck 90 hours after the last concrete was placed and no settlement was apparent. The arch forms stuck so fast to the concrete, however, that they had to be jacked down by chiseling out the lagging so as to get a bearing on the arch concrete and by nailing thrust blocks to the rib posts. The section was then hauled ahead by passing the main fall of the derrick through a snatch block on the first rib. When hauled clear of the lining all but the first 3-ft. of lagging on each side was removed; they were then jacked into position. The arch ring contained 932 cu. yds. of concrete. Including the portal head walls 1,948 cu. yds. of concrete were laid at the following costs for labor and materials: Item. Total. Per cu. yd. Cement at $1.63 per bbl. $ 5,755.50 $2.951 Sand at $0.75 per cu. yd. 662.94 0.339 Stone at $0.80 per cu. yd. 1,303.20 0.668 Lumber-- Mixing platforms and runways 336.89 0.174 Ribs, including hand sawing 234.10 0.120 Backing boards 134.44 0.069 Lagging 341.04 0.176 Sheathing 268.49 0.137 Plates, sills, studs, braces 182.75 0.093 Coal 118.73 0.061 Oil 16.12 0.008 Hardware, nails, spikes, etc. 224.39 0.118 Tools 181.10 0.093 Freight on stone, cement, etc. 3,089.86 1.584 Labor of all kinds 8,036.31 4.121 ---------- ------- Total $20,885.86 $10.712 ~METHOD OF LINING CASCADE TUNNEL, GREAT NORTHERN RY.~--The Cascade Tunnel, 13,813 ft. long, built in 1897-1900, was lined throughout with concrete from 24 ins. to 3½ ft. thick, mixed and placed in the following manner: It was necessary to place the lining without interfering with the transportation of materials and excavated material to and from the work ahead. The arrangement adopted to secure this end is shown by Fig. 132. A platform 500 ft. long was constructed at the elevation of the wall plates; the rear end of this platform was reached by an incline, up which the cars loaded with concrete were hauled by an air hoist and cable and delivered to any point on this platform. While each 500 ft. of tunnel was being concreted, the next 500 ft. of platform in advance was being built, with its approach incline, so that there was no delay in the work. Complete concrete plants were installed at each portal, advantage being taken of the side hills of the approach into the mountain to handle as much material as possible by gravity. Each plant was equipped with a No. 6 Gates crusher, 40-in.×8-ft. rock screens, and 16-in.×16-ft. screw concrete mixers. Large storage bins for the cement, sand and stone were built adjacent to the mixer plant. A 1-3-5 concrete was used. The stone was crushed from the best rock obtained in the tunnel excavation. This rock was loaded into the regular muck cars, taken to the portal by electric motors, and then dumped into other cars below the level of the muck cars. These cars were hauled by hoisting engine and cable to the crusher floor and then dumped and sorted to avoid danger from pieces of unexploded dynamite. It was then run through the crushers, washers and screens to the stone bin and thence to the mixers. The mixed concrete was discharged into cars on the level of the muck car tracks and these cars were taken by motor into the tunnel to the incline, up which they were hauled by cable and dumped on the platform. From the platform the concrete was shoveled into the wall forms or onto the centers as desired. [Illustration: Fig. 132.--Traveling Platform Used in Lining Cascade Tunnel.] The walls were concreted in alternate 12-ft. sections, the weight on the timber arch thus being gradually transferred from the plumb posts to the walls. The roof arch was also built in 12-ft. sections, the centers being in sections of corresponding length which were moved forward on dollies and jacked up as the work advanced. Ten sections of centering were used at each end. An average of 7 bbls. of cement were used per lineal foot of lining. The average monthly progress of lining was about 600 ft. at each end. The concrete lining cost $44 per lin. ft. of tunnel, done by company forces. ~METHOD OF RELINING HODGES PASS TUNNEL, OREGON SHORT LINE RY.~--The centers and side wall forms and the methods of work adopted in relining the Hodges Pass tunnel on the Oregon Short Line Ry. are explained in the accompanying illustrations. This tunnel is 1,425.8 ft. long and when constructed in 1882 was lined with timber. The new lining consists of concrete side walls carrying a brick roof arch. Both the old and the new linings are shown in the drawings. The tunnel is through a variety of rock and clay strata, and through the soft strata an invert was required. Altogether about one-third of the length of the tunnel was provided with an invert. It will be noted also that the new lining occupies materially more space than the old; this made necessary considerable excavation in enlarging the section. [Illustration: Fig. 133.--Method of Placing Invert Concrete, Hodges' Pass Tunnel.] The work of relining consisted of three operations, viz., the invert construction, the construction of the side walls and the arch construction. [Illustration: Fig. 134.--Method of Constructing Concrete Side Walls, Hodges' Pass Tunnel.] The form of the invert is shown in Fig. 136. It, of course, had to be constructed without entailing a break in the track, and the method adopted was as follows: The ties and ballast were removed from a section of track about 12 ft. long and in their place was substituted the timber frame shown in Fig. 133. Under the middle portion of this frame a trench reaching clear across the tunnel and having a width of 6 to 7 ft. in the direction of the track was excavated to sub-grade of the invert. The concrete was filled into this trench, formed to shape on top, and allowed to harden. The bridging frame was then taken out and the ties and ballast were replaced. Another section of track was then bridged, trenched and concreted and so on until the length of invert required was constructed. [Illustration: Fig. 135.--Side Wall Forms for Plans A and B, Fig. 134.] The side wall construction was a more complex operation. It comprised first the removal of the old lining, the enlarging excavation and the form erection and concreting. Two methods of performing this task were employed. Both are illustrated in Fig. 134. By the first method, designated as Plan A, the concreting was done continuously in sections of considerable length. The forms used are shown in detail by Fig. 135. By the second method, the concreting was done in alternate short panels. This method is designated Plan B on the drawings, Fig. 134. The forms used are shown in detail by Fig. 135. The only difference in the form construction for the two plans is in the connection of the posts at the top. [Illustration: Fig. 136.--General Plan of Centers for Roof Arch, Hodges' Pass Tunnel.] The construction of the centering for the roof arch is shown by Figs. 136 and 137, Fig. 137 giving detail dimensions of the ribs and lagging. The center, as shown by Fig. 136, consisted of four ribs spaced 3 ft. on centers. Each rib consists of two side posts and an arch piece. The side posts on each side are connected at the bottoms by a sill and at the top by a cap. Jacks between the sill and a mud sill laid on the concrete invert or in the ditch held the center in place during arch construction. Lowering these jacks dropped the center onto trucks traveling on the mud sills. Thus the center was moved along as the work progressed. As will be noted from Figs. 134 and 135, the side wall forms carried the work only to the bottoms of the old caps. The arch center completed the concrete wall work and the roof arch. Only about one-third of the new lining had the brick arch, as shown by the drawings; in the remaining two-thirds the concrete was carried up much further on each side; in fact, the brickwork constituted only the top third of the arch. [Illustration: Fig. 137.--Details of Centers for Roof Arch, Hodges' Pass Tunnel.] In describing the forms and centers we have left much of the explanation to the drawings. These show all dimensions and details, and indicate in a measure the mode of procedure. The work done consisted of excavation enlarging the section, of removing the old timber lining and of the form work, concreting and bricklaying for the new lining. All of it above convenient reach from the ground was done from a movable staging formed by a deck fixed on a flat car so as to be adjustable in height. The concrete was mixed by hand on this car platform and shoveled directly into the forms, the platform being raised as the work increased in height. The concrete used was a 1-3-5 mixture of 2½-in. broken stone. The organization of the working force is not easily stated since the work was done as the traffic permitted and varied with the conditions. Generally from 12 to 16 men were all that could be employed to advantage. Complete records of cost were kept, but they were destroyed by fire, so that the only figures available on this point are the totals. These are as follows: Item. Totals. Per lin. ft. Labor $21,129 $14.81 Materials 13,939 9.77 ------- ------- Total $35,068 $24.58 These amounts average the cost of the invert, which was required for about one-third of the length, over the whole tunnel. ~RELINING A SHORT TUNNEL.~--The following figures show the cost of relining with concrete a timber lined railway tunnel. The concrete side walls were 14 ft. high and had an average thickness of 2½ ft. Therefore each side wall averaged nearly 1.3 cu. yds. per lin. ft., and the two walls averaged 2.59 cu. yds. per lin. ft. of tunnel. The concrete was mixed 1-3-5, being, we believe, unnecessarily rich in cement. The average amount of concrete placed in the walls per day was 50 cu. yds. Cost of Side Walls. Materials-- Per cu. yd. 1.33 bbl. cement at $2.00 $2.66 0.5 cu. yd. sand at 0.18 0.09 0.75 cu. yd. stone at 0.55 0.41 ------- Total $3.16 Labor on concrete-- 0.01 day foreman at $5.00 $0.05 0.03 day foreman at $3.00 0.09 0.03 day engineman at $3.00 0.09 0.35 day laborer at $1.75 0.61 ------- ------- 0.42 Total $0.84 Labor, removing timber, building forms, excavating, etc.-- 0.02 day foreman at $5.00 $0.10 0.05 day foreman at $3.00 0.15 0.40 day laborer at $1.75 0.70 ------- ------- 0.47 Total $0.95 Miscellaneous-- 0.02 day engineer and superintendent at $5.00 $0.10 Falsework and forms, timber and iron 0.07 Tools, light, etc. 0.10 Interest and depreciation of $1,800 plant at 20% per annum 0.09 Train service, 0.03 day work train at $25 0.75 Summary concrete side walls-- Per cu. yd. Materials $3.16 Labor on concrete 0.84 Labor removing timber, etc. 0.95 Train service 0.75 Miscellaneous 0.34 ------- Total $6.04 In the two side walls there were 2.59 cu. yds. of concrete per lin. ft. of tunnel, hence the cost of the side walls was $6.04 × $2.59 = $15.64 per lin. ft. of tunnel. The concrete arch varied in thickness, averaging from 14 to 20 ins. at the springing line to 8 to 14 ins. at the crown. The arch averaged 1.2 cu. yds. per lin. ft. of tunnel. About 20 cu. yds. of arch were placed per day. The arch concrete was mixed 1-3-5 and the cost was as follows: Cost of Concrete Arch. Materials-- Per cu. yd. 1.36 bbls. cement, $2.00 $2.72 0.05 cu. yd. sand, 0.18 0.09 0.75 cu. yd. stone, 0.55 0.41 ------- Total $3.22 1.8 cu. yds. dry rock backing at 0.55 $0.99 Labor on concrete-- 0.02 day foreman at $5.00 $0.10 0.12 day foreman at 3.00 0.36 0.88 day laborer at 1.75 1.54 ------- ------- ------ 1.02 Total $1.96 $2.00 Labor placing 1.08 cu. yds. rock backing-- 0.01 day foreman at $5.00 $0.05 0.51 day foreman at 3.00 0.15 0.55 day laborer at 1.75 0.96 ------- ------- ------- 0.61 Total $1.90 $1.16 Labor removing timbers, forms, excavations, etc.-- 0.02 day foreman at $5.00 $0.10 0.04 day foreman at 3.00 0.12 0.06 day carpenter at 2.50 0.15 0.40 day laborer at 1.75 0.70 ------- ------- ------- 0.52 Total $2.06 $1.07 Train service-- 0.06 day at $25 $1.50 Miscellaneous-- Engineering and superintendence. .07 Falsework, timber and iron .13 Tools, light, etc .12 Interest and depreciation, $1,800 plant, 20% per annum 0.09 Summary concrete arch-- Concrete materials $3.22 Dry rock backing (1.8 c. y.) 0.99 Labor and concrete 2.00 Labor placing 1.8 cu. yds. rock backing 1.16 Labor removing timber, etc 1.07 Train service hauling materials 1.50 Engineering and superintendence 0.07 Falsework, timber and iron 0.13 Tools, light, etc. 0.12 Interest and depreciation plant 0.09 ------ Grand total $10.35 It will be noted that the "train service" is an item that really should be considered as a part of the cost of the materials, for the cost of the sand and stone is the cost f. o. b. cars at the sand pit and at the quarry, to which should be added the cost of hauling them to the tunnel--to-wit, the "train service." Summing up, we have the following as the cost per lineal foot for lining this single-track tunnel with concrete: Per lin. ft. 2.59 cu. yds. side walls at $6.04 $15.64 1.20 cu. yds. arch at 10.33 12.40 ------- ------ ------- 3.79 cu. yds. Total $9.38 $28.04 It should be remembered that the higher cost of the arch concrete is due in large measure to the fact that 1.8 cu. yds. of dry rock packing above the arch are included in the cost of the concrete. Strictly speaking, this dry rock packing should not be charged against the arch concrete, and, segregating it, we have the following: Per lin. ft. 2.59 cu. yds. concrete side walls at $6.04 $15.64 1.20 cu. yds. concrete arch at 8.18 9.82 2.16 cu. yds. dry rock at 0.55 1.19 Labor placing 2.16 cu. yds. at 0.64 1.39 ------ Total $28.04 This is a much more rational analysis of the cost and a still further reduction in the cost of the arch concrete might be made by prorating the train service item ($1.50 per cu. yd. concrete). At least half of this train service should be charged to the dry rock backing, for there are 1.25 cu. yds. of sand and broken stone to 1.80 cu. yds. of dry rock backing. The amount of this dry rock backing, or packing, varies greatly in different parts of a tunnel. In the first half of this tunnel it averaged 1.8 cu. yds. per lin. ft., while in the second half it averaged nearly 2.4 cu. yds. per lin. ft. ~METHOD OF MIXING AND PLACING CONCRETE FOR A TUNNEL LINING.~--The tunnel known as the Burton tunnel is located on the Jasper-French Lick extension of the Southern Ry., and about 4 miles from French Lick, Ind. It is a single track tunnel 2,200 ft. long with 300 ft. at one end on a 4°-30' curve and 1,900 ft. on tangent. The material penetrated was slate and loose rock, requiring solid timbering throughout. This timbering is shown by Fig. 138, which also shows the concrete lining; the timbering was embedded in the concrete lining. [Illustration: Fig. 138.--Sections Showing Concrete Lining for Burton Tunnel.] The original timber lining was composed as follows: Posts 10×12 ins. and spaced 3 ft. apart were set on 3×12-in. sills and carried 10×12-in. wall plates which supported 10×12-in. segmental arch ribs spaced 3 ft. apart. The lagging behind the posts was 3×6-in. stuff and the lagging over the arch ribs was 4×6-in. stuff. The section of the concrete lining is shown by Fig. 138, it required 4,132 cu. yds. of concrete and 161.43 lbs. of reinforcement per lin. ft. The concrete was a 1-2½-5 crushed stone--between 2 in. and ¼ in. size--mixture; it required 1.16 bbls. of cement, 0.52 cu. yds. sand and 0.92 cu. yds. of stone per cubic yard of concrete. The amount of reinforcement per cubic yard of concrete was 39.1 lbs. [Illustration: Fig. 139.--View of Mixer Plant Showing Car Tracks, Burton Tunnel.] [Illustration: Fig. 140.--View of Mixer Plant Showing Method of Unloading Materials, Burton Tunnel.] All the concrete was mixed and handled from one end of the tunnel. The mixing plant was located in the approach cut at one end. A standard gage main track ran through the cut. About 20 ft. in the clear to one side of this track a trestle 500 ft. long was built, carrying an 18-ft. gage derrick track and a narrow gage 3-cu. yd. dump car track. A stiff leg derrick operating a 1 cu. yd. orange peel or a 1½ cu. yd. clam-shell Hayward bucket was mounted on a carriage traveling on the 18-ft. gage track. The side of the trestle nearest the railway track was sheeted vertically and the space between this sheeting and the track was floored over at track level for stock piles. Near the end of the trestle toward the tunnel and on the same side of the track was the mixer plant. This consisted of two 85 cu. yd. bins, one for sand and one for stone, carried by a tower so that their bottoms were 25 ft. above track level. Below the bins was a charging platform pierced by a measuring hopper. Below the measuring hopper was a 1½ cu. yd. cubical mixer and below the mixer was a 3-ft. gage track for 1½ cu. yd. Koppel side dump cars. To the rear of the tower at ground level there was a 20-cu. yd. sand bin and a 20-cu. yd. stone bin set side by side with a continuous bucket elevator leading from each to the corresponding bin on the tower. The cement house was located directly across the railway track from the tower. At the side of the cement house nearest the track there was an inclined bag elevator leading up to a bridge spanning the railway track at the level of the charging floor of the mixer plant. On this bridge ran a car for carrying bags of cement. The plant as described is shown by Figs. 139 and 140. In operation the derrick unloaded the stone and sand cars by means of the Hayward buckets either into the bins at the feet of the bucket elevators or onto stock piles on the flooring beside the trestle. When put into stock piles the materials had to be reloaded by derrick into the 3 cu. yd. cars on the trestle narrow gage track and carried by these cars to the elevator boots. The sand and stone were chuted from the tower bins directly into the charging hopper below. Here the cement bags, brought across the bridge on the car into which they were loaded directly by the bag elevator, were opened and the cement added to the sand and stone. The charge was then dropped into the mixer and from the mixer the batch dropped into the Koppel concrete cars. In the tunnel a traveling platform was constructed on two standard gage flat cars so coupled that a platform 100 ft. long and slightly narrower than the clear space between side wall forms was obtained. Connecting the end of the platform toward the mixing plant was a rampe or inclined platform mounted on wheels. The Koppel car tracks from the mixer were carried up the incline and the full length of the level platform. The cars were hauled to the foot of the incline by a light locomotive. A cable was then hooked to them; this cable was run through a block on the level platform, its free end coming back to the locomotive, which thus pulled the cars up the incline by moving back toward the mixer. On the level platform the cars were pushed by hand and dumped on the floor, whence the concrete was shoveled into the forms. The platform construction deserves mention in the particular that it provided for adjusting the platform vertically. At each corner of the car a vertical post some 7 or 8 ft. high was set up. The side stringers of the platform carried two vertical posts at each end; these two posts were spaced just far enough apart to slide over the corner post, one on each side of it. A block at the top of the corner posts with the hoist line connected to the bottoms of the platform posts and the lead line going to a winch head, thus made it possible to lift the platform any distance within the height of the vertical post guide and hold it there by blocking under the posts. The arrangement is shown roughly by the sketch, Fig. 141. There was block and tackle for each corner post and a winch at each end of the car. The vertical movement of the platform was between 6 and 7 ft. The floor was cemented first, then the side walls and finally the roof arch. Floor construction was begun at the portal farthest from the mixing plant. Koppel car tracks were laid through the tunnel and the concrete was dumped from them directly on the ground. The cars were hauled by a light locomotive. As the concreting advanced the dump car track was raised and suspended from timbers across tunnel so that the concrete could be placed under it. As fast as the floor hardened the permanent standard gage track was laid and a temporary third rail placed to give also a dump car track. [Illustration: Fig. 141.--Sketch Showing Telescopic Support for Concreting Platform, Burton Tunnel.] When the floor had been finished the side walls were constructed, using the traveling platform and beginning at the far portal. The wall forms consisted of 4×6-in. studs, spaced 3 ft. apart and carrying 2×12-in. lagging. A 6×6-in. waling outside the studs at about mid-height held the studs to the timbering by lag bolts reaching through the wall to the 10×12-in. posts. A strip of plank nailed across wall between stud and post held the form at the top. Wall forms were erected for 100 ft. of wall at a time. These forms required about 45 ft. B. M. lumber per lineal foot of form on one side or 90 ft. B. M. for both sides. Two sets of side wall forms or 200 ft. of wall forming were built, and used over and over again. The concrete was shoveled into the wall forms from the traveling platform, the lagging being placed a board at a time as the work progressed upward and the platform being elevated as required, its final position being at about springing line level. When 100 ft. of side walls had been completed the traveling platform was moved ahead for another 100-ft. section. [Illustration: Fig. 142.--Sketch Showing Device for Removing Centering Ribs, Burton Tunnel.] The centers consisted of 6×12-in. ribs, made up of 3×12-in. plank. The feet of the ribs rested on folding wedges on 6×12-in. wall plates, supported by 6×6-in. posts setting close against the finished wall. The ends of the ribs were held from closing in by 6×6-in. walings, one on each side, lag-bolted through the lining to the timbering. The centering required about 315 ft. B. M. of lumber per lineal foot of center. The method of removing the centers was novel. A flat car had erected on it a narrow working platform high enough to reach well up into the arch. Along this platform at the center was erected a sort of "horse," which could be elevated and lowered by jacks. The sketch, Fig. 142, shows the arrangement. At each end and at the middle of the platform two guide posts a a were erected and braced upright. Between these guide posts set plunger posts which were raised and lowered by screw jacks. The three plunger posts carried a longitudinal timber c. The car was run under the ribs of centering to be removed and the timber c raised by working the jacks until it came to close bearing under the ribs d. The railings and the wedges at the foot of the ribs were then removed, leaving the ribs hanging on the timber c. This timber was then jacked down to clear the lining and the ribs rotated horizontally on the point of suspension as a pivot until their ends swung in over the platform. The car was then moved ahead to where the centers were to be used again; the ribs were rotated back to their normal position across tunnel; the timber c was jacked up, and the wedges and railings placed at the first of the ribs. The concreting on the roof arch was begun at the portal. Two shifts were worked and 42 ft. of arch were concreted each shift. ~METHOD AND COST OF LINING GUNNISON TUNNEL.~--The costs are for concrete in place in the side walls and the arch of the tunnel, for a length of 440 lin. ft. The quantity of concrete considered in estimating the cost per cubic yard was 616 cu. yds. The material was mixed and placed in ½ cu. yd. batches, the proportion of the mixtures being 1-2.2-4.4. The final cost includes the labor of excavating and screening gravel and sand, the hauling of the same from the bins at the pit to the storage bins at the main shaft, the care of the chutes in the shaft and the mixing of the concrete in the tunnel at the bottom of the shaft, the transportation of the concrete from the mixer to the traveler, the deposition of the concrete, the setting up and taking down of forms and the cost of the cement. It does not include the construction of the gravel pit chutes that hold the screens, the building of the road from the gravel pit to the storage bins at the shaft, the concrete mixer and its installation, the traveler and its installation, the cost of material and labor in the construction of the concrete forms, the requisite power to run the machinery and other expenses of a similar nature. The gravel used for the concrete was obtained from a pit situated on top of a hill not far from the main shaft leading down to the tunnel. This gravel bed contains very closely the proper proportions of sand and gravel for the concrete aggregates. The gravel was excavated and loaded by hand into side dump cars of 35 cu. ft. capacity. These cars were run to the edge of the hill where the gravel was dumped upon a screen from which it ran by gravity, passing thence into storage bins. From the storage bins the sand and gravel were drawn off into dump wagons having a capacity of 2 cu. yds. and hauled a distance of one-half mile to a second set of storage bins located at the top of the shaft leading into the tunnel. The road from the storage bins at the gravel pit to the storage bins at the head of the shaft was down grade. A two-horse team could readily haul 2 cu. yds. of gravel over this road. The storage bins at the top of the shaft leading into the tunnel communicated with the measuring boxes at the bottom of the shaft by means of chutes. The measuring boxes discharged directly into tram cars. The average length of haul from the mixer to the place of deposition of concrete was about 4,500 ft. The concrete was placed in the side walls by means of a traveler, which was so operated in the tunnel as to allow the passage of the concrete trains beneath it. The traveler was 64 ft. long and was provided with a slow motion electric hoist, by which the cars containing the concrete were elevated to the top of the traveler and thence transferred to any desired position. The concrete was dumped from these cars into boxes where any remixing or tempering that was required was done, after which the concrete was shoveled directly into the forms. The entire operation of handling the materials of the concrete, it will be seen, utilized gravity to the greatest possible degree. In order to get a good average cost per cubic yard for handling gravel and sand, this analysis has been based on five months' operation, from November, 1906, to March, 1907. In these five months there were 4,123 cu. yds. of sand and gravel handled. The concrete considered was placed during the month of March. Below is given the distribution of the cost of the concrete as to the specified divisions of the work and as to the class of work involved in each division. Measurements taken at the mixer show that each cubic yard of concrete contained 0.74 cu. yds. of gravel, 0.445 cu yds. of sand and 5.6 sacks of Portland cement. The total of the aggregates is, therefore, 1.185 cu. yds. per cubic yard of concrete. The cement costs $0.62 per sack on the work, making a cost of $3.472 per cubic yard of concrete. Excavating and screening 4,123 cu. yds. gravel-- Total Per cu. yd. cost. gravel. Foreman, 66-7/8 days at $3.04 $ 203.30 $0.049 Labor, 397½ days at $2.56 1,017.60 0.247 Labor, 116¼ days at $2.08 241.80 0.059 -------- ------ Total $1,462.70 $0.355 Hauling 4,123 cu. yds. gravel and sand-- 2-horse team and driver, 210 days at $3.60 $756.00 $0.183 2-horse team and driver, 4½ days at $4 18.00 0.005 ------- ------ Total $774.00 $0.188 As there were 1.185 cu. yds. of gravel per cubic yard of concrete the cost of gravel per cubic yard of concrete was for-- Excavating and screening (1.185 × $0.355) $0.421 Hauling (1.185 × $0.188) 0.223 ------ Total $0.644 Adding to this the cost of cement $0.62 × 5.6 = $3.472, we have $0.644 + $3.472 = $4.116, as the cost of concrete materials per cubic yard of concrete. The cost of labor, mixing and placing was as follows for 616 cu. yds.: Total Per cu. yd. Mixing 616 cu. yds. concrete-- cost. concrete. Superintendent, 2 days at $5.83-1/3 $ 11.67 $0.020 Foreman, 1 day at $4.50 4.50 0.007 Labor, 45 days at $3.04 130.72 0.215 Labor, 93 days at $2.56 238.08 0.381 Hoist engineer, 34 days at $3.52 119.68 0.196 ------- ------ Total $504.65 $0.819 Transporting 616 cu. yds. concrete-- Superintendent, 1 day at $5.83-1/3 $ 5.83 $0.009 Foreman, 1 day at $4.50 4.50 0.007 Motorman, 34 days at $3.04 103.36 0.175 Brakeman, 34 days at $2.56 87.04 0.135 ------- ------ Total $200.73 $0.326 Depositing 616 cu. yds. concrete-- Superintendent, 4 days at $5.83-1/3 $ 23.33 $0.038 Foreman, 4 days at $4.50 18.00 0.029 Foreman, 68 days at $3.04 200.72 0.326 Labor, 238½ days at $2.56 610.56 0.991 ------- ------ Total $852.61 $1.384 Setting and moving forms-- Superintendent, 2 days at $5.83-1/3 $ 11.67 $0.018 Foreman, 2 days at $4.50 9.00 0.014 Carpenter foreman, 10 days at $5 50.00 0.080 Carpenter, 13 days at $3.20 41.60 0.067 Labor, 49 days at $3.04 148.96 0.241 Labor, 19 days at $2.56 48.64 0.078 ------- ------ Total $309.87 $0.498 Summarizing we have the following cost: Materials-- Cement, 5.6 bags at $0.62 $3.472 Gravel (excavating and screening) 0.421 Hauling gravel and sand 0.223 ------ Total, materials $4.116 Labor-- Mixing concrete $0.819 Transporting concrete 0.326 Depositing concrete 1.394 Setting and moving forms 0.498 ------ Total, labor $3.037 Grand total $7.153 ~COST OF CONCRETE WORK IN LINING NEW YORK RAPID TRANSIT SUBWAY.~--The costs given here refer alone to the concrete work in constructing the jack arch and steel beam lining of the original standard subway. Figure 143 shows the character of this construction. Arch panel forms were set up between the wall beams and hung from the floor beams and filled behind and above with 1-2-4 trap rock concrete. The form panels were used over and over and the concrete was machine mixed. Common labor was paid $1.50 per 8-hour day; foremen, $3; carpenters, $3; enginemen, $3.50; and masons, $4. The costs cover three sections and are in each case the averages for the whole section. They are, we believe, the only itemized costs that have been published for concrete work on this road. [Illustration: Fig. 143.--Cross-Section of New York Rapid Transit Subway.] _Two-Track Subway._--In this section of two-track subway there were 8,827 cu. yds. of foundation concrete and 6,664 cu. yds. of concrete in wall and roof arches. The two classes of work cost as follows: Foundations-- Total. Per cu. yd. Labor mixing $ 4,669 $0.53 Labor placing 5,142 0.58 Materials and plant 211 0.02 Cement, sand, stone, etc. 30,719 3.48 -------- ------- Total $40,741 $4.61 Roof and side walls-- Labor mixing $ 5,444 $0.82 Labor placing 5,623 0.84 Labor setting forms 14,746 2.21 Labor plastering arches 431 0.06 Materials and plant 1,176 0.18 Cement, sand, stone, etc. 23,888 3.58 -------- ------ Total $51,308 $7.69 Averaging the work we have 15,491 cu. yds. of concrete placed at a cost of $5.94 per cu. yd. _Four-Track Subway._--On two sections of four-track subway the labor cost of mixing and placing concrete similarly divided was as follows: Section A. Section B. Foundations-- Per cu. yd. Per cu. yd. Labor mixing $0.97 $0.94 Labor placing 0.96 0.95 Power 0.14 0.16 -------- -------- Total $2.07 $2.05 Roof and side walls-- Labor mixing $0.79 $0.91 Labor placing 0.85 0.94 Labor setting forms 2.01 1.20 Labor plastering arches 0.16 0.23 Power 0.28 0.15 ------- ------- Total $4.09 $3.43 [Illustration: Fig. 144.--Traveling Form for Side Walls, New York Subway Tunnels.] ~TRAVELING FORMS FOR LINING NEW YORK RAPID TRANSIT RY. TUNNELS.~--In constructing the tunnels under Park Ave. and under the north end of Central Park for the New York Rapid Transit Ry., traveling centers and side wall forms were used for the concrete lining. The mixing plants were installed in the shafts and consisted generally of gravity mixers charged at the surface and discharging into skip cars running on the tunnel floor. [Illustration: Fig. 145.--Traveling Form for Roof Arch. New York Subway Tunnels.] The forms used in the Park Ave. tunnel are shown by Figs. 144 and 145; those used in the Central Park tunnel differed only in details. The method of work was slightly different in the two tunnels, but was substantially as follows: Three platforms mounted on wheels were used in each set and two sets were employed. Ahead came a traveler carrying the side wall forms, next came a shorter traveler carrying a derrick, and last came the traveler carrying the roof centers. The arrangement as operated in the Central Park tunnel is shown by Fig. 146. In the Park Ave. tunnel the "bridges" were dispensed with, the skips being hoisted through the open end bays of the derrick car and set directly on the cars on the center traveler. [Illustration: Fig. 146.--Sketch Plan of Traveling Forms, New York Subway Tunnels.] The traveler carrying the side wall forms was set in position and blocked, the grade and line being given by the track rails, which had been set exactly for that purpose. The side wall forms differed slightly in the two tunnels; those for the Park Ave. tunnel shown by Fig. 144 formed the vertical portion of the wall only so that when the arch forms, Fig. 145, followed a space A B was left which had to be molded by separate sector-like forms. The side wall forms for the Central Park work were constructed as shown by Fig. 147, being curved at the top to merge into the arch centers. In the Park Ave. work the wall studs were adjusted in or out by means of wedges and slotted bolt holes. In the Central Park work the studs A Fig. 145 were hung by ¾-in. bolts from the pieces B spiked to line onto the cross-braces. The bottom was then lined up by means of wedges at D. The side wall studs being lined up, the bottom lagging boards were placed and filled behind by shoveling the concrete into them direct from skip cars on the adjacent tracks on the tunnel floor. In this way the side walls were built up to the tops of the forms. [Illustration: Fig. 147.--Sketch Showing Detail of Side Wall Forms. New York Subway Tunnels.] As soon as the side wall concrete had set the forms were struck and the traveler was moved ahead and set for another section of wall. The derrick and roof arch travelers were then moved into position between the finished walls, and the arch traveler was jacked up and aligned. Skip cars coming from the mixer were run under the derrick traveler, where the skips were lifted by the derrick and set on the platform cars to be run alongside the work. The arch lagging was placed a piece at a time and filled behind by shoveling direct from the skips. As the crown was approached the lagging was placed in short lengths and filled in over the ends, the concrete being shoveled in two lifts; in Fig. 145 the line C D indicates the position of the shoveling board. The centers were struck by lowering the jack supported traveler down onto the track rails. ~COST OF MIXING AND PLACING SUBWAY LINING, LONG ISLAND R. R., BROOKLYN, N. Y.~--The subway carrying the two tracks of the Long Island R. R. under Atlantic Ave., in Brooklyn, New York city, has a lining consisting of an invert arch 12 ins. thick at the center, side walls 4½ ft. thick at the base and 3 ft. thick at the top, and a roof of jack arches between steel I-beams 5 ft. apart. The dimensions inside the concrete are 16×20 ft. A 1-8 mixture of cement, sand, gravel and stone was used in the floor and walls and a 1-6 mixture of the same materials in the jack arches. A bag of cement was called 1 cu. ft., so that a barrel was 4 cu. ft. A Hains gravity mixer and a batch mixer were used and careful records were kept of all quantities. _General Data._--During 1903, about 13,880 cu. yds. of the 1-8 concrete were placed, 90 per cent. of which was mixed in the gravity mixer and 10 per cent. in the batch mixer. Of the 1-6 concrete 5,320 cu. yds. were placed, 85 per cent, of which was mixed in the gravity mixer and 15 per cent, in the batch mixer. _Gravity Mixer Work._--During 1903, there were 16,940 cu. yds. of concrete mixed in gravity mixers, requiring 2,860 days' labor mixing and 4,000 days' labor placing. Wages were $1.50 a day and the cost was 26 cts. per cu. yd. for mixing and 33 cts. for placing, making a total of 59 cts. per cu. yd. During the month of August when 2,800 cu. yds. were mixed the cost was as low as 24 cts. for mixing, plus 22 cts. for placing, or a total of 46 cts. per cu. yd. for mixing and placing. The mixer averaged about 113 cu. yds. per day with a gang of 19 men mixing and 26 men placing. The average size of batch was 0.46 cu. yd. In 1904, 20,000 cu. yds. were mixed in 190 days, worked with a gang of 19 men mixing; the gang placing consisted of 25 men. The cost was as follows: Item. Total. Per cu. yd. 2,950 days labor mixing $ 4,870 24 cts. 4,760 days labor placing 7,300 36 cts. --------- -------- Total $12,170 60 cts. During the best month of 1904, the labor cost was 16 cts. for mixing and 29 cts. for placing, or a total of 45 cts. per cu. yd. _Batch Mixer Work._--During 1903 the batch mixer mixed 2,390 cu. yds. in 970 labor days mixing and 740 labor days placing at a cost of 59 cts. per cu. yd. for mixing and 55 cts. per cu. yd. for placing, or a total of $1.04 per cu. yd. During the month of June the cost was as low as 40 cts. for mixing and 30 cts. for placing, or 70 cts. per cu. yd. for mixing and placing. The wages paid were $1.50 per day and the average gangs were 11 men mixing and 14 men placing; the average batch mixed was 0.57 cu. yd. and the average output was 35 cu. yds. per day. During 1904, the mixer worked 153 days and averaged 46 cu. yds. per day; the average size of batch was 0.44 cu. yd. The average gangs were 13 men mixing and 11 men placing. The labor cost of 7,000 cu. yds. was as follows: Item. Total. Per cu. yd. 1,910 days labor mixing $3,175 45 cts. 1,740 days labor placing 2,660 38 cts. ------- -------- Total $5,835 83 cts. _Haulage._--The costs given comprise in mixing, the cost of delivering the materials to the mixer, and, in placing, the cost of hauling the concrete away. A Robins belt conveyor was used to deliver materials to the gravity mixer and this accounts, in a large measure, for the lower cost of mixing by gravity. The mixed concrete was hauled from both mixers in dump cars pushed by men. _Form Work._--The labor cost of forms for 19,300 cu. yds. of concrete placed in 1903 was $16,800, or 87 cts. per cu. yd. of concrete. The total labor days consumed on form work was 6,340 at $2.70 per day. The total cost of concrete in place for mixing, placing and form work was $1.46 per cu. yd., not including lumber in forms, fuel, interest and depreciation.