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diff --git a/17302-8.txt b/17302-8.txt new file mode 100644 index 0000000..ab95d13 --- /dev/null +++ b/17302-8.txt @@ -0,0 +1,1677 @@ +The Project Gutenberg EBook of Transactions of the American Society of +Civil Engineers, vol. LXVIII, Sept. 1910, by B.F. Cresson, Jr + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: Transactions of the American Society of Civil Engineers, vol. LXVIII, Sept. 1910 + The New York Tunnel Extension of the Pennsylvania Railroad + The Terminal Station - West + +Author: B.F. Cresson, Jr + +Release Date: December 13, 2005 [EBook #17302] + +Language: English + +Character set encoding: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK SOCIETY OF CIVIL ENGINEERS *** + + + + +Produced by Juliet Sutherland, Sigal Alon and the Online +Distributed Proofreading Team at https://www.pgdp.net + + + + + + + + + + +AMERICAN SOCIETY OF CIVIL ENGINEERS + +INSTITUTED 1852 + + +TRANSACTIONS + +Paper No. 1156 + + +THE NEW YORK TUNNEL EXTENSION OF THE +PENNSYLVANIA RAILROAD. + +THE TERMINAL STATION-WEST.[A] + +BY B.F. CRESSON, JR., M. AM. SOC. C.E. + + + + +_Location of Work._--The area covered by the work of the Terminal +Station-West is bounded as follows: By the east line of Ninth Avenue; by +the south side of 31st Street to a point about 200 ft. west of Ninth +Avenue; by a line running parallel to Ninth Avenue and about 200 ft. +therefrom, from the south side of 31st Street to the boundary line between +the 31st and 32d Street properties; by this line to the east line of Tenth +Avenue; by the east line of Tenth Avenue to the boundary line between the +32d and 33d Street properties; by this line to the east line of Ninth +Avenue. The area is approximately 6.3 acres. + +_House-Wrecking._--The property between Ninth and Tenth Avenues was covered +with buildings, 94 in number, used as dwelling and apartment houses and +church properties, and it was necessary to remove these before starting the +construction. Most of the property was bought outright by the Railroad +Company, but in some cases condemnation proceedings had to be instituted in +order to acquire possession. In the case of the property of the Church of +St. Michael, fronting on Ninth Avenue, 31st and 32d Streets, the Railroad +Company agreed to purchase a plot of land on the south side of 34th Street, +west of Ninth Avenue, and to erect thereon a church, rectory, convent, and +school, to the satisfaction of the Church of St. Michael, to hand over +these buildings in a completed condition, and to pay the cost of moving +from the old to the new buildings, before the old properties would be +turned over to the Railroad Company. + +The house-wrecking was done by well-known companies under contract with the +Railroad Company. These companies took down the buildings and removed all +the materials as far as to the level of the adjacent sidewalks. The +building materials became the property of the contractors, who usually paid +the Railroad Company for the privilege of doing the house-wrecking. The +work was done between April and August, 1906, but the buildings of the +Church of St. Michael were torn down between June and August, 1907. + +The bricks were cleaned and sold directly from the site, as were +practically all the fixtures in the buildings. The stone fronts were broken +up and left on the premises. Some of the beams were sold on the premises, +but most of them were sent to the storage yards. Some of the lath and +smaller timber was sold for firewood, but most of it was given away or +burned on the premises. + +_Contracts and Agreements._--The main contract, awarded to the New York +Contracting Company-Pennsylvania Terminal on April 28th, 1906, included +about 502,000 cu. yd. of excavation (about 90% being rock), 17,820 cu. yd. +of concrete walls, 1,320,000 lb. of structural steel, 638,000 ft., B.M., of +framed timber, etc., etc. + +This contract was divided into two parts: "Work In and Under Ninth Avenue" +and "Work Between Ninth and Tenth Avenues," and unit prices were quoted for +the various classes of work in each of these divisions. The prices quoted +for excavation included placing the material on scows supplied by the +Railroad Company at the pier at the foot of West 32d Street, on the North +River; there was a clause in the contract, however, by which the contractor +could be required to make complete disposal of all excavated material at an +additional unit price, and this clause was enforced on January 1st, 1909, +when about 94% of the excavation had been done. + +For the purpose of disposing of the excavated material in the easterly +portion of the Terminal, the New York Contracting Company-Pennsylvania +Terminal had excavated under Ninth Avenue a cut which came to the grade of +32d Street about midway between Ninth and Tenth Avenues, and a trestle was +constructed from this point over Tenth Avenue and thence to the disposal +pier at the foot of West 32d Street. + +On May 11th, 1906, the work of excavation was commenced on the east side of +Ninth Avenue, and on July 9th, 1906, on the south side of 31st Street, +between Ninth and Tenth Avenues. From the beginning, the excavation was +carried on by day and night shifts, except on Sundays and holidays, until +January, 1909, except that during the period from November, 1907, to +October, 1908, the night shift was discontinued. + +_Geology._--The rock encountered may be classed as "gneiss"; its character +varied from granite to mica schist. It was made up of quartz, feldspar, and +mica, and there were also some isolated specimens of pyrites, hornblend, +tourmaline, and serpentine. On the south side of the work, just west of +Ninth Avenue, there were excellent examples of "contortions" of veins of +quartz in the darker rock. On the east side of Ninth Avenue, near the north +end of the work, glacial marks were found on the rock surface. The general +direction of the stratification was north 5° west, and the general incline +about 60° with the horizontal. As a rule, the rock broke sharply along the +line of stratification. On the south side it broke better than on the north +side, where it was usually softer and more likely to slide; and this, +together with the fact that in winter it was subject to alternate freezing +and thawing and in summer to the direct rays of the sun, made it rather +difficult to get a good foundation for the retaining walls. + + +WORK IN AND UNDER NINTH AVENUE. + +_General Description._--The work involved the excavation of about 375 ft. +of the full width of Ninth Avenue to an average depth of about 58 ft., and +the construction over this area of a steel viaduct, the deck of which was +about 24 ft. below the surface, for the ultimate support of the Ninth +Avenue structures. + +The following estimated quantities appear in the contract: Excavation of +rock, 72,600 cu. yd.; excavation of all materials except rock, 9,300 cu. +yd.; concrete (1:3:6) in abutments, etc., 1,680 cu. yd.; timber, 504,000 +ft., B.M.; structural steel, 1,320,000 lb., etc. + +While this excavation was being done it was necessary to support and +maintain the three-track elevated railway structure of the Interborough +Rapid Transit Company, of which 18 columns, or a length of about 340 ft., +were affected, the two-track surface railway structure of the New York City +Railway Company, and various pipes, sewers, and conduits, and to maintain +all surface vehicular and pedestrian traffic. All structures were left in +place with the exception of the pipes, most of which were temporarily cut +out. The 48-in. brick sewer in the center of Ninth Avenue was broken, and +the sewage was pumped across the excavation through a smaller pipe. + +The general method adopted was as follows: The east and west sides of the +avenue were closed, vehicular traffic was turned into the center, and a +trestle for pedestrians was constructed west of the westerly elevated +railway columns. All structures were then supported on transverse girders, +running across the avenue, below the surface, and these rested on concrete +piers on the central rock core. The sides of the avenue were then excavated +to sub-grade, and the permanent steel viaduct was erected on both sides of +the avenue as close as possible to the central rock core. The weight of all +structures was then transferred to the permanent steel viaduct, erected on +the sides of the avenue, by timber bents under the transverse girders +resting on the permanent steel viaduct, and all weight was thus taken off +the central rock core. This core was then excavated to sub-grade, the +permanent viaduct was completed, and all structures were placed on its +deck, using concrete piers and timber bents. + +The design and erection of the permanent steel viaduct and the permanent +foundations on its deck were done under another contract, apart from the +North River Division work, and are not described in this paper. + +_Elevated Railway Structure of the Interborough Rapid Transit +Company._--The Ninth Avenue Elevated Railway was built between 1877 and +1880 as a two-track structure, the design being such as to permit a third +or central track to be added later, and this was built in 1894. It is +supported on columns under the outside tracks, about 43 ft. from center to +center longitudinally and 22 ft. 3 in. from center to center transversely, +the central track being carried by transverse girders between the columns. + +The columns carrying the structure are of fan top design, with the points +of bearing near the extremities at the top; each of the outside tracks is +supported on two longitudinal latticed girders and the central track on +two plate girders; between the columns, transverse girders are spliced to +the outside track cross-frames, and carry the central track system. It was +not thought desirable to put brackets on the columns near the street level +to support the structure temporarily, and, as there is an expansion joint +at each column, and as the transverse girders carrying the central track +system are not rigidly attached to the longitudinal girders carrying the +outside tracks, the central track could not be supported by supporting the +outside tracks; therefore, independent supports for each track, in the form +of overhead girders, had to be provided. The columns rest on brick piers, +each having four 2-in. anchor-bolts. The brick foundations on the west side +are wide in order to allow a 24-in. water main to pass directly beneath the +columns. The foundations are usually on rock. + +[Illustration: PLATE XLVII, FIG. 1.--TW 4, P.N.Y. & L.I.R.R. Terminal +Station West. View of 9th Ave. looking Northwest from 32nd Street, prior to +commencement of work. April 23, 06.] + +[Illustration: PLATE XLVII, FIG. 2.--TW 17, P.N.Y. & L.I.R.R. Terminal +Station West. View of East side of 9th Ave. looking North from a point 100 +feet south of 33rd St. showing condition of work. July 23, 06.] + +[Illustration: PLATE XLVII, FIG. 3.--TW 25, P.N.Y. & L.I.R.R. Terminal +Station West. View showing permanent and temporary supports of 9th Ave. +Structures, looking Northwest from 31st. St. April 24, 07.] + +[Illustration: PLATE XLVII, FIG. 4.--TW 28, P.T. & T.R.R. Co. Terminal +Station West. East side of 9th Avenue, North of 32nd St. looking West, +showing rock excavation and supports of 9th Avenue structures. Aug. 17, +07.] + +Fig. 1, Plate XLVII, shows the elevated railway structure and the street +surface prior to the commencement of the work. + +The east track is used for north-bound local trains, the west track for +south-bound local trains, and the central track for south-bound express +trains between 7 and 9.30 A.M. and for north-bound express trains between +2.30 and 7 P.M. It is said that an average of 90,000 passengers are carried +over this structure every 24 hours. + +_Surface Railway Structure of the New York City Railway Company._--This is +an electric surface railway of the ordinary type, the rail and slot being +bedded in concrete, with cast-iron yokes every 5 ft. There are manholes +every 100 ft., and cleaning-out holes every 15 ft. Power conduits are +bedded in the concrete on the east side of the east track. + +_Forty-eight-Inch Brick Sewer._--This sewer was in the center of Ninth +Avenue, with the invert about 12 ft. below the surface, and manholes about +100 ft. apart, and had to be abandoned in this position to allow the +transverse girders to be put in place to carry all structures while the +excavation was being done. + +_Twenty-four-Inch Cast-Iron Water Main._--This water main was laid under +the west elevated railway columns, with its top about 3 ft. below the +surface, a space being left for it in the brick foundations, and a large +column base casting being used to span it. Valves were installed, one north +of 33d Street and one south of 31st Street, prior to excavating near the +pipe, so that if it was broken the water could be shut off promptly. + +_Street Surface._--It was the original intention to close and excavate the +east side of the avenue and to erect there a street-traffic trestle before +closing the west side, but, at the contractor's request, both sides were +closed, and all vehicular traffic was turned into the center. A light +trestle on the west side of the avenue provided for pedestrian traffic. + +_Other Sub-surface Structures._--There were various gas mains, water mains, +electric conduits, manholes, hydrants, etc., in the avenue, and most of +these were cut out temporarily, at the contractor's request, to be replaced +subsequently. + +_Supports for Elevated Railway Structure._--As stated previously, the +central track had to be supported independently. + +The overhead girders, known as girders "B", were therefore designed as +shown on Fig. 1, and put in place as shown on Figs. 2 and 3. The outside +tracks were blocked directly on these girders, and the central track was +supported by blocking up the transverse girders on I-beams placed between +the girders "B"; and no blocking was placed between the girders "B" and the +longitudinal girders carrying the central track. The weight on each column +was assumed to be 172,000 lb. + +[Illustration: FIG. 1. (Full page image) + +DETAILS OF STEEL GIRDERS, ETC. SUPPORTING NINTH AVENUE STRUCTURES] + +_Supports for Surface Railway Structure._--A uniform load of 3,000 lb. per +lin. ft. of single track, with the weight of a car at 39,000 lb., was +assumed. Several feet of earth, between the structure and the rock, were +mined out, and the structure was supported on I-beams and posts, and +ultimately on the transverse girders by using timber bents under the +I-beams, as shown on Fig. 3. + +_Water Mains and Sewer._--Cradles were designed for the support of the +48-in. and 24-in. water mains, resting on the transverse girders, and the +48-in. cast-iron sewer on the east side of the avenue was carried on +I-beams bracketed to the ends of the transverse girders, as shown on Figs. +1 and 2. + +[Illustration: FIG. 2. (Full page image) + +METHOD OF SUPPORTING ELEVATED RAILWAY STRUCTURE] + +[Illustration: FIG. 3. (Full page image) + +METHOD OF SUPPORTING TRACKS OF NEW YORK CITY RAILWAY CO.] + +_Girders "C."_--The transverse girders below the street surface, referred +to above, were known as girders "C," and they were put in place at first +resting on concrete piers on the central core; the weight of all structures +was placed on them while the sides of the avenue were being excavated, and +the sides of the viaduct were being built. The ends of these girders were +then picked up on the sides of the viaduct, and, spanning the central rock +core, carried all structures while the core was being excavated and the +viaduct completed. New foundations were then placed on the deck of the +viaduct to carry all structures. + +Fifty-four of these girders were required, each weighing about 19,000 lb. +The bents carrying the ends of these girders on the sides of the viaduct +are shown on Fig. 2. They were of long-leaf yellow pine. These girders were +located so that a cradle could be laid on them east of the elevated railway +structure to carry a proposed 48-in. cast-iron water main. + +_Girders "B."_--Eighteen of these girders were required, each weighing +about 6,000 lb. The timber bents supporting these girders, shown on Fig. 2, +were of long-leaf yellow pine. + +The total weight, including the elevated railway structure, surface railway +structure, pipes, etc., supported during the work, amounted to about 5,000 +tons. + +_Details of the Work._--The method in general is shown on Figs. 4 and 5. At +first the east side of the avenue was closed and excavated down to rock, +the earth was mined out under alternate yokes of the surface railway +structure, and temporary posts were placed under the yokes to support the +structure while the remainder of the earth was being removed. Then +needle-beams and posts were placed under each yoke. The concrete forming +the track structure was then enclosed with planking to prevent it from +cracking and falling. I-beams were then placed under the needle-beams +carrying the structures, and these were carried on posts; they were changed +alternately until the excavation had been taken out to a depth of about 16 +ft. below the surface. In placing these I-beams, heavier blocking was used +in the center of the span than at the ends where the bents would come, to +prevent the subsidence of the track owing to the sag in the I-beams. As +much excavation, to a depth of about 20 ft., was taken out adjoining the +elevated railway foundations as could be done with safety. Fig. 2, Plate +XLVII, shows this condition of the work. The 48-in. brick sewer was broken, +and the sewage was pumped across the excavation. + +The overhead girders "B" were then put in place, and two of the girders "C" +were used as temporary shoring girders at each column. These, as shown by +Fig. 3, Plate XLVII, were placed parallel to the elevated railway, with +blocking between them and the girders "B." Double bents, independent +of each other, were placed under the ends of these temporary shoring +girders, and these were braced securely to prevent possible dislodgment +during the removal of the rock. The weight of the structure was then taken +by jacking up the girders near the bents until the column was lifted off +the old foundation; blocking was put in between the girders and the bents +during the jacking, so that when the jacks were released the base of the +column was still clear of the old foundation. One 80-ton jack was used for +this purpose, and the general method is shown by Fig. 1, Plate LII. + +[Illustration: FIG. 4. (Full page image) + +METHOD OF EXCAVATING NINTH AVENUE PLAN AND ELEVATION SHOWING VARIOUS STAGES +OF THE WORK] + +[Illustration: FIG. 5. (Full page image) + +METHOD OF EXCAVATING NINTH AVENUE SECTIONS SHOWING VARIOUS STAGES OF WORK + +No. 1 + +Condition Prior to Commencement of Work + +No. 2 + +East side of Avenue cut down about 20 ft. Beams with Supporting Posts +placed under Surface Railway Tracks. Girders _B_ and Temporary Shoring +Girders _C_ for supporting Elevated Ry. in place. + +No. 3 + +I's in place under Surface Ry. Tracks. Elevated Ry. carried on Temporary +Shoring Girders, and Girders _C_ in place. 24" Water Main carried on Timber +Cradle and sewage carried through Pipe _R_. Foot Walk carried on Girders +_C_ in place on West Side of Avenue. + +No. 4 + +Elevated Railway carried on Bents under Columns. Temporary Shoring Girders +removed and Permanent Bents resting on Girders _C_ in place. Bents in place +on Girders _C_ carrying Surface Railway. East and West sides of Avenue +excavated down to Sub-Grade and Five rows of Permanent Steel in place on +each side. Bents erected on Permanent Steel to catch ends of Girders _C_ +while 2 outside Concrete Piers are removed and 6th row of Permanent Steel +on each side is put in place. + +No. 5 + +Two outside Concrete Piers removed and 6th row of Permanent Steel in place. +Girders _C_ carrying all structures now resting on Bents on Permanent +Steel. 48" C.l. Sewer carried on Brackets on Girders _C_. + +No. 6 + +Excavation Completed. ] + +Temporary raker braces were placed against the structure to prevent lateral +movement. Four sets of these temporary shoring girders were used in this +manner, two sets starting at the north end and two sets at about the middle +of the work, and these sets were moved south as they were released. + +The columns being thus supported on temporary shoring girders, the old +foundations were removed and the excavation was taken down to a level about +16 ft. below the surface. + +Two sets of three of the girders "C" were then put in place under the +avenue at each column, each set being placed on four concrete piers 6 ft. +square with spaces of 4 ft. between them, so that the outside of the +outside pier would be 18 ft. from the center of the avenue and 32 ft. from +the house line. This is shown on Fig. 5 and on Fig. 3, Plate XLVII. Four +small piers were used, as they could be more easily removed than one +continuous pier. The girders "C" were set to line and grade, and the piers +were built under them, great care being taken to get the concrete well +under the girders so as to give a firm bearing. + +After these girders "C" were in place it was necessary to remove the +temporary shoring girders before the bents could be erected on girders "C" +to support girders "B," being in the same plane; and provision had to be +made to support the structure while this was being done. Therefore, double +bents were erected directly beneath the columns, as shown by Figs. 2, 4, +and 5, and by Fig. 3, Plate XLVII. These were built with their sills +resting on the girders "C," and blocking was put in between the sills and +the rock to carry the full weight of the structure. Later, when the weight +of the structure was carried on the permanent bents, this blocking was +knocked out, but the bents were left in to carry the weight of the column +itself, which was swinging more or less from the structure above. The +weight of the structure was placed on these bents directly beneath the +columns by jacking up the temporary girders again, putting blocking between +the bents and the base of the columns, and taking out the blocking which +had been put in previously under the temporary shoring girders. The 24-in. +water main was carried over the excavation on cables from the temporary +shoring girders, except when they were being jacked up, at which time posts +were placed beneath it. + +Anchor-bolts were put in place between the column bases and the bents +directly beneath, in order to increase the lateral stiffness, and raker +braces were also used. This having been done, the temporary shoring girders +were moved south to the next column, where the process was repeated. The +timber bents, shown in detail by Fig. 2, were then put in place as shown by +Figs. 4 and 5, and by Fig. 3, Plate XLVII. These bents were framed as +tightly as possible, using generally a 20-ton jack, and they were erected +simultaneously at each pair of columns. The weight was taken on these +columns by jacking up directly beneath the column base and taking out the +blocking between this base and the bent directly beneath the column. On +releasing the jack the weight was transferred to the permanent timber +bents, and the east and west columns of each pair were transferred on the +same day. One 80-ton jack was used on the easterly columns and two were +necessary on the westerly columns, one on each side of the 24-in. water +main. The raker braces of these permanent bents were not framed as tightly +as the main posts, in order that the main post should carry the entire +weight and the raker braces merely steady the structure. + +Timber bents were erected on girders "C" to carry the I-beams under the +surface railway structure, as shown on Fig. 3, and all temporary posts +under these I-beams were removed. The bents were framed with a jack, as +tightly as possible, and very little settlement of the track occurred. + +A cradle was then built under the 24-in. water main and placed on girders +"C," and, as a temporary footwalk had been constructed on the west side of +the avenue, it will be seen that all structures were thus carried on +girders "C." + +All structures were put on the girders "C" before continuing the excavation +on the sides of the avenue because, in case of a slide of rock, there would +be less danger than to individual structures. The outside piers, on +which the girders "C" rested, might even be lost, without affecting the +stability of the structure, and posting could readily be done beneath these +girders in case of necessity. + +A very careful record of levels, taken on the elevated railway columns, was +kept, observations being made during each jacking up and at least twice a +week during the progress of the work. The columns were usually kept about +1/2 in. high so as to allow for compression in the timber bents. + +As a rule, no jacking of the elevated railway structure was done while +trains were passing over, and trains were flagged during the operation. +There was generally very little delay, as all jacking was done between +10.30 A.M. and 2.30 P.M., when the traffic was lightest, and frequently the +jacking was done between trains, causing no delay whatever. Steel clamps +were placed, three on the top and three on the bottom of each set of the +girders "C," to bind them together and cause them to act as a unit. + +All structures then being supported on girders "C," which were carried on +four concrete piers resting on the central rock core, the excavation on the +sides of the avenue was continued down to sub-grade and the east and west +portions of the concrete north abutment were constructed. The central rock +core was about 36 ft. wide on the top and 45 ft. wide on the bottom, and at +the center of 32d Street it was about 42 ft. high. + +It was the original intention to excavate a sufficient width of the sides +of the avenue to erect six rows of the permanent steel viaduct, 5 ft. from +center to center, and this was done on the south portion of the work. On +the north portion, however, the rock was of poor quality, and it was +thought best to excavate for only five rows at first, to erect the five +rows of permanent steel and put the timber bents in place under the ends of +the girders "C," in order to give them some support while the outside +concrete piers were being removed and the excavation was being widened out +to permit the erection of the sixth row. Additional raker braces were put +in these bents temporarily, and were removed when the sixth row of steel +had been erected. This is shown on Figs. 4 and 5. + +[Illustration: PLATE XLVIII, FIG. 1.--TW 33, P.T. & T.R.R. Co. Terminal +Station West. East side of 9th Ave. looking North from 31st St., showing +rock excavation and supports of 9th Ave. structures. Dec. 28, 07.] + +[Illustration: PLATE XLVIII, FIG. 2.--TW 39, P.T. & T.R.R. Co. Terminal +Station West. East side of 9th Ave. looking North from 31st Street, showing +rock excavation and permanent steel work. March 24, 08.] + +[Illustration: PLATE XLVIII, FIG. 3.--TW 73, P.T. & T.R.R. Co. Terminal +Station West. West side of Ninth Ave. Jacking up girders "C" at Elevated +Railroad Column 491, showing method of taking weight on permanent viaduct +girders. Nov. 14, 08.] + +[Illustration: PLATE XLVIII, FIG. 4.--TW 58, P.T. & T.R.R. Co. Terminal +Station West. East side of Ninth Ave. looking North from 31st St., showing +underpinning of Ninth Ave. Structures. Aug. 10, 08.] + +Fig. 4, Plate XLVII, and Fig. 1, Plate XLVIII, show the structures +supported on the central rock core and the excavation on the east side to +permit of the erection of the permanent viaduct girders. Fig. 1, Plate +XLVIII, shows also the easterly portion of the concrete north abutment. +Fig. 2, Plate XLVIII, shows five rows of the permanent viaduct girders +erected on the east side of the work. + +The excavation of the sides of the avenue having been completed, and six +rows of permanent viaduct girders erected on both sides, timber bents, as +shown on Figs. 2, 4, 5, and 6, were erected on this steel to support the +ends of the girders "C" and carry the structure while the rock core was +being excavated. Fig. 3, Plate XLVIII, shows the method of taking the +weight on these bents. Four 80-ton jacks were used, and oak blocks were +placed on the top of each jack to transmit pressure to a temporary oak cap +under the girders "C" independent of the bents; all four of these jacks +were operated simultaneously, and the girders "C" were lifted off the bents +and clear of the concrete piers. Oak filling pieces were then inserted +between the bents and the girders "C," so that when the jacks were released +the girders "C" were clear of the concrete piers. Fig. 3, Plate XLVIII, +shows that the girders have been lifted off the piers. Elevations were +taken on each set of girders during each operation, and careful +observations were made on the elevated railway columns. Where the rock was +very close to these bents, the open space between the posts was filled with +blocking so that there would be less danger of the bent shifting if struck +by blasted materials. Fig. 3, Plate XLVIII, shows one of these bents filled +with blocking. + +All structures being carried on girders "C," which, in turn, were carried +on the sides of the permanent viaduct, the central core was excavated. Fig. +4, Plate XLVIII, and Figs. 1, 2, 3, and 4, Plate XLIX, show various views +of the work at this stage. + +The central portion of the viaduct was then erected, and, using concrete +piers and timber bents, all structures were placed on its deck. Fig. 3, +Plate XLIX, shows the piers under the elevated railway columns prior to the +removal of girders "C." + +[Illustration: FIG. 6. (Full page image) + +GENERAL ARRANGEMENT OF TEMPORARY AND PERMANENT STRUCTURES] + +During the latter part of 1908 a 48-in. cast-iron water main was laid by +the city on a cradle built by the Railroad Company on girders "C" on the +east side of the avenue. This is part of the high-pressure system, and the +location and elevation of this water main were taken into consideration +when the underpinning was designed. This main, and the 48-in. cast-iron +sewer bracketed to girders "C," are shown on Fig. 4, Plate XLVIII. + +Elevations had been taken on marks on the elevated railway columns +between 30th and 34th Streets at the time the original surveys were made, +in 1902, and these marks were used to test the level of the structure +during the progress of the excavation. + +At the extreme south end of the work the procedure was changed. The east +side was excavated down to sub-grade, the east portion of the south +abutment was constructed, and six rows of the permanent steel viaduct were +erected. Very little excavation had been done on the west side of the +avenue at the south end of the work, and it would have delayed the +completion of the work to have waited for the excavation for and the +construction of the west portion of the south abutment and the erection of +the steel; therefore, instead of supporting the girders "C" on the central +rock core, the east ends were taken up on the permanent viaduct girders, +and the west ends were supported on a concrete pier on the rock. The +central portion of the avenue was excavated in advance of the west portion. +The permanent viaduct girders were put in place from east to west across +the avenue, and the girders "C" were supported on the deck of the permanent +viaduct approximately under the west elevated railway columns before the +west portion of the avenue was excavated, the central portion of the south +abutment having been constructed before the west portion. This procedure +was adopted only at the north girders "C" at elevated railway column No. +488, the south set of girders "C" being on the rock immediately south of +the south abutment. Figs. 2 and 4, Plate XLIX, and Fig. 2, Plate LII, show +various stages of the work at the south end. + +[Illustration: PLATE XLIX, FIG. 1.--TW 60, P.T. & T.R.R. Co. Terminal +Station West. Under Ninth Ave., looking South from North abutment, showing +underpinning and excavation of rock core. Aug. 13, 08.] + +[Illustration: PLATE XLIX, FIG. 2.--TW 84, P.T. & T.R.R. Co. Terminal +Station West. View looking toward Ninth Ave. from South side of 31st St., +200 feet West of Ninth Ave. Jan. 28, 09.] + +[Illustration: PLATE XLIX, FIG. 3.--TW 88, P.T. & T.R.R. Co. N.R. Div. +Terminal Station West. Center line of 32nd St., looking East from Sta. +183+50, showing excavation under Ninth Avenue, permanent concrete piers +under Elevated Railway Columns and removal of temporary shoring girders +"C". April 8, 09.] + +[Illustration: PLATE XLIX, FIG. 4.--TW 95, P.T. & T.R.R. Co. N.R. Div. +Terminal Station West. View under Ninth Avenue looking Southward from 100 +feet South of center line, showing underpinning of Ninth Avenue structure +taken at sub-grade. May 25, 09.] + +It was made a practice all through the work to transfer the weight of the +structures very positively from one support to another by lifting them +bodily by jacks, and putting in filler pieces before releasing the jacks, +not trusting to wedging to transfer the loads. In fact, apart from the +boxing-in of the surface railway concrete, no wedges whatever were used. +This appears to have been a decided advantage, for, with the constant +pounding of trains on the elevated railway and the jarring due to heavy +trucks on the pavement blocks, it is very likely that wedging would have +become loosened and displaced, whereas, with blocking, there was little or +no tendency toward displacement due to vibration. Although the vibration of +the structure, when a long length was supported on girders "C" resting on +the permanent viaduct girders on the sides of the avenue, appeared to be +considerable, not only vertically but transversely, very careful +observation showed that the sag in the girder "C" due a live load of three +elevated railway trains, one surface railway car, and one heavy truck, +amounted to 1/8 in. The sideway vibration did not amount to more than 1/32 +in. on either side of the normal position. More vibration was caused by +heavy trucks and wagons going over the stone pavement than by the elevated +railway trains or surface cars. + +No blasting was done near the supports of the elevated railway structure +while trains were passing over it, and occasionally trains were stopped +during a heavy or uncertain blast. A watchman on the surface, day and +night, and at first one and later two flagmen on the elevated railway +structure, were on duty at all times, reporting to the Interborough Rapid +Transit Company, by whom they were employed. Log mats and timber protection +for the girders and the columns of the permanent viaduct were used, as +shown by Figs. 1 and 4, Plate XLIX, during the excavation of the rock core, +and timber was also used to protect the face of the completed portions of +the concrete abutments. + +In excavating the sides of the avenue, the rock broke better on the east +than on the west side, where large seams developed and some slides +occurred. + +_Abutments._--As shown on Fig. 7, the face of the north abutment has a +batter of 2 in. to the foot, and the face of the south abutment has a +variable batter, the base being on a grade and the bridge seat being level, +and both maintaining a uniform distance from the center of the Terminal +Yard. The back walls of the abutments were not built until the steel had +been put in place. + +No attempt was made to water-proof these abutments, but, in the rear of the +wall, open spaces were left, about 6 ft. from center to center, which were +connected with drain pipes at the base of and extending through the wall, +for the purpose of carrying off any water that might develop in the rock. +These drains were formed by building wooden boxes with the side toward the +rock open and the joints in the boxes and against the rock plastered with +mortar in advance of the wall. A hose was used to run water through these +drains during the placing of the concrete, for the purpose of washing out +any grout which might run into them. Each box was washed out at frequent +intervals, and there was no clogging of the drains whatever. This method +of keeping the drains open was adopted and used successfully for the entire +work. The abutments were built of concrete, and the mixture was 1 part of +cement, 3 parts of sand, and 6 parts of broken stone. + +The concrete was mixed in a No. 3 Ransome mixer, and was placed very wet. +No facing mixture or facing diaphragms were used, but the stone was spaded +away from the face of the wall as the concrete was laid. Chutes were used +inside the form, if the concrete had to drop some distance. Work was +continued day and night, without any intermission, from the time of +commencement to the time of completion of each section. + +The face of the concrete wall was rubbed and finished in a manner similar +to that used on the walls between Ninth and Tenth Avenues, as described +later. + +Fig. 2, Plate LII, shows the east and central portions of the south +abutment, completed and carrying the permanent viaduct, and the excavation +completed for the west portion. + + +WORK BETWEEN NINTH AND TENTH AVENUES. + +_General Description._--The work involved the excavation of about 5.4 +acres, between the west house line of Ninth Avenue and the east house line +of Tenth Avenue, to an average depth of about 50 ft., the construction of a +stone masonry portal at Tenth Avenue leading to the River Tunnels, and the +construction around the site of the concrete retaining and face walls. + +The following estimated quantities appear in the contract: Excavation of +rock in trenches, 3,400 cu. yd.; excavation of rock in pit, 377,000 cu. +yd.; excavation of all materials except rock in trenches, 6,500 cu. yd.; +excavation of all materials except rock in pit, 34,000 cu. yd.; concrete, +1:3:6, in retaining walls, 4,580 cu. yd.; concrete, 1:3:6, in face walls, +7,460 cu. yd.; concrete, 1:2:3, with 3/4-in. stone, in face walls, 4,100 +cu. yd.; stone masonry in portal, 247 cu. yd., etc., etc. + +[Illustration: Fig. 7. (Full page image) + +NINTH AVE. ABUTMENTS & KEY PLAN] + +As previously stated, the contract price included the placing of all +excavated material on scows at Pier 62, North River. Prior to this contract +this pier had been used by the New York Contracting Company-Pennsylvania +Terminal, for the disposal of excavated material from east of Ninth +Avenue. In order to get the material to the pier, the contractor had +excavated a cut under Ninth Avenue which came to the grade of 32d Street +about midway between Ninth and Tenth Avenues, and a trestle was constructed +from this point over Tenth Avenue and thence to the pier. Fig. 2, Plate +XLVII, shows the east end of this cut, and Fig. 1, Plate L, shows the +trestle, looking east from Tenth Avenue. + +A 30-ton steam shovel was brought to the south side of the work, and +commenced operating on July 9th, 1906. After working there about a month, +the earth had been practically stripped off the rock, and the shovel was +moved over to the north side where it excavated both earth and rock until +August 10th, 1907. + +At three points south of 32d Street and at one point north of 32d Street +near Tenth Avenue, cuts were made in the rock to sub-grade, and from these +cuts, together with the cuts on the west side of Ninth Avenue, all widening +out was done and the excavation was completed. Fig. 1, Plate L, shows the +excavation of the three cuts on the south side of 32d Street, the steam +shovel operating on the north side of that street, and the +material-disposal tracks and trestle. Fig. 3, Plate LII, shows the cuts +joined up and the excavation along the south side practically completed. + +On the north side of the work, between Stations 182 + 90 and 183 + 65, the +rock was low, and provision had to be made for maintaining the yards to the +north of the site. Therefore a rubble-masonry retaining wall was built, +with the face about 2 ft. north of the face of the proposed concrete wall +which was to be put in later. On the same side of the work, between +Stations 188 + 24 and 188 + 46, the rock was exceedingly poor, and as a +small frame house on the adjoining lot was considered to be in an unsafe +condition, a rubble masonry retaining wall was built. As the building +adjoining the south side of the work at Tenth Avenue was on an earth +foundation, it was necessary to underpin it before the excavation could be +done. The building was supported on needles, and rubble masonry was put in +from the bottom of the old foundation to the rock. The foundation of 413 +West 31st Street, immediately west of the Express Building site, was of +very poor masonry, and it was necessary to rebuild it prior to taking out +the adjoining excavation. + +[Illustration: PLATE L, FIG. 1.--TW 23, P.N.Y. & L.I.R.R. Terminal Station +West. View looking Eastward from Tenth Ave., showing work between Ninth & +Tenth Avenues. Dec. 26, 06.] + +[Illustration: PLATE L, FIG. 2.--TW 35, P.T. & T.R.R. Co. Terminal Station +West. View looking Northwest from Sta. 184, 120 feet South of center line. +Dec. 31, 07.] + +[Illustration: PLATE L, FIG. 3.--TW 96, P.T. & T.R.R. Co. N.R. Div. +Terminal Station West. View looking West from Ninth Avenue Elevated +Railway, showing condition of work. May 26, 09.] + +[Illustration: PLATE L, FIG. 4.--TW 104, P.N.Y. & L.I.R.R. Terminal Station +West. View from Tenth Avenue looking East, showing progress of concrete +walls. Aug. 7, 09.] + +Along the north side, between Stations 186 + 50 and 187 + 50, the walls +supporting the adjoining back yards were of poor quality and had to be +renewed by the contractor before excavation could be done. + +The excavated material was loaded by derricks on cars at the top of the +excavation, these cars being on tracks having a direct connection with the +disposal trestle, as shown by Fig. 1, Plate L. As soon as it could be done, +derricks were placed at the bottom of the excavation; tracks were then laid +out there, and the excavated material was loaded on cars at the bottom and +hoisted by derricks to cars on the disposal trestle. A locomotive was +lowered to the bottom of the excavation on August 25th, 1907, and a derrick +started operating at the bottom on August 27th, 1907. The commencement of +this work by derricks at the bottom is shown by Fig. 3, Plate LII. In +general, the disposal tracks were maintained about on the center line of +31st Street until the excavation had been carried as close to them as +possible, and on October 16th, 1907, they were shifted to the extreme north +side of the work, as shown by Fig. 2, Plate L. A portion of the old trestle +was left in place near Tenth Avenue, a derrick was erected thereon, and the +tracks were used for cars to receive the excavated material hoisted from +sub-grade. The disposal trestle was maintained in this position until such +time as it would interfere with the excavation, and then the tracks were +abandoned. This was done on November 11th, 1908. Fig. 3, Plate L, shows the +finishing of the excavation on the north side of the work. On August 30th, +1908, a cut was made under Ninth Avenue at sub-grade, and cars could then +be run from Seventh to Tenth Avenue at sub-grade. On October 24th, 1908, +the connection with the disposal trestle east of Ninth Avenue was +abandoned, and all excavated material was hoisted from sub-grade at Tenth +Avenue by derricks. + +As previously stated, the contractor was required to make complete disposal +of all excavated material after January 1st, 1909, but was allowed the use +of the pier until January 20th, 1909, after which date the materials were +hoisted by derricks at Tenth Avenue, loaded on 2-horse trucks, and +transported to the 30th Street pier, North River, where it was loaded on +scows by two electric derricks. A considerable amount of the rock +excavation was broken up and used for back-fill. + +_Earth Excavation._--Practically all the earth excavation, amounting to +about 57,000 cu, yd., was done with steam shovels. The average quantity of +earth excavated by a steam shovel per 10-hour shift was 180 cu. yd. This +material was loaded on side-dump cars and taken to the disposal pier where +it was dumped through chutes to the decks of scows. Inasmuch as the +quantity of earth excavation was small, as compared with the rock, the +earth was used principally for the first layer on the scows for padding, so +that small stones might be dumped through the chutes without injuring the +decks. + +_Rock Excavation._--As previously stated, the rock broke better on the +south than on the north side, where there were several slides, and +considerable excavation had to be taken out beyond the neat line required +in the specifications. The worst slide occurred at midnight on July 3d, +1909, at about Station 188 + 50. The last blast, to complete the excavation +to sub-grade at this point, had been fired in the afternoon of the same +day, and the mucking was practically completed. Great care had been taken +in excavating near this point, as it was evident that the rock was not of a +very stable character, but, when the excavation had been completed, it was +thought that the rock remaining in place would stand. The volume of +material brought down by this slide amounted to about 200 cu. yd. The rock +on the south side broke very well, and there were no slides of any +consequence. + +The drill holes were laid out by the blaster, and the general method of +drilling for different classes of work was as follows: In breaking down, +the holes were started about 8 ft. apart, on a slight batter, so that at +the bottom they would be considerably less than 8 ft. apart. They were +drilled about 10 ft. deep, and blasting logs were used, as it was necessary +to load quite heavily in order to lift the material and start the cut. +After the cut had been made, side holes were shot to widen out sufficiently +to start another cut. + +After a side cut about 20 ft. deep had been made, the side holes were +drilled 20 ft. deep, and the holes were loaded and tamped for the full +20-ft. cut. Under the terms of the specifications, the contractor was +required to complete the excavation on the sides by drilling broaching +holes. + +The maximum length of drill steel was about 20 ft., and, where the +excavation plane of broaching was more than 20 ft. in depth, the contractor +was permitted to start the holes back of the broaching line, in order to +allow for setting up the drills on the second lift. A distance of about 8 +in. was usually allowed for setting up a drill. The broaching line was +painted on the surface of the rock in advance of the drilling, and the +batter of the drill was tested with a specially designed hand-level in +which the bubble came to a central position when the face of the level was +on the required batter. Holes were also drilled in front of this broaching +line, and, when the excavation had been taken out to within about 6 ft. in +front of it, the holes immediately in front were loaded, and also about +every third one of the broaching holes, and, unless the rock was very bad, +it usually broke sharply at the broaching line. Occasionally, the broaching +holes which were not loaded were filled with sand, which gave rather better +results than leaving them open. + +In the steam-shovel work on the east side of Ninth Avenue, spring holes +were used. They were formed by drilling a 20-ft. hole and exploding at the +bottom of it, without tamping, two or three sticks of dynamite, and +repeating this process with heavier charges until there had been formed at +the bottom of the hole a large cavity which would hold from 100 to 200 lb. +of dynamite. Face holes and breast holes were also drilled, and it was +possible by this method to drill and break up a cut 20 ft. deep and 15 ft. +thick. The only place where spring holes were used on this work was on the +east side of Ninth Avenue where the heavy cutting was sometimes extended +beyond the east house line. + +From the best records obtainable, the average progress in drilling was +about 33 lin. ft. per 8-hour shift. The average number of cubic yards of +excavation per drill shift was 13.9, and the average amount of drilling per +cubic yard of excavation was 2.4 ft.; this covered more than 27,000 drill +shifts. + +The dynamite was practically all 60%, and the average excavation per pound +of dynamite was 2.2 cu. yd. The contractor employed an inspector of +batteries and fuses, who, using an instrument for that purpose, tested the +wiring of each blast prior to firing, in order to discover any short +circuits, and thus prevent the danger of leaving unexploded dynamite in the +holes. + +The average quantity of excavation per derrick shift of 10 hours, covering +7,400 shifts, 87% of the excavation being rock, was 50 cu. yd., and the +average force per shift, including only foreman and laborers, was 13 men. +It was found that a derrick operating at the top of a 20-ft. cut would +handle about 40 cu. yd. per shift, whereas, if operating at the bottom of +the cut, it would handle about 60 cu. yd. per shift. The elevator derricks +at Tenth Avenue were very efficient, and each could take care of the +material from four derricks at the bottom, hoisting 250 cu. yd. per shift a +height of 60 ft. + +_Concrete Retaining and Face Walls._--It was essential to have the greatest +space possible at the bottom of the excavation, and, inasmuch as the yard +was to be left open, it was necessary to provide some facing for the rock +on the sides in order to prevent disintegration, due to exposure, and give +a finished appearance to the work. Above the rock surface a retaining wall +of gravity section was designed, the top being slightly higher than the +yards of the adjoining properties. The face wall was designed to be as thin +as possible, in order to allow the maximum space for tracks. + +The excavation, therefore, was laid out so that the back of the retaining +wall would not encroach on the adjoining property, but would practically +coincide with the property line at positions of maximum depth. + +The batter on the face of the wall was 2 in. per ft., and a bridge seat +3-1/2 ft. wide was formed at an elevation of 22 ft., minimum clearance, +above the top of the rail. This bridge seat was made level. The maximum +height of the south wall is 49 ft., and of the north wall 65 ft. + +The face walls were classed as "Upper Face Walls," extending from the base +of the retaining wall to the bridge seat, and as "Lower Face Walls," +extending from the bridge seat to the base of the wall. The general design +is shown on Fig. 8. + +In considering the design of the face wall it was felt that, the wall being +so thin, ample provision should be made to prevent any accumulation of +water and consequent pressure back of the wall; therefore, no attempt was +made to water-proof it, but provision was made to carry off any water which +might appear in the rock. Box drains, 2 ft. wide and 6 ft. from center to +center, were placed against the rock, so that, there being but 4 ft. +between the drains, and the wall having a minimum thickness of 2 ft., any +water in the rock would not have to go more than 2 ft. to reach a drain, +and would probably pass along the face of the rock to a drain rather than +through 2 ft. of concrete. These drains were connected with pipes leading +through the wall at its base. + +[Illustration: FIG. 8. (Full page image) + +RETAINING AND FACE WALLS NORTH SIDE] + +These box drains occurred so frequently, and decreased the section of the +wall so materially, that it was thought desirable to tie the wall to the +rock. This was done by drilling into the rock holes from 6 to 15 ft. in +depth, and grouting into each hole a 1-1/2-in. rod having a split end and a +steel wedge. The outer end of each rod was fitted with a 12 by 12 by +1/2-in. plate and a nut, and extended into the wall, thus tying the +concrete securely to the rock. The drains being 6 ft. from center to +center, the tie-rods were placed midway between them, and 6 ft., from +center to center, vertically and horizontally. Fig. 8 shows the arrangement +of these rods and drains. Around the Express Building site, just west of +Ninth Avenue, on the south side of the work, the bridge seat was omitted, +and the face wall was designed 2 ft. thick from top to bottom. The batter +on the 31st Street wall was made variable, the top and bottom being +constant distances from the center line and on different grades. + +The retaining walls were water-proofed with three layers of felt and +coal-tar pitch, which was protected by 4 in. of brick masonry. A 6-in. +vitrified drain pipe was laid along the back of the wall, with the joints +open on the lower half, and this was covered with 1 ft. of broken stone and +sand before any back-fill was placed on it. + +The arrangement of the drains was as follows: The 6-in. drain back of the +retaining wall was connected with one of the box drains in the rear of the +face wall by a cast-iron pipe or wooden box every 24 ft., and this ran +through the base of the retaining wall. Midway between these pipes, a +connection was made at the bridge seat between the drain in the rear of the +face wall and the gutter formed at the rear of the bridge seat to carry off +rain-water coming down the face of the wall above. All the box drains, +except those connected with the drains back of the retaining wall, were +sealed at the elevation of the base of the retaining wall, as noted +previously. + +The specifications required vitrified pipe to be laid through the retaining +wall, but, owing to the difficulty of holding the short lengths of pipe in +place during the laying of wet concrete, they were dispensed with, and +either iron pipes or wooden boxes were used. + +_Tie-Rods._--When the excavation on the sides had been completed, movable +drilling platforms were erected, as shown by Fig. 4, Plate L. The holes +were drilled on a pitch of 2 in. per ft. with the horizontal. The depths of +the holes were decided by the engineer, and were on the basis of a minimum +depth of 5 ft. in perfect rock; the character of the rock, therefore, and +the presence of seams, determined the depths of the holes. Each hole was +partly filled with grout, and the rod, with the steel wedge in the split +end, was inserted and driven with a sledge so that the wedge, striking the +bottom of the hole first, would cause the split end of the rod to open. +Each hole was then entirely filled with neat cement grout. + +_Box Drains._--Various methods of forming the box drains were considered, +such as using half-tile drains, or a metal form, or a collapsible form +which could be withdrawn, but it was finally decided to build boxes in +which the side toward the rock was open and the joints in the boxes and +against the rock were plastered with cement mortar. These boxes were left +in place. Fig. 1, Plate LI, shows the tie-rods and box drains in place, and +holes being cut near the bottom of the drains for the pipes leading through +the wall. + +_Forms._--Fig. 1, Plate LI, shows the form used on the south side of the +work. The materials were of good quality, and the form, which was about 50 +ft. long, was used to build twelve sections, or about 600 ft. of wall. The +form was tied in at the top and bottom by cables attached to rods drilled +into the rock, and it was thought that, with the trusses to stiffen the +middle section of the form, it would not be necessary to use raker braces +against it. This would have been desirable, as the placing of the raker +braces took considerable time. It was found, however, that the form was not +sufficiently rigid, as it bulged at the middle section and could not be +held by the trusses. Two or three sets of raker braces, about 12 ft. apart, +were used, and in addition, rods with turnbuckles were placed through the +form and fastened to the tie-rods, and thus the form was held in place +successfully. On the forms built later, the trusses were omitted, and raker +braces, about every 6 ft., were used. The rods which screwed into the +turnbuckles were removed before the form was moved. The photograph, Fig. 4, +Plate LII, was taken inside the concrete form for the lower face wall on +the north side, and shows the drains leading through the wall, the +turnbuckles attached to the tie-rods, the cables attached to rods in the +rock, and the braces to keep the form from coming in; these braces, of +course, were removed as the concrete came up. The form was built low and +wedged up into position. After a section of concrete had set sufficiently, +the wedges were knocked out, the form was lowered and moved from the wall, +and was then moved along the lowest waling piece by block and tackle to its +new position. + +Fig. 4, Plate L, shows the forms used on the north side of the work. + +A section, 1 ft. square, at the top of the bridge seat of the lower face +wall, was left out, so that the bottom of the form for the upper face wall +could be braced against it. The top of this form was tied by cables +attached to rods in the rock and by rods with turnbuckles running from back +to front of the form; braces were also put in from the back of the +retaining wall form to the walls of buildings along the property lines, +when this could be done. The middle section of the form was held by rods +with turnbuckles which passed through the form and were fastened to each of +the tie-rods drilled into the rock, as was also done in the case of the +lower face wall. It was generally possible to hold the form to true +position in this manner, but occasionally it had a tendency to bulge; when +this occurred, the rods leading through the form and fastened to the +tie-rods were tightened up, the placing of the concrete was slowed up, and +no serious bulging occurred. + +Bulkheads at the ends of the sections were built of rough planking securely +braced to the rock, except that a planed board was laid up against the face +of the form to make a straight joint. At the end of each section a V was +formed, as shown by Fig. 1, Plate LI. At all corners, a "return," or +portion of the wall running at right angles, was built, and no section of +wall was stopped at a corner. + +_Filling Forms of Lower Face Walls._--A temporary trestle was erected above +the elevation of the bridge seat, and a track, leading from the mixer to +the form to be filled, was laid on it. At the commencement of each section +a layer of mortar (1 part of cement to 2-1/2 parts of sand) was deposited +on the bottom. A 1:3:6 mixture of concrete was used; it was run from the +mixer into dump-cars and deposited in the form through chutes, three of +which were provided for each 50-ft. section, the average length. The +concrete was mixed wet, and was not rammed; the stone was spaded back from +the face, and no facing mixture or facing diaphragms were used. Work on +each section was continued day and night without any intermission from the +time of commencement to the time of completion. At frequent intervals the +box drains were washed out thoroughly with a hose, in order to prevent them +from clogging up with grout. + +[Illustration: PLATE LI, FIG. 1.--TW 66, P.N.Y. & L.I.R.R. Terminal Station +West. Box drains and tie rods, South side, Sta. 184+80 to 185+14. Sept. 17, +08.] + +[Illustration: PLATE LI, FIG. 2.] + +[Illustration: PLATE LI, FIG. 3.--P 46. P.R.R. Tunnels, N.R. Div. Sect. Gy. +West. Disposal trestle just before demolition. View of South side showing +chutes. Jan. 21, 09.] + +[Illustration: PLATE LI, FIG. 4.--A 54. P.R.R. Tunnels, N.R. Div. Sect. Gy. +West & Oj. View across North River on line of Tunnels, looking from New +York to New Jersey. Feb. 9, 07.] + +In the first few sections of wall, the form was filled to within 1 in. of +the top of the bridge seat and allowed to set for about 2 hours; it was +then finished to the proper elevation with a plaster of 1 part of cement to +1 part of sand. This did not prove satisfactory, as there were indications +of checking and cracking, and, later, the form was filled to the required +elevation and the surface floated. The form was allowed to remain in place +for from 18 to 24 hours, depending on the weather. In most cases, +immediately after the form had been moved, a scaffold was erected against +the face of the wall, and the face was wet and thoroughly rubbed, first +with a wooden float and then with a cement brick, until the surface was +smooth and uniform. + +The section 1 ft. square at the top of the bridge seat, which was left out +in order to brace the bottom of the form for the upper face wall, was +filled in after the walls had been completed. The old concrete was very +thoroughly cleaned before the new concrete was placed on it, and a gutter +was formed at the rear connecting with the box drains back of the wall to +carry off rain-water coming down the face of the upper walls. + +In hot weather the walls were thoroughly wetted down several times a day +for several days after the form had been removed. + +_Upper Face and Retaining Wall._--In cases where the top of the retaining +wall was at a higher elevation than the mixer, it was necessary to raise +the concrete in a bucket with a derrick, and dump it into cars on the +trestle above the top of the coping. Concrete was deposited through chutes, +as in the lower face wall, continuously from the bottom of the face wall to +the top of the retaining wall. At the commencement of each section of the +retaining wall a layer of mortar was put on the rock. A 1:2:3 mixture of +concrete was used in the face wall, and a 1:3:6 mixture in the retaining +wall. + +As the face walls were so thin, the number of batches of concrete per hour +was reduced, for the form filled so rapidly that the concrete, before it +set, exerted an excessive pressure against the form, and this tended to +make it bulge. The proper rate at which to place the concrete behind a form +50 ft. long, with a wall 2 ft. thick, was found to be about fifteen 1/2-yd. +batches per hour. + +_Cracks in Walls and Longitudinal Reinforcement._--Before the concrete +walls were started, the contractor suggested using forms 100 ft. long and +building the walls in sections of that length; it was decided, however, to +limit the length to 50 ft. + +The south walls, in sections approximately 50 ft. long, were built first, +starting at Tenth Avenue and extending for about 500 ft. Soon after the +forms were removed, irregular cracks appeared in the walls between the +joints in practically every section. It was thought that these cracks might +be due to the wall being very thin and being held at the back by the +tie-rods; there was also quite a material change in the section of the wall +at each drainage box. Although it was admitted that these cracks would have +no effect on the stability of the wall, it was thought that, for appearance +sake, it would be desirable to prevent or control them, if possible. The +first method suggested was to shorten the sections to 25 ft., which would +give an expansion and contraction joint every 25 ft., it being thought that +sections of this length would not crack between the joints. This, however, +was not considered desirable. An effort was then made to prevent cracks in +a section of wall, about 46 ft. long, on the south side, by using +longitudinal reinforcement. In the lower and upper face walls, 3/4-in. +square twisted steel rods were placed longitudinally about 4 in. in from +the face and about 1 ft. 4 in. apart vertically. The sections of these +walls were finished on April 10th, and May 5th, 1909, respectively. At +present there are no indications of cracks in these sections, and they are +practically the only ones in the south walls which do not show irregular +cracks. + +It was decided, however, that, inasmuch as the cracks did not affect the +stability of the walls, the increased cost of thus reinforcing the +remaining walls was not warranted. An effort to control the cracks was made +by placing corrugated-iron diaphragms in the form, dividing each 50-ft. +section into three parts. The diaphragms were 1 ft. wide, and were placed +with the outer edge 1 in. in from the face of the wall, but in the copings +they were omitted. The purpose of these diaphragms was to provide weak +sections in the walls, so that if there was any tendency to crack it would +occur along the line of the diaphragms. Corrugated iron was used for the +diaphragms instead of sheet iron as it was more easily maintained in a +vertical position. The general arrangement of the diaphragms is shown on +Fig. 4, Plate LII. The results obtained by using diaphragms have been quite +satisfactory, and cracks approximately straight and vertical have usually +appeared opposite the diaphragms soon after the forms were removed. +Diaphragms were used on all the remaining walls, with the exception of +those between Stations 187 + 07 and 188 + 83 on the north side, where the +rock was of poor character and bad slides had occurred. Between these +points, in order to strengthen the wall, twisted steel rods, 1 in. square, +were placed longitudinally, 6 in. in from the face of the wall and 2 ft. +apart vertically, between Elevations 295 and 335. + +[Illustration: PLATE LII, FIG. 1.--GIRDERS UNDER 9TH AVENUE ELEVATED +RAILROAD.] + +[Illustration: PLATE LII, FIG. 2.--TW 100. P.T. & T.R.R. Co. Terminal +Station West. Showing excavation of completion of South abutment 9th Ave. +and method of Supporting Elevated Railway Column 488. July 21, 09.] + +[Illustration: PLATE LII, FIG. 3.--TW 31. P.T. & T.R.R. Co. Terminal +Station West. View showing excavation 9th and 10th Avenues South of 32nd +St. looking West from Sta. 184. Aug. 17, 07.] + +[Illustration: PLATE LII, FIG. 4.--TW 101. P.T. & T.R.R. Co. Terminal +Station West. Inside of concrete form for lower-face wall, showing drains, +tie rods, diaphragms and methods employed for tying in the form in addition +to braces outside. July 21, 09.] + +_Tenth Avenue Portal._--The design of the Tenth Avenue Portal is shown on +Fig. 9. The stone selected came from the Millstone Granite Company's +Quarries, Millstone Point, Conn., and is a close-grained granite. Fig. 2, +Plate LI, shows the completed portal. + +Practically all the stone cutting was done at the quarry, but certain +stones in each course were sent long and were cut on the ground, in order +to make proper closures. Drains were left behind the portal around the back +of each arch, leading down to the bottom, and through the concrete base at +each side of the portal and in the central core-wall; all these drains have +been discharging water. + +_Power-House._--The old church at No. 236 West 34th Street, between Seventh +and Eighth Avenues, was turned over to the New York Contracting +Company-Pennsylvania Terminal for a power-house to supply compressed air +for use on the Terminal Station work between Seventh and Ninth Avenues and +the work below sub-grade as well as that on the Terminal Station-West. Four +straight-line compressors and one cross-compound Corliss compressor were +installed, the steam being supplied by three Stirling boilers. Three +electrically-driven air compressors, using current at 6,600 volts, were +also installed, and the total capacity of the power-house was about 19,000 +cu. ft. of free air per minute compressed to 90 lb. per sq. in. + +_Disposal Pier._--The disposal pier (old No. 62 and new No. 72), at the +foot of West 32d Street, North River, was leased by the Pennsylvania +Railroad Company. The entire pier, with the exception of the piles, was +taken down, and the piles which would be in the path of the proposed tunnel +were withdrawn prior to the building of the tunnels and the construction of +the pier for disposal purposes. Subsequent to the driving of the tunnels +there was a considerable settlement in the pier, especially noticeable at +the telphers, and finally these had to be abandoned on this account. Fig. +3, Plate LI, shows the chutes through which the earth was dumped on the +decks of the scows to form a padding on which to dump the heavier rock. +Fig. 4, Plate LI, shows the derricks at the end of the pier. These were +used, not only for loading heavy stones and skips, but also with a +clam-shell bucket for bringing in broken stone and sand for use in the +work. Large quantities of pipe, conduits, brick, etc., were also brought to +this pier for use on the work. + +[Illustration: FIG. 9. (Full page image) + +PORTAL, RETAINING AND FACE WALLS, TENTH AVENUE] + + +ORGANIZATION OF ENGINEERING FORCE IN FIELD. + +The design and execution of the work were 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 writer acted as Resident Engineer. + +[Illustration: Fig. 10.] + +The general organization of the engineering force in the field is shown by +the diagram, Fig. 10. + +The position of Assistant Engineer, in responsible charge of Construction +and Records, has been filled in turn by Messrs. A.W. Gill, N.C. McNeil, +Jun. Am. Soc. C.E., and W.S. Greene, Assoc. M. Am. Soc. C.E. + +Messrs. A.P. Combes and T.B. Brogan have acted as Chief Inspector and Night +Inspector, respectively, in charge of outside work during the entire +carrying out of the contract. + +Base lines had been established on Ninth and Tenth Avenues for the Terminal +work east of Ninth Avenue and for the Tunnel work west of Tenth Avenue, +and these lines, together with bench-marks similarly established, were used +in laying out the Terminal Station-West work. + +Prior to the commencement of the work, elevations were taken on the surface +at 10-ft. intervals, and elevations of the rock surface were taken on these +points as the rock was uncovered. Cross-sections were made and used in +computing the progress and final estimates. + +Very careful records were kept of labor, materials, derrick performances, +steam-shovel performances, quantity of dynamite used, etc., and, in +addition, a diary was kept giving a description of the work and materials +used each day; various tables and diagrams were also prepared. + +A daily report was sent to the Chief Office showing the quantities of +excavation removed and concrete built, the force in the field, the plant at +work, etc., during the previous day. At the end of each month a description +of the work done during that month, with quantities, force of men employed, +percentages of work done, etc., was sent to the Chief Office. Two diagrams, +showing cross-sections and contours of the excavation done and the progress +of the concrete walls, were also sent. + + +COST ACCOUNT. + +From the records of labor and material obtained in the field, and from +estimated charges for administration and power, an estimate was made of the +cost to the contractor for doing various classes of work. It was necessary +to estimate the administration and power charges, as the contractor's +organization and power-house were also controlling and supplying power to +the Terminal Station work east of Ninth Avenue and also the work below +sub-grade. The labor and material charges in the field were placed directly +against the class of work on which they were used and the administration +and general charges (which included superintendence, lighting, etc.) were +apportioned to the various classes of work in proportion to the value of +the labor done. + + +STATISTICS. + +The total weight of the structural steel used during the underpinning of +Ninth Avenue was 1,475,000 lb. + +The total weight supported during the work under Ninth Avenue was about +5,000 tons. + +\U$1\EThe average daily traffic over the Ninth Avenue Elevated Railway was +90,000 passengers, and, during the progress of the excavation and +underpinning, about 100,000,000 passengers were carried over that +structure. + +The total excavation was 521,000 cu. yd., of which 87% was solid rock. + +The average drill performance was about 33 lin. ft. per 8-hour shift. + +The average number of cubic yards of excavation per drill shift was 13.9. + +The average number of feet of drilling per cubic yard of excavation was +about 2.4. + +The average excavation per pound of dynamite was 2.2 cu. yd. + +The average amount of excavation per derrick shift of ten hours, 87% of the +excavation being rock, was 50 cu. yd. + +The average derrick force per shift, including only foreman and laborers, +was 13 men. + +The salaries of the engineering staff in the field and the expenses of +equipping and maintaining the field office amounted to 2.8% of the cost of +the work executed, 2.7% being for engineering salaries alone. + +FOOTNOTES: + +[Footnote A: Presented at the meeting of April 6th, 1910.] + + + + + +End of the Project Gutenberg EBook of Transactions of the American Society +of Civil Engineers, vol. 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