,,american ,,society ,,of ,,civil ,,engineers ,,instituted #aheb ,,transactions ,paper ,no4 #aaeh ,,the ,,new ,,york ,,tunnel ,,extension ,,of ,,the ,,pennsylvania ,,railroad4 ,,the ,,cross-,,town ,,tunnels4,a ,,by ,,james ,h4 ,,brace ,,and ,,francis ,,mason1 ,,members1 ,,am4 ,,soc4 ,c4 ,e4 ,in this paper1 it is proposed to describe the construction of the tunnels extending eastward from the easterly extension of the ,terminal ,station to the permanent shafts east of ,first ,avenue4 ,they were located under #cb;d and #cc;d ,streets from the station to ,second ,avenue1 and thence1 curving to the left1 passed under private property and ,first ,avenue to the shafts1 as described in a preceding paper4 ,typical cross-sections of the tunnels are shown on ,plate ,,xii4,b ,on ,may #bith1 #aije1 a contract was entered into with the ,united ,engineering and ,contracting ,company for the performance of this work4 ,this contract provided that work on each pair of tunnels should be carried on from two shafts4 ,the first1 here referred to as the ,first ,avenue ,shafts1 were located just east of that avenue and directly over the line of the tunnels2 the other two1 called the ,intermediate ,shafts1 were located on private property to the north of each pair of tunnels in the blocks between ,fourth and ,madison ,avenues4 ,it was originally intended to do all the work of construction from these four shafts4 ,workings were started both east and west from the ,intermediate ,shafts1 and those to the west were to be continued to the ,terminal ,station4 ,after the change of plans1 described in a previous paper1 it was decided to sink a third shaft on each line4 ,these were known as the ,west ,shafts1 and were located between ,sixth and ,seventh ,avenues4 ,finally1 it was found necessary to build a portion of the tunnels on each line west of ,sixth ,avenue in open cut4 ,the locations of the shafts are shown on ,plate ,,xiv4,c ,the ,first ,avenue shafts were built by ,s4 ,pearson and ,son1 ,inc41 for the joint use of the two contractors1 as described in the paper on the tunnels under the ,east ,river4 ,while the shafts were being sunk1 the full-sized tunnels were excavated westward by the contractor for the river tunnels for a distance of #ej ft41 and top headings for #ej ft4 farther4 ,by this means1 injury to the caissons and to the contractor's plant in the shafts by the subsequent work in the ,cross-,town ,tunnels was avoided4 ,the west half of the shaft was for the exclusive use of the contractor for the ,cross-,town ,tunnels4 ,,contractor',s ,,plant4 ,the method of handling the work adopted by the contractor was1 broadly speaking1 as follows3 ,excavation was usually carried on by modifications of the top-heading and bench method1 the bench being carried as close to the face as possible in order to allow the muck from the heading to be blasted over the bench into the full section4 ,the spoil was loaded into #c-yd4 buckets 7designed by the contractor and hereinafter described71 by steam shovels operated by compressed air1 and hauled to the shafts by electric locomotives4 ,electrically-operated telphers1 suspended from a timber trestle1 hoisted the buckets1 and1 traveling on a mono-rail track1 deposited them on wagons for transportation to the dock4 ,arriving at the dock1 the buckets were lifted by electrically-operated stiff-leg derricks and their contents deposited on scows for final disposal4 ,the spoil was thus transported from the heading to the scow without breaking bulk4 ,when concreting was in progress1 the spoil buckets were returned to the shafts loaded with sand and stone4 ,the concrete materials were deposited in storage bins placed in the shafts1 from which they were fed to the mixers located at the foot of the shaft about on a level with the crown of the tunnels4 ,the concrete was transported to the forms in side-dump1 steel1 concrete cars1 hauled by the electric locomotives4 ,electrical power was adopted largely on account of the restricted area at the shaft sites1 where a steam plant would have occupied considerable space of great value for other purposes4 ,the installation of a steam plant at the ,intermediate ,shafts1 which were located in a high-class residential district1 would have been highly objectionable to the neighboring property owners1 on account of the attendant noise1 smoke1 and dirt1 and1 in addition1 the cost of the transportation of fuel would have been a serious burden4 ,except for the forges and1 toward the last1 the steam locomotives1 not a pound of coal was burned on the work4 ,the use of the bucket and telpher also eliminated most of the objectionable noise incident to the transfer of spoil from tunnel cars to ordinary wagons at the shaft sites4 ,power plants were installed at the ,north ,shaft near ,first ,avenue and at the rear of the #cc;d ,street ,intermediate ,shaft4 ,first ,avenue ,plant4--,fig4 #a1 ,plate ,,lviii1 is a general view of the ,first ,avenue plant4 ,the power-house at the corner of #cdth ,street and ,first ,avenue supplied compressed air for operating drills1 shovels1 pumps1 and hoists in the tunnels driven from the river shafts1 and in it three ,laidlaw-,dunn-,gordon compressors were installed4 ,the largest was a #cb by #bj by #cj-;in41 two-stage1 cross-compound1 direct-connected to a ,fort ,wayne #dhj h4p41 #bcj-volt1 direct-current1 constant-speed motor run at #ajj rev4 per min4 ,this compressor was rated at #b1hgj cu4 ft4 of free air per minute at a pressure of #ajj lb4 ,it was governed by throttling the suction1 the governor being controlled by the pressure in the air receiver and the motor running continuously at a constant speed4 ,the two others were of similar type1 one was #bb-a_/b by #ad by #ah-;in41 rated at #a1bej cu4 ft4 of free air at a pressure of #ajj lb41 the other was #af by #aj by #ah-;in41 rated at #fcj cu4 ft4 ,they were fitted with #i-;ft4 fly-wheels1 and were driven at #aej rev4 per min4 by #aje-;h4p41 ,general ,electric1 #bbj-volt1 compound-wound1 direct-current motors running at #fee rev4 per min4 ,the larger of these two compressors was driven by two of the motors belted in tandem1 and the smaller was belt-connected to a third motor4 ,the compressors were water-jacketed and had small inter-coolers1 the water supply for which was itself cooled in a ,wheeler ,condenser and ,engineering ,company's water-cooling tower4 ,the pump and the blower operating it were electrically driven4 ,the telphers1 used for hoisting muck from the tunnels and for lowering supplies1 were each hung from single rails on a timber trestle1 about #dj ft4 high1 spanning and connecting the two shafts4 ,one machine was provided for each shaft1 and where their tracks crossed #cc;d ,street they were separated sufficiently to permit the machines to pass each other4 ,at this point1 and covering the street1 a large platform was provided1 on which the trucks were loaded and unloaded 7,fig4 #b1 ,plate ,,lviii71 and from which they descended by an incline on ,first ,avenue leading south to #cb;d ,street4 ,the platform also covered practically all the yard at the ,south ,shaft and materially increased the available working area4 ,the telphers were built by the ,dodge ,cold ,storage ,company1 and were operated by a #ge-;h4p4 ,general ,electric motor for hoisting and a #ae-;h4p4 ,northern ,electric ,company motor for propulsion4 ,their rated lifting capacity was #aj1jjj lb4 at a speed of #bjj ft4 per min4 ,the carpenter shop and machine-shop1 both of which served the entire work1 were conveniently located in small buildings on the loading platform4 ,in the former the saws were each run independently by small electric motors suspended under the platform4 ,the heavy forms and form carriages used in lining the tunnels with concrete were fabricated and stored on the platform outside4 ,the machine-shop lathes1 etc41 were all belted to one shaft driven by an #h-;h4p4 ,general ,electric motor4 ,above the machine-shop was a locker-room and below it on the street level was the main blacksmith shop for the work4 ,subsidiary blacksmith shops were located at each of the other shafts4 ,the storeroom and additional locker-rooms were located above the power-plant in the ,north ,shaft yard1 and isolated from the other structures was a small oil-house4 ,additional storage space was provided by the contractor on #cb;d ,street just west of ,first ,avenue by renting three old buildings and the yards in the rear of them and of the ,railroad ,company's cement warehouse adjacent4 ,here electric conduits1 pipe1 castings1 and other heavy and bulky supplies were stored4 ,during excavation the headings were supplied with forced ventilation through #ab-;in4 and #ad-;in4 ,no4 #af1 spiral-riveted1 asphalted pressure pipes1 canvas extensions being used beyond the ends of the pipes4 ,a ,no4 #d ,american ,blower1 located at the top of each shaft and driven by a #ae-;h4p4 ,general ,electric motor1 supplied the air4 ,illustration3 ,,plate ,,lviii1 ,,fig4 #a4--,,view ,,of ,,first ,,avenue ,,plant4 ,illustration3 ,,plate ,,lviii1 ,,fig4 #b4--,,telpher ,,structure ,,and ,,loading ,,platform1 ,,first ,,avenue ,,shaft4 ,illustration3 ,,plate ,,lviii1 ,,fig4 #c4--;,,headworks ,,at #cc;,d ,,street3 ,,intermediate ,,shaft4 ,illustration3 ,,plate ,,lviii1 ,,fig4 #d4--,,loading ,,spoil ,,on ,,barges1 #ce,,th ,,street ,,pier4 ,a concrete-mixing plant was placed in each shaft1 the mixer being located high enough to discharge into cars at about the level of the springing line of the arch4 ,above the mixers were the measuring hoppers set in the floor of a platform which was large enough to carry half a day's supply of cement4 ,at the ,south ,shaft the cement was delivered to this floor from the loading platform through a spiral steel chute2 at the ,north ,shaft it was lowered in buckets by the telpher4 ,the sand and stone were drawn into the hoppers through short chutes from the base of the storage bins which occupied the remaining height of the shaft--about #ej ft4 ,at the ,south ,shaft the bins were of concrete and steel1 about #f by #ab ft4 in section1 and attached to the central wall of the caisson4 ,sand and stone were delivered into them from dump-wagons on the loading platform4 ,at the ,north ,shaft steel-plate bins were used1 and were supplied with material by the buckets handled by the telpher4 ,the mixers were ,no4 #e ,smith1 belt-connected to #be-;h4p4 motors1 and about #j4h cu4 yd4 of concrete was mixed at a batch4 ,the concrete cars were steel side-dumpers of the ,wiener or ,koppel type4 ,in order to be able to continue concreting during the winter1 when neither sand nor stone could be obtained by water1 practically all the space under the loading platforms in the ,south ,shaft yards not occupied by the blacksmith shop was filled with these materials1 which were placed in storage in the late fall4 ,intermediate-,shaft ,plant4--,the air-compressing plant was located at the rear of the #cc;d ,street ,intermediate ,shaft1 and supplied air for driving the tunnels east and west from the ,intermediate ,shafts on both #cb;d and #cc;d ,streets4 ,two compressors1 the same as the large ,laidlaw-,dunn-,gordon machine at ,first ,avenue1 were installed here1 with a similar water-cooling tower4 ,both shafts were on private property1 owned by the ,railroad ,company1 on the north side of the streets1 and each was equipped with two telphers supported on timber trestles1 similar to those at ,first ,avenue4 ,here1 however1 the buckets were placed on wagons standing at the curb1 as shown by ,fig4 #c1 ,plate ,,lviii4 ,blowers for ventilation were installed at each shaft1 as at ,first ,avenue1 and1 after the excavation had proceeded some distance1 small blacksmith shops1 for sharpening drill steel and making minor repairs1 were located in the tunnels near the shafts4 ,the concrete plant in each shaft was similar in arrangement to those at ,first ,avenue1 but the storage bins had wooden walls made of #b by #d-;in4 and #b by #f-;in4 scantling nailed flat on each other4 ,the contractor's office on #cc;d ,street backed up against the #cb;d ,street shaft site1 and the basement was used as a storeroom for supplies for both shafts4 ,after the decision to do part of the work between ,sixth and ,seventh ,avenues in open cut1 an #h-;in4 air main was laid in #cc;d ,street to the ,west ,shafts1 and air was supplied from the ,intermediate ,shaft for work on both streets in that neighborhood4 ,west-,shaft ,plant4--,west of ,sixth ,avenue1 between #cb;d and #cc;d ,streets and adjacent to the open-cut sections1 the ,railroad ,company obtained from the ,hudson and ,manhattan ,railroad ,company the use of a large area from which the buildings had recently been removed1 and gave the use of it to the contractor4 ,this was of great value in prosecuting the west end of the work4 ,the two ,west ,shafts were located in the streets and were supplied with short timber trestles similar to those at the ,intermediate ,shafts4 ,one telpher was taken from each of the ,intermediate ,shafts to operate at each of the ,west ,shafts4 ,in addition1 a number of stiff-leg derricks were set up along the open-cut section1 and were operated by ,lidgerwood or ,lambert air hoisting engines1 or by electric motors1 as circumstances dictated4 ,a #ae-ton ,bay ,city locomotive crane was also used along part of the open-cut work on #cb;d ,street4 ,several concrete plants were installed at points along the open-cut section1 and were moved from place to place1 the same general arrangement being adopted as at the plants already described4 ,no4 #c and ,no4 #d ,ransome mixers were used1 and were generally set up at about the level of the top of the arch4 ,the sand and stone storage bins were made of scantlings spiked together1 and were necessarily rather shallow on account of the proximity of the tunnels to the street surface4 ,thirty-fifth ,street ,pier4--,for the receipt and disposal of materials at the #ceth ,street pier1 four stiff-leg derricks1 operated by electric hoisting engines1 were installed4 ,two were used in lifting the muck buckets from the wagons and dumping their contents on the scows for final disposal 7,fig4 #d1 ,plate ,,lviii72 and the other two were fitted with clam-shell buckets for unloading sand and broken stone from barges and depositing the materials in large hoppers1 from which they were drawn into wagons for transportation to the various concrete plants4 ,a large part of the cement 7all of which was supplied by the ,railroad ,company7 was also unloaded at the #ceth ,street pier and hauled directly to the work1 the surplus being stored temporarily in the ,company's cement warehouses on #cb;d1 #cc;d and #ceth ,streets1 near ,first ,avenue1 from which it was drawn as required4 ,on the dock was located the main powder magazine1 a small concrete structure4 ,considerable use was also made of neighboring piers for unloading electric conduits1 lumber1 steel1 etc4 ,illustration3 ,,fig4 #a4 ,,special ,,steel ,,bucket ,,plan ,,of ,,bucket ,,end ,,view ,,side ,,view ,,of ,,bucket ,,section ,,at ,a-,a ,tunnel ,plant4--,the spoil buckets1 designed by ,d4 ,l4 ,hough and ,george ,perrine1 ,members1 ,am4 ,soc4 ,c4 ,e41 were a novel feature of the work4 ,these buckets are shown in detail in ,fig4 #a and various photographs4 ,they were of #c cu4 yd4 capacity and were split longitudinally1 the two halves being pinned at the apices of the ends4 ,for lifting1 they were suspended from eyes at that point1 and1 when dumping1 trip ropes were hooked into eyes at the bottom of each side2 lifting the trip ropes or lowering the hoisting rope split the bucket1 as shown in ,fig4 #d1 ,plate ,,lviii1 and dumped the contents4 ,they were transported in the tunnel on flat cars1 and in the street on wagons1 both cars and wagons being provided with cradles shaped to receive the bottom of the bucket4 ,in the tunnels the loading was done with air-operated steam shovels1 four 7,model #bj7 ,marion shovels being used at various points of the work4 ,in ,fig4 #a1 ,plate ,,lix1 one of these is shown loading the bucket4 ,the cars were hauled by ,general ,electric1 standard1 #aj-ton1 mine locomotives1 the current for which was taken at #bbj volts from a pair of ,no4 #jj copper trolley wires suspended from the roof of the tunnel4 ,the collector was a small four-wheeled buggy riding on the wires and connected to the locomotive by several hundred feet of cable wound on a reel for use beyond the end of the trolley wire4 ,two #h-a_/b-ton1 ,davenport1 steam locomotives were also used in #cb;d ,street1 toward the end of the work1 after the headings had been holed through and the tunnels would quickly clear themselves of gas and smoke4 ,the steam shovels were supplemented by two ,browning1 #ae-ton1 locomotive cranes1 which handled the spoil in places where timbering interfered with the operation of the shovels4 ,all tracks were of #c-;ft4 gauge throughout and laid with #dj-lb4 rails4 ,practically all the heavy drilling was done with ,ingersoll drills 7,model ,e #eb71 the trimming being largely done with jap and baby drills4 ,a large number of pumps were used at various points on the work1 and practically all were of ,cameron make1 the largest ones at the shaft being #aj by #e by #ac-;in4 ,the grout machines were of the vertical-cylinder1 air-stirring type4 ,,shaft ,,sinking4 ,the sinking of the ,intermediate ,shafts was the first work undertaken by the contractor4 ,the #cc;d ,street ,shaft was #cd4e ft4 long1 #ba ft4 wide1 and #hc ft4 deep4 ,the rock surface averaged #e ft4 below the ground surface4 ,sinking was started on ,july #ajth1 #aije1 and was completed on ,october #c;d1 #aije1 the rock being hard and dry4 ,the average daily rate was #j4gc ft4 and an average of #ag4a cu4 yd4 were excavated per day1 with two shifts of #h hr4 each4 ,the first shift started at #f ,a4 ,m4 and the second at #b4cj ,p4 ,m41 ending at #aa ,p4 ,m4 ,these hours were adopted in order to avoid undue disturbance during the night4 ,illustration3 ,,plate ,,lix1 ,,fig4 #a4--;,,air-,,operated ,,steam ,,shovel ,,used ,,in ,,tunnel4 ,illustration3 ,,plate ,,lix1 ,,fig4 #b4--,,timbering ,,in ,,top ,,headings ,,above ,i-,,beams4 ,illustration3 ,,plate ,,lix1 ,,fig4 #c4--;,,first ,,section ,,of ,,concrete ,,lining ,,at ,,fifth ,,avenue4 ,illustration3 ,,plate ,,lix1 ,,fig4 #d4--,,timbering ,,and ,,rubble ,,masonry ,,over ,i-,,beams4 ,before blasting the first lift of rock1 channel cuts #e or #f ft4 deep were made along the sides of the shaft1 in order to avoid damage to the walls of neighboring buildings4 ,timbering was required for a depth of only #aj ft4 below the surface of the ground4 ,a drift1 #cj4f ft4 long1 #ag ft4 wide1 and #bg ft4 high1 connected the south end of the shaft with the tunnels4 ,the drift was excavated in three stages1 a top heading and a bench in two lifts4 ,while blasting the cut in the top heading1 there was enough concussion to break glass in the neighboring buildings4 ,the use of a radialax machine reduced the concussion somewhat1 but it was very quickly abandoned on account of the length of time required for the drilling4 ,the construction of the #cb;d ,street ,shaft was quite similar to the one on #cc;d ,street4 ,it was #ca4e ft4 long1 #bj4e ft4 wide1 and #ga ft4 deep4 ,the depth of earth excavation averaged #ai4e ft4 ,the rock in this shaft was seamy and not quite as hard or dry as that in #cc;d ,street1 and timbering was required for practically the full depth to the crown of the drift4 ,sinking was started on ,may #aeth1 #aije1 and was completed on ,october #bfth1 #aije4 ,the daily average rate was #j4cj ft4 in earth and #j4eb ft4 in rock4 ,the drift was excavated in much the same manner as the one in #cc;d ,street1 but the rock being softer the radialax machine was not used4 ,,tunnel ,,excavation4 ,during the early part of the work1 the contractor devoted his entire attention to the work of excavation4 ,nearly all the excavation east of ,fifth ,avenue was done before any of the lining was placed4 ,at a number of points west of ,fifth ,avenue and at a few points to the east the nature of the rock was such that the two operations had to be done simultaneously4 ,single-,tunnel ,method4--,for an average distance of #cej ft4 west from the ,first ,avenue ,shafts there were four single tunnels4 ,the rock was sound and comparatively dry4 ,a top heading of the full size of the tunnel and about #h ft4 high was first driven4 ,it was drilled by four drills mounted on two columns1 and was blasted in the ordinary way4 ,the bench was about #ac ft4 high4 ,tripod drills1 standing on the bench1 drilled the usual holes1 but1 owing to the lack of head-room1 steels long enough to reach the bottom of the bench could not be used4 ,tripod drills were set as low as possible at the foot of the bench and drilled lifting holes4 ,these holes were inclined downward from #aj to #ae to the horizontal1 and were spaced to converge at the location of the drainage ditches4 ,the heading was usually driven from #aj to #bj ft4 in advance of the bench4 ,at this distance a large part of the muck from the heading was shot backward over the bench4 ,in the single tunnels the muck was loaded by hand4 ,twin-,tunnel ,methods4--,from the end of the single-track tunnel westward to ,fifth ,avenue on #cc;d ,street1 and to ,madison ,avenue on #cb;d ,street1 with some exceptions1 each pair of tunnels was excavated for the entire width at one operation4 ,three different methods of work were extensively used4 ,they were the double-heading method1 the center-heading method1 and the full-sized-heading method1 and these differed only in the manner of drilling and blasting4 ,the bench was usually within #aj or #ae ft4 of the face of the heading1 and was drilled and fired in the same way as in the single tunnels4 ,after the installation of the permanent plant1 most of the muck was handled by steam shovels4 ,in the double-heading method1 shown on ,plate ,,lvii1 the top headings for each tunnel of the pair were driven separately1 leaving a short rock core-wall between them4 ,the headings were drilled from columns in the manner described for the single tunnels4 ,the temporary rock dividing wall between the headings was drilled by a tripod drill on the bench of one of the headings1 and was fired with the bench4 ,in the center-heading method1 also shown on ,plate ,,lvii1 only one heading was driven4 ,it was rectangular in shape1 about #h ft4 high and #ad ft4 wide4 ,it was located on the center line between the tunnels4 ,in general1 the face was from #f to #ab ft41 or the length of one or two rounds1 in advance of the remainder of the face at the top4 ,the center heading was drilled by four drills mounted on two columns4 ,by turning these drills to the side1 they were used for holes at right angles to the line of the tunnels1 by which the remainder of the face of the heading was blasted4 ,by turning the drills downward1 the bench holes under the center heading were also drilled4 ,the center heading explored the rock in advance of the full-width heading1 and gave a good idea as to the care needed in firing4 ,for the full-width-heading method1 ,fig4 #b1 ten drills were mounted on five columns set abreast across the face4 ,holes were drilled to form a cut near the center line between the tunnels4 ,the remainder of the holes were located so that they would draw into the cut4 ,the bench was frequently drilled from the same set-up of columns by turning the drills downward4 ,in sound rock this method proved to be the most rapid of any4 ,practically all trimming was left until immediately before the concreting4 ,it was then taken up as a separate operation1 but proved to be costly and tedious1 and a hindrance to the placing of the lining4 ,materials ,encountered4--,all the rock encountered was the familiar ,hudson schist1 but it varied widely in its mineral constituents and in its physical characteristics4 ,in many places where the rock surface was penetrated1 a fine sand was found that was probably quicksand4 ,the material above the rock in the open-cut sections was mostly sand4 ,illustration3 ,,fig4 #b4 ,,method ,,of ,,excavating ,,with ,,full-,,width ,,heading ,,cross-,,town ,,tunnels1 ,,manhattan ,,side ,,elevation ,,front ,,elevation ,,plan ,,showing ,,position ,,of ,,columns ,,for ,,drilling ,,face ,the concurrence of the watercourse1 shown on ,general ,viele's map of ,manhattan ,island 7,plate ,,ix,d71 with the points where difficulties in the construction of the tunnels were encountered has been noted in a previous paper4 ,in all cases where the course of this ancient stream was crossed 7except at its final intersection of #cc;d ,street71 the rock was found to be very soft and disintegrated1 a large quantity of water was encountered1 and heavy timbering was required4 ,the construction at these localities will be taken up later4 ,in addition1 disintegrated rock1 but of a less troublesome character1 was invariably met under the depressions in the rock surface developed by the borings from the streets and test holes from the tunnels4 ,many of these places required timbering1 and no timbering was elsewhere necessary except at the portals4 ,these coincident conditions were especially marked in #cb;d ,street1 which for a long distance closely adjoins the course of the former creek4 ,disposal of ,spoil4--,the materials excavated from the tunnels were dumped at the #ceth ,street pier on barges furnished by the ,railroad ,company under another contract1 and were towed to points near the ,bayonne peninsula where the spoil was used principally in the construction of the ,greenville ,freight ,yards and the line across the ,hackensack ,meadows to the tunnels4 ,details of this work will be given in a subsequent paper4 ,after ,december1 #aijg1 when the excavation was about #he completed1 the contractor furnished the barges and effected the complete disposal of the spoil4 ,difficulties of ,excavation4--,as stated in a previous paper1 the excavation of the ,twin ,tunnel in #cc;d ,street was continued westward to the west line of ,fifth ,avenue on the original grade4 ,at that point the contractor started three drifts in the three-track section4 ,the relation of the drifts to each other and to the cross-section are shown by ,fig4 #c4 ,the center heading was driven a little in advance of those on the sides4 ,at a distance of #fe ft4 west of ,fifth ,avenue the rock surface was broken through in the top of the heading1 and a very fine sand was encountered4 ,for some distance east of this point the rock was badly disintegrated1 and the heading required timbering4 ,through the soft material1 tight lagging was placed on the sides and roof of the heading1 and the face was protected by breast boards4 ,there was a moderate flow of water through the cracks1 and1 in spite of every effort1 some of the fine sand was constantly carried into the heading4 ,in one or two instances considerable ground was lost at the face4 ,on the evening of ,december #adth1 #aijf1 as a heavy coal wagon was passing along #cc;d ,street above the heading1 the rear wheels dropped through the asphalt pavement4 ,an examination disclosed a cavity under the pavement about #ad ft4 long1 #ab ft4 wide and #ad ft4 deep4 ,evidently1 the fine sand had gradually settled into the voids caused by the loss of material at the face1 and the settlement broke the brick sewer over the heading4 ,the sewer was temporarily repaired1 and the hole in the street was filled before morning4 ,a tight bulkhead was built across the heading1 and work was abandoned at that point4 ,the north drift was advanced to a point #ajh ft4 west of ,fifth ,avenue where sand was also encountered and a considerable run occurred4 ,after that time all work on the three-track section was discontinued4 ,the ,company then took up the consideration of changes in plan4 ,to determine the difficulties of driving a ,twin ,tunnel at a lower elevation1 an exploration drift1 #h ft4 high and #ab ft4 wide1 was driven on the center line of the street as a top heading on the proposed new grade4 ,test holes were drilled above this heading and to the sides4 ,the results indicated that there was sufficient rock cover of fair quality to enable the ,twin ,tunnel to be driven without great risk4 ,the new plan 7continuing the ,twin ,tunnel westward at a lower grade7 was adopted in ,march1 #aijg1 and work was immediately resumed at ,fifth ,avenue4 ,the relation between the cross-sections under the old and new plans at that point is shown by ,fig4 #c4 ,before the new section was excavated it was necessary to support the timber work in the old headings4 ,the plan adopted is also shown by ,fig4 #c4 ,the rock was excavated under the center heading1 as shown in cross-section1 for a length of about #c ft4 ,a girder composed of two #ah-;in4 ,i-beams was then put in position over each line and supported on the sides by posts4 ,the ends at the center lines between the tunnels were supported on short posts bearing on the rock bench4 ,the support of the timbering in the headings was then transferred to the girders by additional posts4 ,blocking was also inserted between the tops of the beams and the rock walls between the headings4 ,fig4 #b1 ,plate ,,lix1 gives a good idea of the timber work in the top headings above the ,i-beams4 ,when the roof had been made secure1 the removal of the bench was begun4 ,as the work advanced it was necessary to replace the short posts at the center of the tunnel by others of full height1 and there was considerable settlement in the ,i-beams during this operation4 ,when the bench had been removed to a point #fa ft4 west of ,fifth ,avenue1 settlement was detected in the street surface above4 ,bench excavation was suspended and a section of the permanent lining1 #ce ft4 long1 was placed4 ,the space between the lining and the beams and between the beams and the roof was filled with rubble masonry4 ,grout pipes were built into the masonry and later all voids were filled with grout4 ,fig4 #c1 ,plate ,,lix1 shows the first section of the concrete lining completed and part of the rubble in place2 and ,fig4 #d1 ,plate ,,lix1 shows details of the work above the tunnels4 ,a second section of bench was next removed and more lining was placed4 ,work was continued in this way until all the roof at the old three-track headings had been secured4 ,in this portion of the work the posts were embedded in the concrete4 ,between ,fifth and ,sixth ,avenues there were two more sections of bad rock where it was necessary to support the roof with steel beams4 ,at these latter points there were no complications with the excavation for the ,three-,track ,tunnel1 and the work was much simpler4 ,to avoid leaving the center posts in the permanent work1 two rows of temporary posts were placed1 as shown by ,fig4 #a1 ,plate ,,lx1 the center wall and skewback were built1 and the posts were removed1 as shown by ,fig4 #b1 ,plate ,,lx1 before placing the remainder of the lining4 ,in #cb;d ,street the normal progress of the excavation was frequently interrupted by encountering soft and unsound rock4 ,in the excavation between the ,east ,river and the ,intermediate ,shafts it was possible to overcome these conditions by temporarily narrowing the excavation on one side and supporting the roof on #af by #af-;in4 transverse timbers caught in niches in the rock at the sides1 leaving sufficient room for the steam shovel to work through4 ,in order to save time1 the height of the excavation was not increased before placing these timbers1 so that1 previous to the concreting1 they all required to be raised to clear the masonry lining and were then supported on posts on the center line between the tunnels4 ,this permitted the remainder of the excavation to be made1 and such additional timbering as was required was placed4 ,at most of these sections a brick arch and water-proofing were used1 on account of the presence of water4 ,in certain places the center line posts were buried in the core-wall1 and1 in order to permit the placing of the water-proofing1 were then cut off one by one flush with its top as the load was transferred to the completed masonry4 ,in other cases the load was transferred to posts clear of the masonry and the center line posts were entirely removed4 ,under such conditions the normal concrete methods1 to be described later1 could not be used1 and special forms were substituted4 ,illustration3 ,,fig4 #c4 ,,construction ,,of ,,twin ,,tunnels1 ,,through ,,excavation ,,started ,,for ,,three-,,track ,,tunnel ,,in #cc;,d ,,street ,,near #e,,th ,,avenue ,in this section of the work the most serious difficulties were encountered near ,fourth ,avenue a short distance east of the ,intermediate ,shaft1 and beneath the site of the old pond shown on ,general ,viele's map4 ,the rock cover was known from the boring to be very thin1 and the presence of the subway overhead caused some anxiety4 ,the excavation was at first taken out to practically full width and timbered1 but the rock became so treacherous that the heading was narrowed to a width sufficient for one tunnel only4 ,with this span the rock in the roof held without timbering4 ,as the masonry lining approached1 sufficient trimming was done to permit the placing of the core-wall and one arch4 ,above the completed core-wall and brick arch the voids were filled solid with rubble masonry to give an unyielding support to the roof4 ,the excavation of the remaining width of tunnel was then undertaken4 ,near the west side of ,fourth ,avenue1 the excavation broke out of rock at the top1 and fine sand and gravel with a large quantity of water were encountered4 ,the work of excavation was arduous1 and proceeded very slowly1 on account of the care with which it was executed4 ,only a small amount of sand entered the tunnel1 but the lining was placed as soon as the excavation was completed4 ,rubble masonry packing and grout ejected through pipes built into the arch were used to fill the voids above the roof4 ,as a further precaution against the settlement of the subway1 #b-;in4 pipes were washed down from the street above the point where soft ground was exposed in the roof of the tunnel1 and through them grout was forced into the ground at various depths4 ,careful levels show that no settlement of the subway has taken place4 ,west of the ,intermediate ,shaft the tunnel was excavated for full width until bad rock was encountered about #fj ft4 west of ,madison ,avenue4 7,see ,general ,viele's map1 ,plate ,,ix47 ,timbering was used for a short distance1 and then the heading and bench were narrowed to #ah ft41 and steam-shovel excavation was abandoned4 ,as the heading advanced the rock grew steadily softer1 the difficult conditions in this locality culminating when a slushy disintegrated feldspar was met1 requiring poling and breasting4 ,thereafter the rock improved markedly1 but near the east side of ,fifth ,avenue its thickness above the roof was found to be only #a-a_/b ft41 and the advance was stopped1 pending a decision as to a change of plan4 ,illustration3 ,,plate ,,lx1 ,,fig4 #a4--;,,double ,,row ,,of ,,posts ,,under ,i-,,beams1 ,,supporting ,,roof ,,in ,,bad ,,rock ,,section4 ,illustration3 ,,plate ,,lx1 ,,fig4 #b4--;,,center ,,wall ,,and ,,skewback ,,under ,i-,,beams1 ,,after ,,removal ,,of ,,double ,,row ,,of ,,posts4 ,illustration3 ,,plate ,,lx1 ,,fig4 #c4--,,timbering ,,in ,,full-,,width ,,heading ,,of ,,three-,,track ,,tunnel4 ,illustration3 ,,plate ,,lx1 ,,fig4 #d4--,,underpinning ,,walls ,,in ,,open-,,cut ,,section4 ,after some delay1 an exploration drift1 similar to the one already described1 was driven through to ,sixth ,avenue1 and a change in plan was made1 substantially the same as for the #cc;d ,street tunnels4 ,enlargement to full size was at once started1 but1 for #djj ft4 the rock was very soft and poor1 and required extremely careful handling4 ,the exploration drift was widened out to the full ,twin-,tunnel width1 and ,i-beams were placed and supported1 in much the same manner as in #cc;d ,street4 ,the rock was so soft that it was frequently necessary to drive poling boards ahead as the face was mined out with picks and shovels4 ,the load was very heavy1 and the work the most difficult encountered in the tunnels4 ,after this stage of the enlargement was reached1 the excavation of the bench and the placing of the lining proceeded alternately1 with the ,i-beams temporarily supported on long posts while the concrete core-wall was being built4 ,considerable settlement took place while shifting the posts1 and eventually showed on the street surface and in the adjacent sidewalk vaults1 but no damage was done to the structural portions of the buildings4 ,while the above work had been going on westward from ,fifth ,avenue1 the excavation of the ,twin ,tunnel eastward from the end of the open-cut section at ,sixth ,avenue had been proceeding rapidly1 and1 toward the end of the difficult ,fifth ,avenue work1 it was being attacked from both directions4 ,,progress ,,of ,,excavation4 ,owing to the numerous sections of poor rock1 interspersed throughout the work with stretches of sound rock1 the progress of the excavation was very irregular1 especially in #cb;d ,street4 ,the rate of excavation in good ground is shown in ,table #a4 ,in the sections of bad ground1 the operations of excavation1 timbering1 and lining were often carried on alternately1 and it is impracticable to include them in the table4 ,,table #a4--,,progress ,,and ,,methods ,,of ,,excavation ,,in ,,good ,,ground4 ,,thirty-,,third ,,street4 #a #b #c ---------------------------------------- ----------------- ,type of excavation4 ,tunnels4 ,worked from3 ---------------------------------------- ----------------- ,full-sized single tunnel ,b #ast ,ave4 shaft4 ,full-sized single tunnel ,a #ast ,ave4 shaft4 ,full-sized twin tunnel ,a and ,b #ast ,ave4 shaft4 ,full-sized twin tunnel ,a and ,b ,intermediate shaft4 7,west of shaft47 ,full-sized twin tunnel ,a and ,b ,intermediate shaft4 7,east of shaft47 ,full-sized twin tunnel ,a and ,b ,intermediate shaft4 7,east of shaft47 ,exploration drift ,a and ,b ,intermediate shaft4 7,west of shaft47 ,twin tunnel4 ,enlargement ,a and ,b ,west shaft4 of exploration drift 7,east of shaft47 #d #e #f #g ---------------------------------------- -------------------------- ,length ,average ,,dates4 ,time tunnel advance ----------------------------------elapse d1 excavated1 per day1 in in in ,from ,to days4 linear feet4linear feet4 ---------------------------------------- -------------------------- ,feb4 #bh1 #aijf4 ,may #ab1 #aijf4 #gd #cdf #d4g ,feb4 #bh1 #aijf4 ,apr4 #cj1 #aijf4 #fb #bee #d4a ,aug4 #bc1 #aijf4 ,jan4 #e1 #aijg4 #acf #ghi #e4h ,apr4 #d1 #aijf4 ,oct4 #ca1 #aijf4 #baj #gcj #c4e ,apr4 #d1 #aijf4 ,oct4 #ca1 #aijf4 #baj #ghc #c4g ,nov4 #a1 #aijf4 ,dec4 #bf1 #aijf4 #ef #caa #e4e ,mar4 #a1 #aijg4 ,july #bc1 #aijg4 #ade #idg #f4e ,sept4 #f1 #aijg4 ,dec4 #d1 #aijg4 #hi #fjc #f4h #h ---------------------------------------- ------------- ,methods and conditions4 ---------------------------------------- ------------- ,top heading and bench4 ,muck loaded by hand4 ,top full-width heading and bench4 ,muck loaded by steam shovel4 ,working exclusively on this heading4 ,top center heading and bench4 ,muck loaded by steam shovel4 ,working alternately in headings east and west of the shaft4 ,top center heading and bench4 ,muck loaded by steam shovel4 ,working alternately in headings east and west of the shaft4 ,top full-width heading and bench4 ,muck loaded by steam shovel working exclusively on this heading4 ,exploration drift about #i ft4 by #ab ft4 ,mucking by hand4 ,fourteen timber bents were placed in ,march1 and seven in ,april1 #aijg4 ,drift excavated to full width and bench4 ,muck loaded by steam shovel4 ,,thirty-,,second ,,street4 #a #b #c ---------------------------------------- ----------------- ,type of excavation4 ,tunnels4 ,worked from3 ---------------------------------------- ----------------- ,full-sized single tunnel ,c #ast ,ave4 shaft4 ,full-sized single tunnel ,d #ast ,ave4 shaft4 ,full-sized twin tunnel ,c and ,d #ast ,ave4 shaft4 ,narrowed twin tunnel ,c ,intermediate shaft4 7,east of shaft47 ,narrowed twin tunnel ,c ,intermediate shaft4 7,east of shaft47 ,full-sized twin tunnel ,c and ,d ,intermediate shaft4 7,west of shaft47 ,exploration drift ,c and ,d ,intermediate shaft4 7,west of shaft47 ,twin tunnel4 ,enlargement ,c and ,d ,eastward from of exploration drift open cut4 ,twin tunnel4 ,enlargement ,c and ,d ,eastward from of exploration drift open cut4 #d #e #f #g ---------------------------------------- -------------------------- ,length ,average ,,dates4 ,time tunnel advance ----------------------------------elapse d1 excavated1 per day1 in in in ,from ,to days4 linear feet4linear feet4 ---------------------------------------- -------------------------- ,jan4 #be1 #aijf4;,apr4 #cj1 #aijf4 #ie #cfg #c4i ,jan4 #bg1 #aijf4;,apr4 #cj1 #aijf4 #ic #ced #c4h ,may4 #bb1 #aijf4;,july #bd1 #aijf4;,e #agc #haj #d4g ,aug4 #aa1 #aijf4,nov4 #bi1 #aijf4 ,mar4 #ai1 #aijf4,may #bh1 #aijf4 #gj #eh #j4h ,may #bi1 #aijf4;,july #c1 #aijf4;,e #bjh #a1bjf #e4h ,july #ah1 #aijf4;,july #ca1 #aijf4 ,aug4 #ab1 #aijf4,nov4 #bc1 #aijf4 ,jan4 #ae1 #aijg4;,feb4 #e1 #aijg4 ,feb4 #ag1 #aijg4,mar4 #ba1 #aijg4 ,dec4 #a1 #aije4,may4 #aj1 #aijf4 #afa #bbe #a4d ,feb4 #a1 #aijg4,sept4#ac1 #aijg4 #bbe #a1jcc #d4f ,feb4 #a1 #aijh4;,feb4 #ad1 #aijh4 #ad #fe #d4f ,feb4 #ae1 #aijh4;,apr4 #ad1 #aijh4 #ei #ebd #h4i ,footnote ,e3 ,time and distance omitted while working through timbered stretches4 #h ---------------------------------------- --------------- ,methods and conditions4 ---------------------------------------- --------------- ,top heading and bench4 ,muck loaded by hand4 ,double heading and bench4 ,muck loaded by steam shovel4 ,stretches aggregating #bjj ft4 narrowed to about #be ft4 and later enlarged are included4 ,excavation about #cj ft4 wide4 ,top full-width heading and bench4 ,muck loaded by hand4 ,steam shovel not installed4 ,excavation about #cj to #ce ft4 wide4 ,top full-width by hand and part by steam shovel4 ,double heading and bench4 ,part of the muck handled by hand and part by steam shovel4 ,exploration drift about #aj ft4 by #ac in4 ,muck loaded by hand4 #ad ft4 timbered4 ,at portal of twin tunnels4 ,drift excavated to full width and bench4 ,muck loaded by hand4 #ab ft4 timbered4 ,drift excavated to full width and bench4 ,muck loaded by steam shovel4 ,full-width tunnel timbered for #bf ft4 independently of the main excavation4 ,,three-,,track ,,tunnel ,,excavation4 ,when it became evident that the work through the ,fifth ,avenue section would be extremely slow1 shafts were sunk in each street between ,sixth and ,seventh ,avenues4 ,the shafts1 as shown on ,plate ,,xiv1 were located in the streets1 but in such a way as to block only half of the roadway4 ,at the same time it was decided to construct in open cut about #bjj ft4 of the ,three-,track ,tunnel at the west end of the contract in #cb;d ,street1 where the rock surface was below the top of the tunnel4 ,it was hoped that the remainder of the work could be built without opening the street1 but further investigation showed that this was impracticable1 and eventually all the ,three-,track ,tunnel in #cb;d ,street1 except #abj ft4 east of the shaft1 was built in open cut4 ,thirty-second ,street ,work in ,tunnel4--,following the sinking of the shaft1 a drift was driven across the street at the crown of the tunnel1 and a top heading on the south side was excavated in both directions4 ,frequent cross-drifts to the north side showed that the rock was nowhere very sound and that1 except for a short distance east of the shaft1 it was distinctly unfavorable for the wide ,three-,track excavation4 ,in this stretch the north ends of these cross-cuts were connected by a second heading1 and wall-plates and sets of three-segment arch timbering were set up to support the roof of the drifts4 ,the cross-cuttings were gradually widened and timbered until the entire excavation had been made down to the level of the wall-plates1 as shown in ,fig4 #c1 ,plate ,,lx4 ,the bench was then excavated in two lifts1 leaving the wall-plates supported on narrow longitudinal berms1 which were removed in short sections to permit the placing of posts under the wall-plates4 ,thirty-second ,street ,open-,cut ,work4--,before actual open-cut excavation was started1 all buildings facing it were underpinned to rock4 ,for this purpose1 a trench was dug along the face of the buildings and of the same depth as their cellars4 ,holes were cut in the front foundation walls through which long needle-beams 7,fig4 #d1 ,plate ,,lx7 were inserted and jacked up on blocking placed on the cellar floor and in the trench1 until the weight of the building had been taken off its foundations4 ,a close-sheeted trench was then sunk to rock under the front building walls1 and a light rubble masonry retaining wall was built in it to support the building permanently4 ,frequently1 the excavation for the underpinning wall1 which was taken out in sections from #cj to #dj ft4 long1 and in places was carried to a depth of #dj ft41 was very troublesome on account of the large quantity of water encountered and the fineness of the sand1 which exhibited a tendency to flow when saturated4 ,the ,elevated ,railroad columns in ,sixth ,avenue1 near the north and south lines of #cb;d ,street1 were underpinned in a manner similar to the building foundations1 while those on the center line of the street were supported by girders riveted to them close under the track level4 ,the girders in turn were supported on posts footed on the new underpinning of the adjacent columns4 ,on the completion of the tunnels1 concrete piers were built up from the roof of the tunnel to form a permanent foundation for the center-line columns4 ,the area to be excavated under ,sixth ,avenue was enclosed by a rubble masonry retaining wall constructed in a trench4 ,open-cut excavation was started by planking over the street on stringers resting on transverse #ab by #ab-;in4 caps4 ,the caps were gradually undermined and supported on temporary posts which were then replaced by short posts resting on #ab by #ab-;in4 sills about #g ft4 below the cap4 ,the operation was then repeated and the sill was supported on another set of short posts resting on a second sill4 ,when the excavation had been carried down in this manner to the level of the top of the tunnel1 diagonal #c by #aj-;in4 timbers were cut in between the posts and sills to form a species of double ,a-frame1 the legs of which rested in niches cut in the rock and on posts carried up the face of the underpinning wall1 and the whole was stiffened with vertical tie-rods4 ,this construction is shown by ,fig4 #c1 ,plate ,,lxii4 ,the brick sewer was replaced temporarily by one of riveted steel pipe4 ,this pipe and the water and gas pipes and electric conduits were suspended from the timbers as the pipes were uncovered4 ,excavation in rock was made by sinking a pit to sub-grade for the full width of the tunnel and advancing the face of the pit in several lifts1 the muck being blown over the slope and loaded into buckets at its foot4 ,the work was attacked at several places simultaneously1 and the spoil was hoisted by derricks located at convenient points along the side of the cut4 ,thirty-third ,street ,work in ,tunnel and ,open ,cut4--,the ,west #cc;d ,street ,shaft was similar to the one in #cb;d ,street1 and was sunk during ,february1 ,march1 and ,april1 #aijg1 through #aj ft4 of earth1 #ba ft4 of soft rock1 and #bi ft4 of fairly hard rock4 ,it was necessary to timber heavily the upper #cj ft4 of the shaft4 ,the timber later showed evidences of severe strain1 and had to be reinforced4 ,illustration3 ,plate ,,lxi4--,,excavation ,,and ,,timbering ,,in ,,heavy ,,ground ,,of ,,three-,,track ,,tunnel ,,of #cc;,d ,,st4 ,as soon as the shaft excavation was deep enough1 a drift was driven part way across the tunnels1 and top headings were started both east and west to explore the rock4 ,the heading to the west was divided into two drifts1 as shown on ,plate ,,lxi4 ,these two drifts were continued to the west end of the contract1 and were then enlarged to a full-sized heading and timbered1 as shown on ,plate ,,lxi and ,fig4 #c1 ,plate ,,lx4 ,the rock near the shaft contained many wet rusty seams1 and settlement was detected in the segmental tunnel timbering soon after the widening of the heading was completed4 ,short props were placed under the timbers1 and the street surface was opened with a view of stripping the earth down to the rock and thus lightening the load on the timbering4 ,street traffic was maintained on a timber structure with posts eventually carried down to the rock surface1 and the walls of the buildings on the north side of the street were underpinned to rock4 ,the settlement of the tunnel timbering was checked for a time1 and the bench was excavated as shown on ,plate ,,lxi4 ,in this work the cut in the center was first made1 and the short props were replaced by struts1 as shown2 after this the berms were removed and the side posts were placed4 ,while building the brick arches1 holes were left in the masonry around the struts4 ,after the masonry had hardened1 piers were built on the arches to support the segmental timbers4 ,the struts were then removed and the openings filled with masonry4 ,the voids above the arch were packed with rock and afterward thoroughly grouted4 ,the timbers near the shaft continued to settle1 and1 although they had been placed from #i to #ab in4 above the level of the top of the masonry1 by ,october #ast1 they encroached #i in4 within the line of masonry4 ,it was then decided to remove the rock for a distance of #dh ft4 west of the shaft1 and build this portion of the tunnel in open cut4 ,the posts supporting the deck forming the street surface were replaced by an ,a-frame structure similar to that developed for the #cb;d ,street open cut1 without interruption of the street traffic4 ,after making the open cut to the westward of the shaft1 there was a slip in the rock north of and adjoining the shaft4 ,fortunately1 the timbers did not give way entirely1 and no damage was done4 ,the open cut was extended eastward for a distance of #df ft41 making the total length of tunnel built in open cut on this street #id ft4 ,east of the shaft1 for a distance of about #abe ft41 the rock was broken and could not be excavated to full size without timbering the roof1 but between this section of poor rock and those already mentioned in connection with the work at ,fifth ,avenue1 there was a stretch of #fjj ft4 of good rock where all the spoil was handled with a steam shovel4 ,,twin-,,tunnel ,,lining4 ,the masonry lining for the tunnels was not started until the late fall of #aijf1 after excavation had been in progress for a year and a half4 ,at that time concreting was started in the single tunnels westward from the ,first ,avenue ,shafts1 and by spring was in full swing in the ,twin ,tunnels4 ,the plans contemplated the use of a complete concrete lining except where large quantities of water were encountered2 in which case the arches1 beginning at a point #ae above the springing line1 were to be built of vitrified paving brick4 ,by reference to ,plate ,,xii it will be seen that the water-proofing1 which in the concrete-roof tunnels extended the full height of the sides to the #ae line1 was carried in the brick-roof tunnels completely around the extrados of the arch4 ,the cross-sections also show the location of the electric conduits which were buried in the mass of the side and core-walls and which limited the height to which the concrete could be carried in one operation4 ,the same general scheme of operations was used wherever possible throughout the ,twin-,tunnel work1 but was subject to minor modifications as circumstances dictated4 ,concrete was first deposited in the bottom1 to the grade of the flow line of the drains2 after it had set1 collapsible box forms1 of #b-;in4 plank with #c-;in4 plank tops1 were laid on it to form the ditch and the shoulders for the flagstone covers4 ,the track1 which had previously been blocked up on the rock between the ditches1 was raised and supported on the ditch boxes above the finished floor level4 ,at the same time1 light forms were braced from the ditch boxes to the grade of the base of the low-tension and telephone-duct bank4 ,after depositing the concrete to this level1 the telephone ducts were laid4 ,the forms for the water-proofing or sand-wall up to the #ae line and for the main side-walls and core-walls were built in #cj-;ft4 panels and were supported on carriages1 which1 traveling on a broad-gauge track above the ditches1 moved along the tunnel1 section by section1 as the work advanced4 ,the panels were hung loosely from joists carrying a platform on the top chord of the carriage trusses1 and were adjusted transversely by bracing and wedging them out from the carriage4 ,the small forms for the refuge niches1 ladders1 etc41 were collapsible1 and were spiked to the main panel forms just previous to the deposition of the concrete4 ,the concrete was deposited from the platform on top of the carriage1 to which the cars were elevated in various ways4 ,plate ,,lxi shows the details of the carriages1 and is self-explanatory4 ,the concrete for the sand-walls and the core-wall1 to the level of the sidewalk1 was deposited at the same time2 two carriages in each tunnel1 placed opposite each other1 forming a #fj-;ft4 length1 were used at each setting4 ,the floor section of the #d-;in4 tile drains had been laid with the floor concrete1 and1 as the sand-wall concrete was deposited1 the drains were brought up simultaneously1 broken stone being deposited between the tile and the rock to form a blind drain and afford access to the open joints of the tile for the water entering the tunnel through seams in the rock4 ,the drains were spaced at intervals not exceeding #be ft41 depending on the wetness of the rock1 and were placed at similar intervals in the core-wall under the lowest projecting points of the rock on the center line between the tunnels4 ,a small ditch lined with loose #f-;in4 vitrified half pipe was provided in the top of the sand-wall to collect the water from the extrados of the arch and lead it to the top of the drains4 ,great difficulty was experienced in maintaining these drains clear1 and1 on completion of the work1 a large amount of labor was expended in removing obstructions from the floor sections1 the only portion then accessible4 ,after water-proofing the sand-walls and laying the low-tension ducts1 a second pair of carriages1 with panels on one side only1 for #fj ft4 of side-wall and skewback to the #ae line1 were set and braced against the core-wall4 ,these forms are shown in connection with the carriage on ,plate ,,lxi4 ,they were concreted to the base of the high-tension duct bank1 and1 after the concrete had hardened and the bank of ducts had been laid1 the concreting was completed in a second operation4 ,in places where the roof was supported temporarily by posts and heavy timbering1 such as at ,fifth ,avenue1 the form carriages could not be used1 and special methods were devised to suit the local conditions4 ,usually1 the panels were stripped from the carriages and moved from section to section by hand1 and1 when in position1 were braced to the timbering4 ,the arch centers were built up of two #e by #c by #c_/h-;in4 steel angles1 and1 when set1 were blocked up on the sidewalks opposite each other in the two tunnels4 ,a temporary platform was laid on the bottom chord angles of the ribs1 on which the concrete was dumped1 the same as on the form carriages4 ,the lagging used was #c by #c-;in4 dressed pine or spruce #af ft4 long1 and was placed as the concreting of the arch proceeded above the #ae line on the side-wall and above the sidewalk on the core-wall4 ,after the arch had reached such a height that the concrete could not be passed over the lagging directly from the main platform1 it was cast on a small platform on the upper horizontal bracing of the centers1 shown in ,fig4 #c1 ,plate ,,lix1 and was thence shoveled into the work4 ,in the upper part of the arch the face of the concrete was kept on a radial plane1 and1 when only #c ft4 remained to be placed1 it was keyed in from one end1 the key lagging being set in about #e-;ft4 lengths4 ,the arches were concreted usually in #fj-;ft4 lengths4 ,where brick arches were used1 the core-wall skewback was concreted behind special forms set up on the sidewalks1 or the arch ribs and lagging were used for forms1 and the brick arch was not started until after the concrete had set4 ,in laying the brick in the arch1 the five courses of the ring were carried up as high as the void between the extrados and the rock would permit and still leave a working space in which to place the water-proofing4 ,this was usually not more than #c ft41 except on the core-wall side4 ,the felt and pitch water-proofing was then laid for that height1 joined to the previous water-proofing on the side-walls1 and was followed by the brick armor course over the water-proofing and by the rock packing1 after which another lift of brick was laid and the operations were repeated4 ,the large void 7,fig4 #a1 ,plate ,,lxii7 above the core-wall gave convenient access for working on top of the adjacent sides of the roof1 and the keying of the arches and the water-proofing and rock packing above the core-wall were usually carried on from that point1 the work progressing from one end4 ,the concrete for all work above the floor was dumped on the platform of the carriages1 to which it was transported in the early part of the work in cars running on a high-level track laid on long ties1 resting on the finished sidewalks4 ,this arrangement1 although requiring a large amount of timber for the track1 permitted the muck to be carried out on the low-level track without interference4 ,later1 when the advance of the heading had ceased and the heavy mucking was over1 all concrete was transported on the floor level1 and the cars were lifted to the carriage platforms by elevators and were hauled by hoisting engines up a movable incline4 ,the latter method is shown by ,fig4 #c1 ,plate ,,lix4 ,water-,proofing4--,the water-proofing referred to above was in all cases felt and pitch laid with six thicknesses of felt and seven of pitch4 ,the sub-contractor for the work was the ,sicilian ,asphalt ,paving ,company4 ,all joints were lapped at least #a ft41 and1 where work was suspended for a time and a bevel lap could not be made1 the edges of the felt were left unpitched for #a ft4 and the newer work was interlaced with the old4 ,this method was not always successful1 however1 on account of the softening of the unpitched felt on long-continued exposure to the water4 ,the felt used was mainly ,tunaloid1 together with some ,hydrex4 ,it weighed about #ab lb4 per #ajj sq4 ft4 when saturated and coated on one side only1 and contained about #be of wool4 ,the coal-tar pitch used had a melting point of #ajj ,fahr4 ,after the completion of the tunnel1 the concrete arch showed some leakage and in places unsightly lime deposits4 ,it was determined to attempt to stop these leaks by the application of a water-proof cement coating on the intrados of the arch4 ,extended experimental application of two varieties of materials used for this purpose--,hydrolithic cement and the ,u4 ,s4 ,water-proofing ,company's compound--have been made with apparent success up to the present time1 and the results after the lapse of a considerable period are awaited with interest4 ,duct ,laying4--,the position of the electric conduits1 buried in the heart of the concrete walls1 interfered greatly with the economical and speedy placing of the lining1 and their laying proved to be one of the most troublesome features of the work4 ,the power conduits were single-way1 with the bank for high-tension cables separated in the side-walls from the low-tension bank1 as shown on ,plate ,,xii4 ,the conduits for telephone and telegraph service were four-way1 and were located in the core-wall4 ,all ducts had #c_/d-;in4 walls and a minimum clear opening of #c-c_/h in4 square1 with corners rounded4 ,they were laid with joints broken in all directions1 and in about #a_/d-;in4 beds of #a3b-a_/b mortar4 ,flat steel bond-irons1 #b by #a_/h in41 with split and bent ends1 were placed in the joints at intervals of #c ft4 and projected into the concrete #c in4 on each side1 tying together the concrete on opposite sides of the ducts4 ,the joints were wrapped with a #f-;in4 strip of #aj-oz4 duck saturated with neat-cement grout1 and1 in addition1 the power conduits were completely covered with a #a_/b-;in4 coat of mortar to prevent the intrusion of cement and sand from the fluid concrete4 ,the four-way conduits were plastered only over the wraps4 ,splicing chambers were provided at intervals of #djj ft4 ,illustration3 ,,plate ,,lxii1 ,,fig4 #a4--,,water-,,proofing ,,over ,,brick ,,arches4 ,illustration3 ,,plate ,,lxii1 ,,fig4 #b4--,,trestle ,,used ,,in ,,concreting ,,in ,,three-,,track ,,tunnel4 ,illustration3 ,,plate ,,lxii1 ,,fig4 #c4--,,method ,,of ,,street ,,support ,,over ,,open-,,cut ,,excavation4 ,illustration3 ,,plate ,,lxii1 ,,fig4 #d4--;,,junction ,,of ,,twin ,,and ,,three-,,track ,,tunnels4 ,,three-,,track ,,tunnel ,,lining4 ,in the ,three-,track ,tunnels1 a heavy brick arch was used for those portions constructed in tunnel1 while1 in the open-cut sections1 the roof was of concrete4 ,both were completely water-proofed on the roof and sides1 and in the tunnel sections the space above the brick roof was filled with rock packing4 ,on account of the unstable nature of the rock encountered throughout1 the voids in the packing were afterward filled with grout4 ,by reference to the cross-sections1 ,plate ,,xii1 it will be seen that the haunches of the arch were tied together by steel ,i-beams anchored in the concrete1 with the object of making the structure self-supporting in the event of the removal of the adjacent rock for deep cellar excavations4 ,this construction materially influenced the contractor's method of placing the masonry lining4 ,after depositing the floor concrete1 by the same method that was used in the ,twin ,tunnels1 a timber trestle 7,fig4 #b1 ,plate ,,lxii7 was erected to the height of the underside of the ,i-beam ties1 the posts being footed in holes1 about #c in4 deep1 left in the concrete floor to prevent slipping4 ,in the open-cut sections the sand-wall forms were of undressed plank tacked to the studding and braced from the trestle2 in the tunnel section they were spiked to the face of the posts supporting the timbering4 ,the side-wall forms were made up in panels about #c by #aj ft41 and were clamped to studs by ,u-shaped irons passing around the stud and bolted to the cleats on the back of the panels1 the studs being braced from the trestle4 ,the side-wall concrete was deposited in three sections4 ,the first was brought up just above the sidewalk and formed the bench for the high-tension ducts2 the second carried the wall up to the springing line4 ,before placing the third section the ,i-beam ties were set in position 7,fig4 #c1 ,plate ,,lxii7 on top of the trestle1 and the reinforcing rods in the haunch of the arch were hung from them4 ,the concrete was carried up to a skewback for the arch1 as shown in the brick-roof cross-section 7,plate ,,xii7 and embedded the ends of the ties4 ,the centers for the arches stood on the ,i-beam ties1 and the tops of the hangers1 for the permanent support of the ties near their center1 were inserted through the lagging4 ,the brick arch1 water-proofing1 and rock packing were laid up in lifts1 in the same manner as in the ,twin ,tunnel1 with grout pipes built in at intervals of about #h ft4 ,the concrete arch was placed in sections1 from #be to #ej ft4 in length1 with a rather wet mixture and a back form on the steep slope of the extrados4 ,the concrete for the sand-walls and lower part of side-walls was handled on tracks and platforms laid on cantilever beams at mid-height of the trestle1 as shown by ,fig4 #c1 ,plate ,,lxii4 ,for the walls above the springing line1 the tracks were laid on top of the ,i-beam ties1 and some of the arch concrete1 also1 was delivered from the mixer at that level and hauled up an incline to the level of the top of the arch4 ,by far the greater part1 however1 was turned out from mixers set on the completed arch1 and was transported on tracks hung in part from the street timbering4 ,completion4--,except in the heavily-timbered portions1 such as at ,fifth ,avenue1 where the load had to be transferred from posts to the completed masonry section by section1 the lining of the tunnels presented no special difficulty4 ,the large number of small forms to be set1 and the mutual interference of the concreting and duct-laying operations proved to be the most troublesome features of the work4 ,the restoration of the streets1 public utilities1 etc41 at the open-cut sections was a slow and tedious operation1 but the tunnels themselves were completed in ,march1 #aiji1 #c years and #aj months after the inception of the work4 ,the finished tunnels are shown by the photograph1 ,fig4 #d1 ,plate ,,lxii1 taken at the junction of the twin and three-track types4 ,,footnotes3 ,footnote ,a3 ,presented at the meeting of ,december #ast1 #aiji4 ,footnote ,b3 ,of the paper by ,mr4 ,noble4 ,footnote ,c3 ,of the paper by ,mr4 ,noble4 ,footnote ,d3 ,of the paper by ,mr4 ,noble4