,,american ,,society ,,of ,,civil ,,engineers ,,instituted #aheb ,,transactions ,paper ,no4 #aaei ,,the ,,new ,,york ,,tunnel ,,extension ,,of ,,the ,,pennsylvania ,,railroad4 ,,the ,,east ,,river ,,tunnels4,a ,,by ,,james ,h4 ,,brace1 ,,francis ,,mason1 ,,and ,s4 ,h4 ,,woodard1 ,,members1 ,,am4 ,,soc4 ,c4 ,e4 ,this paper will be limited to a consideration of the construction of the tunnels1 the broader questions of design1 etc41 having already been considered in papers by ,brig4-,gen4 ,charles ,w4 ,raymond1 ,m4 ,am4 ,soc4 ,c4 ,e41 and ,alfred ,noble1 ,past-,president1 ,am4 ,soc4 ,c4 ,e4 ,the location of the section of the work to be considered here is shown on ,plate ,,xiii of ,mr4 ,noble's paper4 ,there are two permanent shafts on each side of the ,east ,river and four single cast-iron tube tunnels1 each about #f1jjj ft4 long1 and consisting of #c1ijj ft4 between shafts under the river1 and #b1jjj ft4 in ,long ,island ,city1 mostly under the depot and passenger yard of the ,long ,island ,railroad4 ,this tube-tunnel work was naturally a single job4 ,the contract for its construction was let to ,s4 ,pearson and ,son1 ,incorporated1 ground being broken on ,may #agth1 #aijd4 ,five years later1 to a day1 the work was finished and received its final inspection for acceptance by the ,railroad ,company4 ,the contract was of the profit-sharing type1 and required an audit1 by the ,railroad ,company1 of the contractor's books1 and a careful system of cost-keeping by the ,company's engineers1 so that it is possible to include in the following some of the unit costs of the work4 ,these are given in two parts3 ,the first is called the unit labor cost1 and is the cost of the labor in the tunnel directly chargeable to the thing considered4 ,it does not include the labor of operating the plant1 nor watchmen1 yardmen1 pipemen1 and electricians4 ,the second is called top charges1 a common term1 but meaning different things to different contractors and engineers4 ,here1 it is made to include the cost of the contractor's staff and roving laborers1 such as pipemen1 electricians1 and yardmen1 the cost of the plant and its operation1 and all miscellaneous expenses1 but does not include any contractor's profit1 nor cost of materials entering permanent work4 ,the contractor's plant is to be described in a paper by ,henry ,japp1,b ,m4 ,am4 ,soc4 ,c4 ,e41 and will not be dealt with here4 ,the contractors carried on their work from three different sites4 ,from permanent shafts1 located near the river in ,manhattan1 four shields were driven eastward to about the middle of the river2 and1 from two similar shafts at the river front in ,long ,island ,city1 four shields were driven westward to meet those from ,manhattan4 ,from a temporary shaft1 near ,east ,avenue1 ,long ,island ,city1 the land section of about #b1jjj ft4 was driven to the river shafts4 ,footnote ,a3 ,presented at the meeting of ,december #aeth1 #aiji4 ,footnote ,b3 ,transactions1 ,am4 ,soc4 ,c4 ,e41 ,vol4 ,,lxix4 p4 #a4 ,,tunnels ,,from ,,east ,,avenue ,,to ,,the ,,river ,,shafts4 ,the sinking of the temporary shaft at ,east ,avenue was a fairly simple matter4 ,rough #f by #ab-;in4 sheet-piling1 forming a rectangle1 #abg by #cd ft41 braced across by heavy timbering1 was driven about #bh ft4 to rock as the excavation progressed4 ,below this1 the shaft was sunk into rock1 about #bg ft41 without timbering4 ,as soon as the shaft was down1 on ,september #cjth1 #aijd1 bottom headings were started westward in ,tunnels ,a1 ,b1 and ,d4 ,when these had been driven about half the distance to the river shafts1 soft ground was encountered4 7,see ,station #ei1 ,plate ,,xiii47 ,as the ground carried considerable water1 it was decided to use compressed air4 ,bulkheads were built in the heading1 and1 with an air pressure of about #ae lb4 per sq4 in41 the heading was driven through the soft ground and into rock by ordinary mining methods4 ,the use of compressed air was then discontinued4 ,west of this soft ground1 a top heading1 followed by a bench1 was driven to the soft ground at about ,station #ff4 ,tunnel ,c1 being higher1 was more in soft ground1 and at first it was the intention to delay its excavation until it had been well drained by the bottom headings in the tunnels on each side4 ,a little later it was decided to use a shield without compressed air4 ,this shield had been used in excavating the stations of the ,great ,northern and ,city ,tunnel in ,london4 ,it was rebuilt1 its diameter being changed from #bd ft4 #h-a_/b in4 to #bc ft4 #e-a_/d in4 ,it proved too weak1 and after it had flattened about #d in4 and had been jacked up three times1 the scheme was abandoned1 the shield was removed1 and work was continued by the methods which were being used in the other tunnels4 ,the shield was rather light1 but probably it would have been strong enough had it been used with compressed air1 or had the material passed through been all earth4 ,here1 there was a narrow concrete cradle in the bottom1 with rock up to about the middle of the tunnel1 which was excavated to clear the shield1 and gave no support on its sides4 ,the shield was a cylinder crushed between forces applied along the top and bottom4 ,with the exception of this trial of a shield in ,tunnel ,c1 and a novel method in ,tunnel ,b1 where compressed air1 but no shield1 was used1 the description of the work in one tunnel will do for all4 ,from the bottom headings break-ups were started at several places in each tunnel where there was ample cover of rock above4 ,where the roof was in soft ground1 top headings were driven from the points of break-up and timbered4 ,as soon as the full-sized excavation was completed1 the iron lining was built1 usually in short lengths4 ,it will be noticed on ,plate ,,xiii that there is a depression in the rock between ,station #fe and the river shafts1 leaving all the tunnels in soft ground4 ,as this was directly under the ,long ,island ,railroad passenger station1 it was thought best to use a shield and compressed air4 ,this was done in ,tunnels ,a1 ,c1 and ,d1 one shield being used successively for all three4 ,it was first erected in ,tunnel ,d at ,station #fd #dg4 ,from there it was driven westward to the river shaft4 ,it was then taken apart and re-erected in ,tunnel ,c at ,station #fc #fc and driven westward to the shaft4 ,it was then found that there would not be time for one shield to do all four lines4 ,the experience in ,tunnels ,c and ,d had proven the ground to be much better than had been expected4 ,there was considerable clay in the sand1 and1 with the water blown out by compressed air1 it was very stable4 ,a special timbering method was devised1 and ,tunnel ,b was driven from ,station #ff #aj to the shaft with compressed air1 but without a shield4 ,in the meantime the shield was re-erected in ,tunnel ,a and was shoved through the soft ground from ,station #fe #dh nearly to the river shaft1 where it was dismantled4 ,there was nothing unusual about the shield work2 it was about the same as that under the river1 which is fully described elsewhere4 ,in spite of great care in excavating in front of the shield1 and prompt grouting behind it1 there was a small settlement of the building above1 amounting to about #a-a_/b in4 in the walls and about #e in4 in the ground floors which were of concrete laid like a sidewalk directly upon the ground4 ,whether this settlement was due to ground lost in the shield work or to a compacting of the ground on account of its being dried out by compressed air1 it is impossible to say4 ,the interesting features of this work from ,east ,avenue to the river shafts are the mining methods and the building of the iron tube without a shield4 ,,excavation ,,in ,,all ,,rock4 ,where the tunnel was all in good rock two distinct methods were used4 ,the first was the bottom-heading-and-break-up1 and the second1 the top-heading-and-bench method4 ,the first is illustrated by ,figs4 #a and #b1 ,plate ,,lxiii4 ,the bottom heading1 #ac ft4 wide and #i ft4 high1 having first been driven1 a break-up was started by blasting down the rock1 forming a chamber the full height of the tunnel4 ,the timber platform1 shown in the drawing1 was erected in the bottom heading1 and extended through the break-up chamber4 ,the plan was then to drill the entire face above the bottom heading and blast it down upon the timber staging1 thus maintaining a passage below for the traffic from the heading and break-ups farther down the line4 ,starting with the condition indicated by ,plate ,,xiii1 the face was drilled1 the columns were then taken down and the muck pile was shoveled through holes in the staging into muck cars below4 ,the face was then blasted down upon the staging1 the drill columns were set up on the muck pile1 and the operation was repeated4 ,this method has the advantage that the bottom heading can be pushed through rapidly1 and from it the tunnel may be attacked at a number of points at one time4 ,it was found to be more expensive than the top-heading-and-bench method1 and as soon as the depression in the rock at about ,station #ei was passed1 a top heading about #g ft4 high1 and roughly the segment of a #bc-;ft4 circle1 was driven to the next soft ground in each of the four tunnels4 ,the remainder of the section was taken out in two benches1 the first1 about #d ft4 high1 was kept about #ae ft4 ahead of the lower bench1 which was about the remaining #aa ft4 high4 ,,excavation ,,in ,,earth ,,and ,,rock4 ,about #b1ejj ft4 of tunnel1 the roof of which was in soft ground1 was excavated in normal air by the mining-and-timbering method4 ,in the greater part of this the rock surface was well above the middle of the tunnel4 ,the method of timbering and mining1 while well enough known1 has not been generally used in the ,united ,states4 ,illustration3 ,,plate ,,lxiii ,starting from the break-up in all rock1 as described above1 and illustrated on ,plate ,,xiii1 when soft ground was approached1 a top heading was driven from the rock into and through the earth4 ,this heading was about #g ft4 high and about #f ft4 wide4 ,this was done by the usual post1 cap1 and poling-board method4 ,the ground was a running sand with little or no clay1 and1 at first1 considerable water1 in places4 ,all headings required side polings4 ,the roof poling boards were about #b-a_/b or #c ft4 above the outside limit of the tunnel lining1 as illustrated by ,figs4 #c1 #d1 and #e1 ,plate ,,lxiii4 ,the next step was to place two crown-bars1 ,,aa1 usually about #bj ft4 long1 under the caps4 ,posts were then placed under the bars1 and poling boards at right angles to the axis of the tunnel were then driven out over the bars4 ,as these polings were being driven1 the side polings of the original heading were removed1 and the earth was mined out to the end of these new transverse polings4 ,breast boards were set on end under the ends of the transverse polings when they had been driven out to their limit4 ,side bars1 ,,bb1 were then placed as far out as possible and supported on raking posts4 ,these posts were carried down to rock1 if it was near1 if not1 a sill was placed4 ,a new set of transverse polings was driven over these side bars and the process was repeated until the sides had been carried down to rock or down to the elevation of the sills supporting the posts1 which were usually about #d ft4 above the axis of the tunnel4 ,the plan then was to excavate the remainder of the section and build the iron lining in short lengths1 gradually transferring the weight of the roof bars of the iron lining as the posts were taken out4 ,this meant that not more than four rings1 and often only one ring1 could be built before excavation and a short length of cradle became necessary4 ,before the posts under the roof bars could be built and the weight transferred to the iron lining1 a grout dam was placed at the leading end of the iron lining1 and grout was brought up to at least #de from the top4 ,such workings were in progress at as many as eight places in one tunnel at the same time4 ,where there was only the ordinary ground-water to contend with1 the driving of the top heading drained the ground very thoroughly1 and the enlarging was done easily and without a serious loss of ground4 ,under these conditions the surface settlement was from #f in4 to #b ft4 ,under ,borden ,avenue1 there was more water1 which probably came from a leaky sewer2 it was not enough to form a stream1 but just kept the ground thoroughly saturated4 ,there was a continued though hardly perceptible flow of earth through every crevice in the timbering during the six or eight weeks between the driving of the top heading and the placing of the iron lining2 and here there was a settlement of from #d to #h ft4 at the surface4 ,,tunneling ,,in ,,compressed ,,air ,,without ,a ,,shield4 ,when it became evident that there would not be time for one shield to do the soft ground portions of all four tunnels under the ,long ,island ,railroad station1 a plan was adopted and used in ,tunnel ,b which1 while not as rapid1 turned out to be as cheap as the work done by the shields4 ,figs4 #f and #g1 ,plate ,,lxiii1 and ,fig4 #a1 ,plate ,,lxiv1 illustrate this work fairly well4 ,the operation of this scheme was about as follows3 ,having the iron built up to the face of the full-sized excavation1 a hole or top heading1 about #c ft4 wide and #d or #e ft4 high1 was excavated to about #aj ft4 in advance4 ,this was done in a few hours without timbering of any kind2 but1 as soon as the hole or heading was #aj ft4 out1 #f by #ab-;in4 laggings or polings were put up in the roof1 with the rear ends resting on the iron lining and the leading ends resting on vertical breast boards4 ,the heading was then widened out rapidly and the lagging was placed1 down to about #de from the crown4 ,the forward ends of the laggings were then supported by a timber rib and sill4 ,protected by this roof1 the full section was excavated1 and three rings of the iron lining were built and grouted1 and then the whole process was repeated4 ,illustration3 ,,plate ,,lxiv1 ,,fig4 #a4--,,tunneling ,,in ,,compressed ,,air ,,without ,,shield4 ,illustration3 ,,plate ,,lxiv1 ,,fig4 #b4--,t-,,head ,,air-,,lock4 ,illustration3 ,,plate ,,lxiv1 ,,fig4 #c4--;,,cutting ,,edge ,,of ,,caisson ,,assembled4 ,illustration3 ,,plate ,,lxiv1 ,,fig4 #d4--;,,caisson ,,supported ,,on ,,jacks ,,and ,,blocks4 ,,concrete ,,cradles1 ,,hand-,,packed ,,stone ,,and ,,grouting4 ,had the ,east ,avenue ,tunnel been built by shields1 as was contemplated at the time of its design1 the space between the limits of excavation and the iron lining would have been somewhat less than by the method actually used1 especially in the earth portions4 ,this space would have been filled with grout ejected through the iron lining4 ,the change in the method of doing the work permitted the use of cheaper material1 in place of part of the grout1 and1 at the same time1 facilitated the work4 ,the tube of cast-iron rings is adapted to be built in the tail of the shield4 ,where no shield was used1 after the excavation was completed and all loose rock was removed1 timbers were fixed across the tunnel from which semicircular ribs were hung1 below which lagging was placed4 ,the space between this and the rough rock surface was filled with concrete4 ,this formed a cradle in which the iron tube could be erected1 and1 at the same time1 occupied space which would have been filled by grout1 at greater cost1 had a shield been used4 ,as soon as each ring of iron was erected1 the space between it and the roof of the excavation was filled with hand-packed stone4 ,at about every sixth ring a wall of stone laid in mortar was built between the lining and the rock to serve as a dam to retain grout4 ,the interstices between the hand-packed stones were then filled with #a to #a grout of cement and sand1 ejected through the iron lining4 ,the concrete cradles averaged #a4je cu4 yd4 per ft4 of tunnel1 and cost1 exclusive of materials1 #f4gj per cu4 yd41 of which #b4be was for labor and #d4de was for top charges4 ,the hand-packed stone averaged #a-a_/b cu4 yd4 per ft4 of tunnel1 and cost #b4db per cu4 yd41 of which #j4ih was for labor and #a4dd was for top charges4 ,,erection ,,of ,,iron ,,lining4 ,the contractors planned to erect the iron lining with erectors of the same pattern as that used on the shield under the river1 mounted on a traveling stage4 ,these will be described in detail in ,mr4 ,japp's paper4 ,two of these stages and erectors worked in each tunnel at different points4 ,the tunnel was attacked from so many points that these erectors could not be moved from working to working4 ,the result was that about #eh of the lining was built by hand4 ,at first thought1 this seems to be a crude and extravagant method1 as the plates weighed about #a ton each and about #bj1jjj were erected by hand4 ,as it turned out1 the cost was not greater than for those erected by machinery1 taking into account the cost of erectors and power4 ,this1 however1 was largely because the hand erection reduced the amount of work to be done by the machines so much that the machines had an undue plant charge4 ,the hand erection was very simple4 ,a portable hand-winch1 with a #c_/h-;in4 wire rope1 was set in any convenient place4 ,the wire rope was carried to a snatch-block fastened to the top of the iron previously built2 or1 where the roof was in soft ground1 the timbering furnished points of attachment4 ,the end of the wire rope was then hooked to a bolt hole in a new plate1 two men at the winch lifted the plate1 and three or four others swung it into approximate place1 and1 with the aid of bars and drift-pins1 coaxed it into position and bolted it4 ,where there was no timbering above the iron1 sometimes the key and adjoining plates were set on blocking on a timber staging and then jacked up to place4 ,,long ,,island ,,shafts4 ,the river shafts were designed to serve both as working shafts and as permanent openings to the tunnels1 and were larger and more substantial than would have been required for construction purposes4 ,plate ,x of ,mr4 ,noble's paper shows their design4 ,they consist of two steel caissons1 each #dj by #gd ft4 in plan1 with walls #e ft4 thick filled with concrete4 ,a wall #f ft4 thick separated each shaft into two wells #bi by #cj ft41 each directly over a tunnel4 ,circular openings for the tunnel1 #be ft4 in diameter1 were provided in the sides of the caissons4 ,during the sinking these were closed by bulkheads of steel plates backed by horizontal steel girders4 ,the shafts were sunk as pneumatic caissons to a depth of #gh ft4 below mean high water4 ,there have been a few caissons which were larger and were sunk deeper than these1 but most large caissons have been for foundations1 such as bridge piers1 and have been stopped at or a little below the surface of the rock4 ,the unusual feature of the caissons for the ,long ,island shaft is that they were sunk #ed ft4 through rock4 ,it had been hoped that the rock would prove sound enough to permit stopping the caissons at or a little below the surface and continuing the excavation without sinking them further2 for this reason only the steel for the lower #dj ft4 of the caissons was ordered at first4 ,the roof of the working chamber was placed #g ft4 above the cutting edge4 ,it was a steel floor1 designed by the contractors1 and consisted of five steel girders1 #f ft4 deep1 #bi ft4 long1 and spaced at #e-;ft4 centers4 ,between were plates curved upward to a radius of #d ft4 ,each working chamber had two shafts1 #c ft4 by #e ft4 in cross-section1 with a diaphragm dividing it into two passages1 the smaller for men and the larger for muck buckets4 ,on top of these shafts were ,moran locks4 ,mounted on top of the caisson was a #e-ton ,wilson crane1 which would reach each shaft and also the muck cars standing on tracks on the ground level beside the caissons4 ,circular steel buckets1 #b ft4 #f in4 in diameter and #c ft4 high1 were used for handling all muck4 ,these were taken from the bottom of the working chamber1 dumped in cars1 and returned to the bottom without unhooking4 ,work was carried on by three #h-;hour shifts per day4 ,the earth excavation was done at the rate of about #fg cu4 yd4 per day from one caisson4 ,the rock excavation1 amounting to about #f1bjj cu4 yd4 in each caisson1 was done at the rate of about #dd4e cu4 yd4 per day4 ,the average rate of lowering1 when the cutting edge of the south caisson was passing through earth1 was #j4g ft4 per day4 ,in rock1 the rate was #j4dh ft4 per day in the south caisson1 and #j4ci ft4 per day in the north caisson4 ,at the beginning all lowering was done with sixteen hydraulic jacks4 ,temporary brackets were fastened to the outside of the caisson4 ,a #ajj-ton hydraulic jack was placed under each alternate bracket and under each of the others there was blocking4 ,the jacks were connected to a high-pressure pump in the power-house4 ,as the jacks lifted the caisson1 the blocking was set for a lower position1 to which the caisson settled as the jacks were exhausted4 ,after the caisson had penetrated the earth about #aj ft41 the outside brackets were removed and the lowering was regulated by blocking placed under brackets in the working chamber4 ,the caisson usually rested on three sets of blockings on each side and two on each end4 ,the blocking was about #d ft4 inside the cutting edge4 ,in the rock1 as the cutting edge was cleared for a lowering of about #b ft41 #f by #h-;in4 oak posts were placed under the cutting-edge angle4 ,when a sufficient number of posts had been placed1 the blocking on which the caisson had rested was knocked or blasted out1 and the rock underneath was excavated4 ,the blocking was then re-set at a lower elevation4 ,the posts under the cutting edge were then chopped part way through and the air pressure was lowered about #aj lb41 which increased the net weight to more than #d1jjj1jjj lb4 ,the posts then gradually crushed and the caissons settled to the new blocking4 ,the tilt or level of the caisson was controlled by chopping the posts more on the side which was desired to move first4 ,the caisson nearly always carried a very large net weight1 usually about #hgj tons4 ,the concrete in the walls1 which was added as the caisson was being sunk1 was kept at about the elevation of the ground4 ,there was generally a depth of from #e to #bj ft4 of water ballast on top of the roof of the working chamber4 ,the air pressure in the working chamber was usually much less than the hydrostatic head outside the caisson4 ,for example1 the average air pressure in the south caisson during ,january1 #aijf1 was #af-a_/b lb41 while the average head was #fb4e ft41 equivalent to #bg lb4 per sq4 in4 ,under these conditions1 there was a continued but small leakage into the caisson of from #ae1jjj to #bj1jjj gal4 per day4 ,in the rock the excavation was always carried from #b to #e in4 outside the cutting edge4 ,as soon as the cutting edge was cleared1 bags of clay were placed under it in a well-tiered1 solid pile1 so that when the caisson was lowered the bags were cut through and most of the clay1 bags and all1 was squeezed back of the cutting edge between the rock and the caisson4 ,table #a shows the relation of the final position of the caissons to that designed4 ,the cost of rock excavation in the caisson was #d4dh per cu4 yd4 for labor and #aj4ed for top charges4 ,the bottom of the shaft is an inverted concrete arch1 #d ft4 thick1 water-proofed with #f-ply felt and pitch4 ,as soon as the caisson was down to its final position and the excavation was completed1 concrete was deposited on the uneven rock surfaces1 brought up to the line of the water-proofing1 and given a smooth #a-;in4 mortar coat4 ,the felt was stuck together in #c-ply mats on the surface with hot coal-tar pitch4 ,these were rolled and sent down into the working chamber1 where they were put down with cold pitch liquid at #fj ,fahr4 ,each sheet of felt overlapped the one below #f in4 ,the water-proofing was covered by a #a-;in4 mortar plaster coat1 after which the concrete of the #d-;ft4 inverted arch was placed4 ,while the water-proofing and concreting were being done1 the air pressure was kept at from #cj to #cc lb4 per sq4 in41 the full hydrostatic head at the cutting edge4 ,after standing for ten days1 the air pressure was taken off1 and the removal of the roof of the working chamber was begun4 ,the water-proofing was done by the ,union ,construction and ,waterproofing ,company4 ,,table #a4--,,relation ,,of ,,the ,,final ,,position ,,of ,,the ,,caissons ,,to ,,that ,,designed4 ,,location4 ,,long ,,island ,,city4 ---------------------------------------- ------------------------ ,shaft4 ,north4 ,south4 ---------------------------------------- ------------------------ ,corner4 ,high4 ,east4 ,north4 ,high4 ,east4 ,north4 ---------------------------------------- ------------------------ ,northeast#j4ba ft4#j4jh ft4#j4je ft4#j4cb ft4#j4ae ft4#j4bh ft4 ,northwest#j4bb #j4jh #j4jb #j4jj #j4ae #j4ab ,southwest#j4bg #j4ad #j4jb #j4ah #j4de #j4ab ,southeast#j4bc #j4ad #j4je #j4ci #j4de #j4bh ,,location4 ,,manhattan4 ---------------------------------------- ------------------------------------- ,shaft4 ,north4 ,south4 ---------------------------------------- ------------------------------------- ,corner4 ,high4 ,east4 ,south4 ,high4 ,east or ,west4,north or ,south4 ---------------------------------------- ------------------------------------- ,northeast#j4bc ft4#j4gd ft4#j4ch ft4#j4jj ft4#j4jf ft4 east4#j4jd ft4 south4 ,northwest#j4jj #j4gd #j4bb #j4jh #j4jf #j4ac north4 ,southwest#j4aa #j4ca #j4bb #j4ba #j4de west4#j4ac ,southeast#j4df #j4ca #j4ch #j4jd #j4de #j4jd south4 ,the cost of labor in compressed air chargeable to concreting was #c4dj per cu4 yd4 ,after the roof of each working chamber had been removed1 the shield was erected on a timber cradle in the bottom of the shaft1 in position to be shoved out of the opening in the west side of the caisson4 ,temporary rings of iron lining were erected across the shaft in order to furnish something for the shield jacks to shove against4 ,the roof of the working chamber was then re-erected about #ce ft4 above its original position and about #h ft4 above the tunnel openings4 ,this time1 instead of the two small shafts which were in use during the sinking of the caisson1 a large steel shaft with a ,t-head lock was built4 ,this is illustrated in ,fig4 #b1 ,plate ,,lxiv4 ,the shaft was #h ft4 in diameter4 ,inside there was a ladder and an elevator cage for lowering and hoisting men and the standard #a-yd4 tunnel cars4 ,at the top1 forming the head of the ,t1 there were two standard tunnel locks4 ,,manhattan ,,shafts4 ,a permanent shaft1 similar to the river shafts in ,long ,island ,city1 was constructed at ,manhattan over each pair of tunnels4 ,each shaft was located across two lines1 with its longer axis transverse to the tunnels4 ,plate ,,xiii shows their relative positions4 ,they were divided equally by a reinforced concrete partition wall transverse to the line of the tunnels4 ,on completion1 the western portions were turned over to the contractor for the cross-town tunnels for his exclusive use4 ,south ,shaft4--,work on the south shaft was started on ,june #ith1 #aijd1 with the sinking of a #af by #af-;ft4 test pit in the center of the south half of the south shaft1 which reached disintegrated rock at a depth of about #bj ft4 ,starting in ,august1 the full shaft area1 #gd by #dj ft41 was taken out in an open untimbered cut to the rock1 and a #bj by #ej-;ft4 shaft was sunk through the rock to tunnel grade1 leaving a #aj or #ab-;ft4 berm around it4 7,fig4 #a1 ,plate ,,lxx47 ,the erection of the caisson was started1 about the middle of ,january1 on the rock berm surrounding the #bj by #ej-;ft4 shaft and about #ae ft4 below the surface4 ,fig4 #c1 ,plate ,,lxiv1 shows the cutting edge of the caisson assembled4 ,the excavation of the small shaft had shown that hard rock and only a very small quantity of water would be encountered1 and that the caisson need be sunk only a short distance below the rock surface4 ,therefore1 no working-chamber roof was provided1 the caisson was built to a height of only #dj ft41 and the circular openings were permanently closed4 ,the assembling of the caisson took #b-a_/b months1 and on ,april #b;d lowering was started4 ,inverted brackets were bolted temporarily to the cutting-edge stiffening brackets1 and the sinking was carried on by methods similar to those used at ,long ,island4 ,the jacks and blocking supporting the caisson are shown in ,fig4 #d1 ,plate ,,lxiv4 ,as soon as the cutting edge entered the rock1 which was drilled about #f in4 outside of the neat lines1 the space surrounding the caisson was back-filled with clay and muck to steady it and provide skin friction4 ,as the friction increased1 the walls were filled with concrete1 and as the caisson slowly settled1 it was checked and guided by blocking4 ,the cutting edge finally came to rest #ca ft4 below mean high water1 the sinking having been accomplished in about seven weeks1 at an average rate of #j4ej ft4 per day4 ,the final position of the cutting edge in relation to its designed position is shown in ,table #a4 ,a berm about #d ft4 wide was left at the foot of the caisson below which the rock was somewhat fissured and required timbering4 ,the cutting edge of the caisson was sealed to the rock with grout on the outside and a concrete base to the caisson walls on the inside1 the latter resting on the #d-;ft4 berm4 ,following the completion of the shaft1 the permanent sump was excavated to grade for use during construction4 ,north ,shaft4--,the north shaft had to be sunk in a very restricted area4 ,the east side of the caisson cleared an adjoining building at one point by only #a ft41 while the northwest corner was within the same distance of the east line of ,first ,avenue4 ,as in the case of the ,long ,island shafts1 the steelwork for only the lower #dj ft4 was ordered at the start4 ,this height was completely assembled before sinking was begun4 ,the caisson was lowered in about the same manner as those previously described4 ,the bearing brackets for the hydraulic jacks were attached1 as at the south shaft1 to the inside of the cutting-edge brackets4 ,the east side of the caisson was in contact with the foundations of the neighboring building1 while the west side was in much softer material4 ,as a consequence1 the west side tended to settle more rapidly and thus throw the caisson out of level and position4 ,to counteract that tendency1 it was necessary to load the east wall heavily with cast-iron tunnel sections1 in addition to the concrete filling in the walls4 ,soon after sinking was begun1 a small test shaft was sunk to a point below the elevation of the top of the tunnels4 ,the rock was found to be sound1 hard1 and nearly dry4 ,it was then decided to stop the caisson as soon as a foundation could be secured on sound rock4 ,the latter was found at a depth of #ch ft4 below mean high water4 ,with the cutting edge seated at that depth1 the top of the caisson was only #b ft4 above mean high water1 and as this was insufficient protection against high tides1 a #aj-;ft4 extension was ordered for the top4 ,work1 however1 went on without delay on the remainder of the excavation4 ,the junction between the cutting edge and the rock was sealed with concrete and grout4 ,the caisson was lowered at an average rate of #j4ec ft4 per day4 ,the size of the shaft below the cutting edge was #fb ft4 #g in4 by #cb ft4 ,the average rate of excavation during the sinking in soft material was #hd cu4 yd4 per day4 ,the average rate of rock excavation below the final position of the cutting edge was #abe cu4 yd4 per day4 ,there were night and day shifts1 each working #aj hours4 ,excavation in earth cost #c4if per cu4 yd41 of which #a4de was for labor and #b4ea for top charges1 etc4 ,the excavation of rock cost #h4ic per cu4 yd41 #b4hc being for labor and #f4aj for top charges4 ,the final elevations of the four corners of the cutting edge1 together with their displacement from the desired positions1 are shown in ,table #a4 ,,river ,,tunnels4 ,the four river tunnels1 between the ,manhattan and ,long ,island ,city shafts1 a distance of about #c1ijj ft41 were constructed by the shield method4 ,eight shields were erected1 one on each line in each shaft1 the four from ,manhattan working eastward to a junction near the middle of the river with the four working westward from ,long ,island ,city4 ,toward the end of the work it was evident that the shields in ,tunnels ,b1 ,c1 and ,d would meet in the soft material a short distance east of the ,blackwell's ,island ,reef if work were continued in all headings4 ,in order that the junction might be made in firm material1 work from ,manhattan in those three tunnels was suspended when the shields reached the edge of the ledge4 ,the shields in ,tunnel ,a met at a corresponding point without the suspension of work in either4 ,an average of #a1gfj ft4 of tunnel was driven from ,manhattan and #b1adb ft4 from ,long ,island ,city4 ,illustration3 ,,plate ,,lxv1 ,,fig4 #a4--,,shield ,,fitted ,,with ,,sectional ,,sliding ,,hoods ,,and ,,sliding ,,extensions ,,to ,,the ,,floors4 ,illustration3 ,,plate ,,lxv1 ,,fig4 #b4--,,shield ,,fitted ,,with ,,fixed ,,hoods ,,and ,,fixed ,,extensions ,,to ,,the ,,floors4 ,,tunnels ,,driven ,,eastward ,,from ,,manhattan4 ,materials and ,inception of ,work4--,the materials encountered are shown in the profile on ,plate ,,xiii1 and were similar in all the tunnels4 ,in general1 they were found to be about as indicated in the preliminary borings4 ,the materials met in ,tunnel ,a may be taken as typical of all4 ,from the ,manhattan shaft eastward1 in succession1 there were #abc ft4 of all-rock section1 #hg ft4 of part earth and part rock1 #gbc ft4 of all earth1 #eae ft4 of part rock and part earth1 #bia ft4 of all rock1 and #ef ft4 of part rock and part earth4 ,the rock on the ,manhattan side was ,hudson schist1 while that in the reef was ,fordham gneiss4 ,here1 as elsewhere1 they resembled each other closely2 the gneiss was slightly the harder1 but both were badly seamed and fissured4 ,wherever it was encountered in this work1 the rock surface was covered by a deposit of boulders1 gravel1 and sand1 varying in thickness from #d to #aj ft4 and averaging about #f ft4 ,the slope of the surface of the ledge on the ,manhattan side averaged about #a vertical to #d horizontal4 ,the rock near the surface was full of disintegrated seams1 and was badly broken up4 ,it was irregularly stratified1 and dipped toward the west at an angle of about #fj degrees4 ,large pieces frequently broke from the face and slid into the shield1 often exposing the sand4 ,the rock surface was very irregular1 and was covered with boulders and detached masses of rock embedded in coarse sand and gravel4 ,the sand and gravel allowed the air to escape freely4 ,by the time the shields had entirely cleared the rock1 the material in the face had changed to a fine sand1 stratified every few inches by very thin layers of chocolate-colored clayey material4 ,this is the material elsewhere referred to as quicksand4 ,as the shield advanced eastward1 the number and thickness of the layers of clay increased until the clay formed at least #bj of the entire mass1 and many of the layers were #b in4 thick4 ,at a distance of about #ddj ft4 beyond the ,manhattan ledge1 the material at the bottom of the face changed suddenly to one in which the layers of clay composed probably #ih of the whole4 ,the sand layers were not more than #a_/af in4 thick and averaged about #b in4 apart4 ,the surface of the clay rose gradually for a distance of #dj ft4 in ,tunnels ,a and ,b1 and #ajj ft4 in ,tunnels ,c and ,d1 when gravel and boulders appeared at the bottom of the shield4 ,at that time the clay composed about one-half of the face4 ,the surfaces of both the clay and gravel were irregular1 but they rose gradually4 ,after rock was encountered1 the formations of gravel and clay were roughly parallel to the rock surface4 ,as the surface of the rock rose they disappeared in order and were again encountered when the shields broke out of rock on the east side of the ,blackwell's ,island ,reef4 ,east of the reef a large quantity of coarse open sand was present in the gravel formations before the clay appeared below the top of the cutting edge4 ,in ,tunnels ,c and ,d this was especially difficult to handle4 ,it appears to be a reasonable assumption that the layer of clay was continuous across the reef4 ,wherever the clay extended above the top of the shield it reduced the escape of air materially4 ,it is doubtless largely due to this circumstance that the part-rock sections in the reef were not the most difficult portions of the work4 ,while sinking the lower portions of the shafts the tunnels were excavated eastward in the solid rock for a distance of about #fj ft41 where the rock at the top was found to be somewhat disintegrated4 ,this was as far as it was considered prudent to go with the full-sized section without air pressure4 ,at about the same time top headings were excavated westward from the shafts for a distance of #ajj ft41 and the headings were enlarged to full size for #ej ft4 ,the object was to avoid damage to the shaft and interference with the river tunnel when work was started by the contractor for the cross-town tunnel4 ,illustration3 ,,plate ,,lxvi1 ,,fig4 #a4--,,rear ,,of ,,shield ,,showing ,,complete ,,fittings4 ,illustration3 ,,plate ,,lxvi1 ,,fig4 #b4--,,shield ,,with ,,lower ,,portion ,,of ,,bulkhead ,,removed4 ,the shields were erected on timber cradles in the shaft1 and were shoved forward to the face of the excavation4 ,concrete bulkheads1 with the necessary air-locks1 were then built across the tunnels behind the shields4 ,the shields were erected before the dividing walls between the two contracts were placed4 ,rings of iron tunnel lining1 backed by timbers spanning the openings on the west side1 were erected temporarily across the shafts in order to afford a bearing for the shield jacks while shoving into the portals4 ,the movement of the shield eastward was continued in each tunnel for a distance of about #fj ft41 and the permanent cast-iron tunnel lining was erected as the shield advanced4 ,before breaking out of rock1 it was necessary to have air pressure in the tunnels4 ,this required the building of bulkheads with air-locks inside the cast-iron linings just east of the portals4 ,before erecting the bulkheads it was necessary to close the annular space between the iron tunnel lining and the rock4 ,the space at the portal was filled with a concrete wall4 ,after about twenty permanent rings had been erected in each tunnel1 two rings were pulled apart at the tail of the shield and a second masonry wall or dam was built4 ,the space between the two dams was then filled with grout4 ,to avoid the possibility of pushing the iron backward after the air pressure was on1 rings of segmental plates1 #e_/h in4 thick and #ac-g_/h in4 wide1 were inserted in eighteen circumferential joints in each tunnel between the rings as they were erected4 ,the plates contained slotted holes to match those in the segments4 ,after the rings left the shield1 the plates were driven outward1 and projected about #e in4 ,when the tunnel was grouted1 the plates were embedded4 ,the bulkheads were completed1 and the tunnels were put under air pressure on the following dates3 ,line ,d1 on ,october #eth1 #aije2 ,line ,c1 on ,november #fth1 #aije2 ,line ,b1 on ,november #beth1 #aije2 ,line ,a1 on ,december #ast1 #aije4 ,this marked the end of the preparatory period4 ,in the deepest part of the river1 near the pier-head line on the ,manhattan side1 there was only #h ft4 of natural cover over the tops of the tunnels4 ,this cover consisted of the fine sand previously described1 and it was certain that the air would escape freely from the tunnels through it4 ,to give a greater depth of cover and to check the loss of air1 the contractor prepared to cover the lines of the tunnels with blankets of clay1 which1 however1 had been provided for in the specifications4 ,permits1 as described later1 were obtained at different times from the ,secretary of ,war1 for dumping clay in varying thicknesses over the line of work4 ,the dumping for the blanket allowed under the first permit was completed in ,february1 #aijf4 ,the thickness of this blanket varied considerably1 but averaged #aj or #ab ft4 on the ,manhattan side4 ,the original blanket was of material advantage1 but the depth of clay was insufficient to stop the loss of air4 ,the essential parts of the shields in the four tunnels were exactly alike4 ,those in ,tunnels ,b and ,d1 however1 were originally fitted with sectional sliding hoods and sliding extensions to the floors of the working chambers1 as shown by ,fig4 #a1 ,plate ,,lxv4 ,the shields in ,tunnels ,a and ,c were originally fitted with fixed hoods and fixed extensions to the floors1 as shown in ,fig4 #b1 ,plate ,,lxv4 ,a full description of the shields will be found in ,mr4 ,japp's paper4 ,the shields in each pair of tunnels were advanced through the solid rock section about abreast of each other1 until test holes from the faces indicated soft ground within a few feet4 ,as the distance between the sides of the two tunnels was only #ad ft41 it was thought best to let ,tunnels ,b and ,d gain a lead of about #ajj ft4 before ,tunnels ,a and ,c opened out into soft ground1 in order that a blow from one tunnel might not extend to the other4 ,work in ,tunnel ,c was shut down on ,december #bc;d1 #aije1 after exposing sand to a depth of #c ft4 at the top1 and it remained closed for seven weeks4 ,work in ,tunnel ,a was suspended on ,september #bith1 #aije4 ,by the time ,tunnel ,b had made the required advance1 it1 together with ,tunnels ,c and ,d1 was overtaxing the capacities of the compressor plant4 ,only a little work was done in ,tunnel ,c until ,july1 #aijf1 and work in ,tunnel ,a was not resumed until ,october #bb;d1 #aijf4 ,,tunnels ,,driven ,,westward ,,from ,,long ,,island ,,city4 ,materials and ,inception of the ,work4--,the materials met in ,tunnel ,a are typical of all four tunnels4 ,from the ,long ,island shafts westward1 in succession1 there were #abd ft4 of all-rock section1 #abe ft4 of part rock and part earth section1 #bb ft4 of all-rock section1 #ef ft4 of part rock and part earth section1 #chg ft4 of all-rock section1 #gj ft4 of part earth and part rock section1 and #a1ccc ft4 of all-earth section4 ,illustration3 ,,plate ,,lxvii ,the materials passed through are indicated on ,plate ,,xiii4 ,the rock was similar to that of the ,blackwell's ,island ,reef1 and was likewise covered by a layer of sand and boulders4 ,the remainder of the soft ground was divided into three classes4 ,the first was a very fine red sand1 which occurred in a layer varying in thickness from #f ft4 to at least #ae ft4 ,it may have been much deeper above the tunnel4 ,it is the quicksand usually encountered in all deep foundations in ,new ,york ,city4 ,the following is the result of the sifting test of this sand3 ,held on ,no4 #cj sieve #j4f ,passed ,no4 #cj1 ,no4 #dj #j4d ,no4 #dj1 ,no4 #ej #j4g ,no4 #ej1 ,no4 #fj #b4d ,no4 #fj1 ,no4 #hj #ad4i ,no4 #hj1 ,no4 #ajj #ed4j ,no4 #ajj1 ,no4 #bjj #h4j ,no4 #bjj #ai4j ------ #ajj4j ,this means that grains of all but #d of it were less than #j4jjga in4 in diameter4 ,the #ai which passed the ,no4 #bjj sieve1 the grains of which were #j4jjbf in4 or less in diameter1 when observed with a microscope appeared to be perfectly clean grains of quartz2 to the eye it looked like ordinary building sand1 sharp1 and well graded from large to small grains4 ,this sand1 with a surplus of water1 was quick4 ,with the water blown out of it by air pressure1 it is stable1 stands up well1 and is very easy to work4 ,it appears to be the same as the reddish quicksand found in most deep excavations around ,new ,york ,city4 ,the second material was pronounced bull's liver by the miners as soon as it was uncovered4 ,bull's liver seems to be a common term among ,english-speaking miners the world over4 ,it is doubtful1 however1 if it is always applied to the same thing4 ,in this case it consisted of layers of blue clay and very fine red sand4 ,the clay seemed to be perfectly pure and entirely free from sand4 ,it would break easily with a clean1 almost crystalline1 fracture1 and yet it was soft and would work up easily4 ,the layers of clay varied in thickness from #a_/af in4 to #a in41 while the thickness of the sand layer varied from #a_/d in4 to several inches4 ,the sand was the same as the quicksand already described4 ,the bull's liver was ideal material in which to work a shield4 ,it stood up as well and held the air about as well as clay1 and was much easier to handle4 ,the third material was a layer of fine gray sand which was encountered in the top of all the tunnels for about #djj ft4 just east of ,blackwell's ,island ,reef4 ,it was very open1 and had grains of rather uniform size4 ,during the starting out of the tunnels from the shafts1 and for more than a year afterward1 the roof of the working chamber in the caissons and the locks previously described under the ,long ,island shafts took the place of the bulkhead across the tunnels for confining the air pressure4 ,the first work in air pressure was to remove the shield plug closing the opening in the side of the shaft4 ,this being done1 the shield was shoved through the opening1 and excavation begun4 ,at the start the shields were fitted with movable platforms1 but no hoods of any kind were placed until after the rock excavation was completed4 ,,methods ,,of ,,excavation4 ,the distribution of materials to be excavated1 as previously outlined1 divided the excavation into three distinct classes1 for which different methods had to be developed4 ,these three classes were3 ,first4--,all-rock section4 ,second4--,rock in the bottom1 earth in the top4 ,third4--,all-earth section4 ,the extent of the second and third classes was much greater than that of the first1 and they1 of course1 determined the use of the shield4 ,shields had not previously been used extensively in rock work1 either where the face was wholly or partly in rock1 and it was necessary to develop the methods by experience4 ,the specifications required that where rock was present in the bottom1 a bed of concrete should be laid in the form of a cradle on which to advance the shield4 ,all ,rock4--,at different times1 three general methods were used for excavating in all-rock sections4 ,they may be called3 ,the bottom-heading method2 the full-face method2 and the center-heading method4 ,the bottom-heading method was first tried4 ,a heading1 about #h ft4 high and #ab ft4 wide1 was driven on the center line1 with its bottom as nearly as possible on the grade line of the bottom of the tunnel4 ,it was drilled in the ordinary manner by four drills mounted on two columns4 ,the face of the headings varied from #aj to #cj ft4 in advance of the cutting edge4 ,after driving the heading for about #aj ft41 the bottom was cleared out and a concrete cradle was set4 ,the width of the cradles varied1 but was generally from #h to #aj ft4 ,the excavation was enlarged to full size as the shield advanced1 the drills being mounted in the forward compartments of the shield1 as shown by ,fig4 #a1 ,plate ,,lxvii1 which represents the conditions after the opening had been cut in the bulkhead1 but before the new methods1 mentioned later1 had been developed4 ,illustration3 ,,plate ,,lxviii ,the sides and top were shot downward into the heading4 ,the area of the face remaining behind the heading was large1 and a great number of holes and several rounds were required to fire the face to advantage4 ,as soon as firing was started at the face1 the heading was completely blocked1 and operations there had to be suspended until the mucking was nearly completed4 ,the bottom-heading method was probably as good as any that could be devised for use with the shields as originally installed4 ,all the muck had to be taken from the face by hand and handled through the chutes or doors4 ,by drilling from the shield1 some muck was blasted on to the extensions of the floors and could be handled from the upper compartments4 ,at best1 however1 the shield with the closed transverse bulkhead was a serious obstacle to rapid work in rock sections4 ,the full-face method was only used where the rock was not considered safe for a heading4 ,a cut was fired at the bottom1 together with side holes1 in a manner quite similar to that adopted in the first set of holes for a bottom heading4 ,the cradle was then placed1 in lengths of either #b4e or #e ft41 after which the remainder of the face was fired in the same manner as for the bottom-heading method4 ,the closed transverse bulkhead with air-locks1 as shown in ,fig4 #a1 ,plate ,,lxvi1 was placed in the shield in the hope that it would only be necessary to maintain the full air pressure in the working compartments in front of the bulkhead4 ,it was also thought that some form of bulkhead which could be closed quickly and tightly would be necessary to prevent flooding the tunnel in case of blows4 ,while no attempt was ever made to reduce the pressure behind the shield bulkhead1 it was obvious from the experience with ,tunnels ,b and ,d1 while working in the sand between ,manhattan and the reef1 that the plan was not practicable1 and that the closed bulkhead in the bottom was a hindrance instead of a safeguard4 ,as soon as rock was encountered in those tunnels at the west edge of the reef1 the contractor cut through the bulkheads and altered them1 as shown in ,fig4 #b1 ,plate ,,lxvi4 ,taking advantage of the experience gained1 openings were cut through the bulkheads in ,shields ,a and ,c1 while they were shut down near the edge of the ,manhattan ledge4 ,in erecting the shields at ,long ,island ,city in ,may and ,june1 #aijf1 openings were also provided4 ,these shields had to pass through about #gjj ft4 of rock at the start1 the greater portion of which was all-rock section4 ,it was at that point that openings were first used extensively and methods were developed1 which would not have been possible except where ears could be passed through the shield4 ,the bottom-heading method was first tried1 but the working space in front of the shield was cramped1 and but few men could be employed in loading the cars4 ,to give more room1 the heading was gradually widened4 ,the enlargement at the top1 when made from the shield1 blocked all work at the face of the heading while the former operation was in progress4 ,to reduce the delays1 the heading was raised1 thus reducing the quantity of rock left in the top1 and the bottom was taken out as a bench4 ,to avoid blocking the tracks when firing the top1 a heavy timber platform was built out from the floors of the middle working compartments4 ,most of the muck from the top was caught on the platform and dropped into cars below4 ,this method of working is shown by ,fig4 #b1 ,plate ,,lxvii4 ,the platforms were not entirely satisfactory1 and1 later1 the drills in the heading were turned upward and a top bench was also drilled and fired1 as shown by ,fig4 #c1 ,plate ,,lxvii4 ,there was then so little excavation left in the top that the muck was allowed to fall on the tracks and was quickly cleared away4 ,the method just outlined is called the center-heading method1 and was the most satisfactory plan devised for full-rock sections4 ,excavation in ,part ,rock and ,part ,earth4--,this was probably the most difficult work encountered1 particularly when the rock was covered with boulders and coarse sharp sand which permitted a free escape of air4 ,it was necessary1 before removing the rock immediately under the soft ground1 to excavate the earth in advance of the shield to a point beyond where the rock was to be disturbed1 and to support1 in some way1 the roof1 sides1 and face of the opening thus made4 ,the hoods were designed mainly for the purpose of supporting the roof and the sides4 ,with the fixed hood it was necessary either to excavate for the distance of the desired shove in front of it or else to force the hood into the undisturbed material4 ,to avoid this difficulty1 the sliding hoods were tried as an experiment4 ,in using the sliding hood1 which will be described in detail in ,mr4 ,japp's paper1 the segments commencing at the top were forced forward by the screw rod1 one at a time1 as far as possible into the undisturbed material4 ,just enough material was then removed from underneath and in front of the section to free it1 and it was again forced forward4 ,these operations were repeated until the section had been extended far enough for a shove4 ,as soon as two or three sections had been pushed forward in this way1 the face near the advance end of the sliding hood was protected by a breast board set on edge and braced from the face4 ,gradually1 all the segments were worked forward1 and1 at the same time1 the whole soft ground face was sheeted with timber4 ,at times polings were placed over the extended segments in order to make room for a second shove1 as shown on ,plate ,,lxviii4 ,when the shield was advanced the nuts on the screw rods were loosened and the sections of the hoods were telescoped on to the shield4 ,the idea was ingenious1 but proved impracticable1 because of the unequal relative movements of the top and bottom of the shield in shoving1 bringing transverse strains on the hood sections4 ,illustration3 ,,plate ,,lxix ,with the fixed hood1 poling boards were used to support the roof and sides1 and the face was supported in the manner described for the sliding hoods4 ,the polings were usually maple or oak planks1 #b in4 thick1 about #h in4 wide1 and #f-a_/b ft4 long4 ,in advancing the face1 the top board of the old breast was first removed1 then the material was carefully worked out for the length of the poling4 ,the latter was then placed1 with the rear end resting over the hood and the forward end forced as far as possible into the undisturbed material4 ,when two or three polings had been placed1 a breast board was set4 ,after several polings were in position1 their forward ends were supported by some form a cantilever attached to the hood4 ,plate ,,lxix shows one kind of supports4 ,in this way all the soft material was excavated down to the rock surface1 and the roof1 sides1 and face were sheeted with timber4 ,in shoving1 the polings in the roof and sides were lost4 ,it was found that the breast could usually be advanced #e ft4 with safety4 ,the fixed hood made it possible to set the face about #g or #h ft4 in front of the cutting edge without increasing the length of the polings4 ,this distance was ample for two shoves1 and was generally adopted1 although a great many faces were set for one shove only4 ,fixed hoods were substituted for those of the sliding type1 originally placed on ,shields ,b and ,d at ,manhattan1 at about the time the latter encountered the rock at the reef4 ,in placing the polings and breasting1 all voids behind them were filled as far as possible with marsh hay or bags of sawdust or clay4 ,to prevent loss of air in open material1 the joints between the boards were plastered with clay especially prepared for the purpose in a pug mill4 ,the sliding extensions to the floors of the working compartments were often used1 in the early part of the work1 to support the timber face or loose rock1 as shown in ,fig4 #a1 ,plate ,,lxviii4 ,at such times the front of the extensions was held tightly against the planking by the pressure of the floor jacks4 ,while shoving1 the pressure on the floor jacks was gradually released1 allowing the floors to slide back into the shield and still afford support to the face4 ,the extensions also afforded convenient working platforms4 ,they were subject to severe bending strains while the shield was being shoved1 however1 and the cast-iron rams were frequently broken or jammed4 ,the extensions did not last beyond the edge of the ledge at ,manhattan1 nor more than about half through the rock work at ,long ,island ,city4 ,the fixed extensions originally placed on ,shields ,a and ,c at ,manhattan were not substantial enough1 and lasted only a few days4 ,wherever the rock face was sufficiently sound and high1 a bottom heading was driven some #bj or #cj ft4 in advance of the shield4 ,the heading was driven and the cradle placed independently of the face of the soft ground above1 and in the manner described for all-rock sections4 ,the remainder of the rock face was removed by firing top and side rounds into the bottom heading after the soft ground had been excavated4 ,great care had to be taken in firing in order not to disturb the timber work or break the rock away from under the breast boards4 ,if either occurred1 a serious run was likely to follow4 ,the bottom-heading method is shown by ,figs4 #a1 #b1 and #c1 ,plate ,,lxviii1 and the breasting and poling by ,fig4 #b1 ,plate ,,lxx4 ,in the early part of the work1 where a bottom heading was impracticable1 the soft ground was first excavated as described above1 and the rock was drilled by machines mounted on tripods1 and fired as a bench4 ,by this plan no drilling could be done until the soft ground was removed4 ,this is called the rock-bench method4 ,later the rock-cut method was devised4 ,drills were set up on columns in the bottom compartments of the shield1 and the face was drilled while work was in progress on the soft ground above4 ,the drilling was done either for a horizontal or vertical cut and side and top rounds4 ,the drillers were protected while at work by platforms of timber built out from the floors of the compartments above4 ,this plan1 while probably not quite as economical of explosives1 saved nearly all the delay due to drilling the bench4 ,illustration3 ,,plate ,,lxx1 ,,fig4 #a4--,,small ,,shaft ,,sunk ,,to ,,rock4 ,illustration3 ,,plate ,,lxx1 ,,fig4 #b4--;,,breasting ,,and ,,poling ,,in ,,front ,,of ,,shield4 ,illustration3 ,,plate ,,lxx1 ,,fig4 #c4--,,shutters ,,on ,,front ,,of ,,shield4 ,illustration3 ,,plate ,,lxx1 ,,fig4 #d4--;,,hydraulic ,,erector ,,placing ,,segment4 ,all-,earth ,section4--,as described by ,messrs4 ,hay and ,fitzmaurice1 in a paper on the ,blackwall ,tunnel1,c the contractor had used1 with marked success1 shutters in the face of the shield for excavating in loose open material4 ,he naturally adopted the method for the ,east ,river work4 ,when the shields in ,tunnels ,b and ,d1 at ,manhattan1 the first to be driven through soft ground1 reached a point under the actual bulkhead line1 work was partly suspended and shutters were put in place in the face of the top and center compartments4 ,the shutters in the center compartments in ,shield ,d are shown in ,fig4 #c1 ,plate ,,lxx1 while the method of work with the shutters is shown by ,figs4 #d1 #e1 #f1 and #g1 ,plate ,,lxviii4 ,fig4 #d on that plate shows the shield ready for a shove4 ,as the pressure was applied to the shield jacks1 men loosened the nuts on the screws holding the ends of the shutters1 and allowed the latter to slide back into the working compartments4 ,at the end of the shove1 the shutters were in the position shown in ,fig4 #e1 ,plate ,,lxviii4 ,in preparing for a new shove1 the slides in the shutters were opened1 and the material in front was raked into the shield4 ,at the same time1 the shutters were gradually worked forward4 ,the two upper shutters in a compartment were generally advanced from #ab to #ae in41 after which the muck could be shoveled out over the bottom shutters1 as shown on ,fig4 #f1 ,plate ,,lxviii1 and ,fig4 #c1 ,plate ,,lxx4 ,no shutters were placed in the bottom compartments1 and as the air pressure was not generally high enough to keep the face dry at the bottom1 these compartments were pretty well filled with the soft1 wet quicksand4 ,just before shoving1 this material was excavated to a point where it ran in faster than it could be taken out4 ,much of the excavation in the bottom compartment was done by the blow-pipe4 ,during the shove the material from the bottom compartment often ran back through the open door in the transverse bulkhead1 as shown by ,fig4 #e1 ,plate ,,lxviii4 ,in the ,blackwall ,tunnel the material was reported to have been loose enough to keep in close contact with the shutters at all times4 ,in the ,east ,river ,tunnels this was not the case4 ,the sand at the top was dry and would often stand with a vertical face for some hours4 ,in advancing the shutters1 it was difficult to bring them into close contact with the face at the end of the operation4 ,the soft material at the bottom was constantly running into the lower compartment and undermining the stiff dry material at the top4 ,the latter gradually broke away1 and1 at times1 the actual face was some feet in advance of the shutters4 ,under those circumstances1 the air escaped freely through the unprotected sand face4 ,the joints of the shutters were plastered with clay1 but this did not keep the air from passing out through the lower compartments4 ,this condition facilitated the formation of blows1 which were of constant occurrence where shutters were used in the sand4 ,in ,tunnels ,b and ,d1 at ,manhattan1 the shutters were used in the above manner clear across to the reef4 ,in ,tunnel ,c1 which was considerably behind ,tunnels ,b and ,d1 the shutters1 although placed1 were never used against the face1 and the excavation was carried on by poling the top and breasting the face4 ,the change resulted in much better progress and fewer blows4 ,the excavation through the soft material in ,tunnel ,c had just been completed when ,tunnel ,a was started1 and the gangs of workmen were exchanged4 ,the work in soft ground in ,tunnel ,a thus gained the benefit of the experience in ,tunnel ,c4 ,shutters were placed only in the top compartments in this tunnel1 and1 as in ,tunnel ,c1 were never used in contact with the face4 ,the method of work is shown by ,figs4 #a1 #b1 and #c1 ,plate ,,lxxi4 ,the result was still more rapid progress in ,tunnel ,a1 and although the loss of air was fully as great in this tunnel as in the other three1 there was only one blow which caused any considerable loss of pressure4 ,in ,tunnels ,a and ,c the diaphragms in the rear of the center compartments of the lower tiers of working chambers were removed before the shields entered the soft ground4 ,the change was not of as much advantage in soft ground as in rock1 but it facilitated the removal of the soft wet sand in the bottom4 ,in ,tunnel ,a1 after encountering gravel1 a belt conveyor was suspended from the traveling stage with one end projecting through the opening into the working compartment4 ,the use of the conveyor made it possible to continue mucking at the face while the bottom plates of the iron lining were being put in place1 and resulted in a material increase in the rate of progress4 ,illustration3 ,,plate ,,lxxi ,the shutters were not placed on the ,long ,island shields at all4 ,just before the shields passed into all soft ground1 a fixed hood was attached to each4 ,the method of working in soft ground from ,long ,island ,city is illustrated by ,plate ,,lxxii4 ,the full lines at the face of the shield show the position of the earth before a shove of the shield1 and the dotted lines show the same after the shove4 ,the face was mined out to the front of the hood and breasted down to a little below the floor of the top pockets of the shield4 ,in the middle pocket the earth was allowed to take its natural slope back on the floor4 ,toward the rear of the bottom pockets it was held by stop-planks4 ,the air pressure was always about equal to the hydrostatic head at the middle of the shield1 so that the face in the upper and middle pockets was dry4 ,in the lower pockets it was wet1 and flowed under the pressure of shoving the shield4 ,by this method #d1aie lin4 ft4 of tunnel was excavated by the four ,long ,island shields in #abj days1 from ,november #ast1 #aijg1 to ,march #ast1 #aijh4 ,this was an average of #h4gd ft4 per day per shield4 ,the rate of progress1 the nature of the materials1 and the methods adopted are shown in ,table #b4 ,preparations for ,junction of ,shields4--,as previously mentioned1 the ,manhattan shields were stopped at the edge of the reef4 ,before making the final shove of those shields1 special polings were placed with unusual care4 ,the excavation was bell-shaped to receive the ,long ,island shields4 ,the arrangement of the polings is shown by ,figs4 #d and #e1 ,plate ,,lxxi4 ,after the shields were shoved into final position1 as shown at the right in ,fig4 #e1 the rear end of the polings rested over the cutting edge and allowed room for the removal of the hood4 ,after the latter had been accomplished1 the temporary bulkheads of concrete and clay bags were built as a precaution against blows when the shields were close together4 ,an #h-;in4 pipe was then driven forward through the bulkhead for distances varying from #cj to #ajj ft41 in order to check the alignment and grade between the two workings before the shields were actually shoved together4 ,the errors in the surveys were negligible1 but here1 as elsewhere1 the shields were not exactly in the desired position1 and it took careful handling to bring the cutting edges together4 ,the ,long ,island shields were driven to meet those from ,manhattan4 ,,table #b4--,,rate ,,of ,,progress1 ,,nature ,,of ,,materials1 ,,and ,,methods ,,adopted ,,in ,,construction ,,of ,,east ,,river ,,tunnels4 ,,line ,a1 ,,long ,,island4 ---------------------------------------- ----------------------------------- ,station3 ,date3 ---------------------------------------- -- ,material4 ,method4 ,from ,to ,from ,to ---------------------------------------- --------------------------------- ,all rock ,bottom heading #fici4i #figi ,aug4 #b1 '#jf,sept #be1 '#jf ,all rock ,center heading #figi #gjfd ,sept #be1 '#jf,nov4 #ba1 '#jf ,earth and rock,center heading #gjfd #gacd ,nov4 #ba1 '#jf;,dec4 #cj1 '#jf ,earth and rock,bottom heading #gacd #gahi ,dec4 #cj1 '#jf;,feb4 #ac1 '#jg ,all rock ,bottom heading #gahi #gbaa ,feb4 #ac1 '#jg;,feb4 #ba1 '#jg ,earth and rock,center heading #gbaa #gbfg ,feb4 #ba1 '#jg,mar4 #ai1 '#jg ,all rock ,center heading #gbfg #gfed ,mar4 #ai1 '#jg,sept #f1 '#jg ,earth and rock,going out of rock #gfed #ggbd ,sept #f1 '#jg,oct4 #d1 '#jg ,all earth ,soft ground #ggbd #ijeg4c ,oct4 #d1 '#jg,mar4 #bf1 '#jh ---------------------------------------- --------------------------------- ---------------------------------------- ---------------------------------- ,rate of ,number progress of ,linear in feet ,material4 days4 feet4 per day4 ,remarks ---------------------------------------- ---------------------------------- ,all rock #ed #ci4a #j4gbd ,all rock #eg #he #a4di ,earth and rock #ci #gj #a4gi ,earth and rock #de #ee #a4bb ,all rock #h #bb #b4ge ,earth and rock #bf #ef #b4ae ,all rock #aga #chg #b4bf ,earth and rock #bh #gj #b4ej ,all earth #agd #a1ccc4c #g4ff ---------------------------------------- ---------------------------------- ,,line ,b1 ,,long ,,island4 ---------------------------------------- ----------------------------------- ,station3 ,date3 ---------------------------------------- -- ,material4 ,method4 ,from ,to ,from ,to ---------------------------------------- --------------------------------- ,all rock ,bottom heading #fibi4f #gjdf ,oct4 #af1 '#jf,nov4 #bj1 '#jf ,earth and rock,bottom heading #gjdf #gaie ,nov4 #bj1 '#jf;,feb4 #bc1 '#jg ,all rock ,bottom heading #gaie #gbbe ,feb4 #bc1 '#jg,mar4 #f1 '#jg ,earth and rock,center heading #gbbe #gbfj ,mar4 #f1 '#jg,mar4 #bd1 '#jg ,all rock ,going out of rock #gbfj #gfeg ,mar4 #bd1 '#jg;,aug4 #g1 '#jg ,earth and rock,soft ground #gfeg #ggcj ,aug4 #g1 '#jg,sept #e1 '#jg ,all earth ,soft ground #ggcj #ijdi4f ,sept #e1 '#jg,mar4 #ai1 '#jh ---------------------------------------- --------------------------------- ---------------------------------------- ---------------------------------- ,rate of ,number progress of ,linear in feet ,material4 days4 feet4 per day4 ,remarks ---------------------------------------- ---------------------------------- ,all rock #ce #aaf4d #c4cc ,earth and rock #ie #adi #a4eg ,all rock #aa #cj #b4gc ,earth and rock #ah #ce #a4id ,all rock #acf #cig #b4ib ,earth and rock #bi #gc #b4eb ,all earth #aif #a1cai4f #f4gc ---------------------------------------- ---------------------------------- ,,line ,c1 ,,long ,,island4 ---------------------------------------- ----------------------------------- ,station3 ,date3 ---------------------------------------- -- ,material4 ,method4 ,from ,to ,from ,to ---------------------------------------- --------------------------------- ,all rock ,bottom heading #fhfa4i #fiic ,june #aa1 '#jf,oct4 #af1 '#jf ,earth and rock,bottom heading #fiic #gafe ,oct4 #af1 '#jf;,feb4 #g1 '#jg ,all rock ,bottom heading #gafe #gaia ,feb4 #g1 '#jg;,feb4 #ac1 '#jg ,all rock ,center heading #gaia #geha ,feb4 #ac1 '#jg;,july #bj1 '#jg ,earth and rock,going out of rock #geha #gfef ,july #bj1 '#jg;,aug4 #be1 '#jg ,all earth ,soft ground #gfef #ijdd4d ,aug4 #be1 '#jg,mar4 #ag1 '#jh ---------------------------------------- --------------------------------- ---------------------------------------- ---------------------------------- ,rate of ,number progress of ,linear in feet ,material4 days4 feet4 per day4 ,remarks ---------------------------------------- ---------------------------------- ,all rock #abg #aca4a #a4jc ,earth and rock #aad #agb #a4ea ,all rock #f #bf #d4cc ,all rock #aeg #cij #b4dh ,earth and rock #cf #ge #b4jh ,all earth #bje #a1chh4d #f4gg ---------------------------------------- ---------------------------------- ,,line ,d1 ,,long ,,island4 ---------------------------------------- ----------------------------------- ,station3 ,date3 ---------------------------------------- -- ,material4 ,method4 ,from ,to ,from ,to ---------------------------------------- --------------------------------- ,rock ,bottom heading #fhej4f #figg ,june #b1 '#jf,oct4 #bd1 '#jf ,earth and rock,bottom heading #figg #gabb ,oct4 #bd1 '#jf;,jan4 #ac1 '#jf ,all rock ,bottom heading #gabc #gbjj ,jan4 #ac1 '#jg,mar4 #c1 '#jg ,all rock ,center heading #gbjj #gegc ,mar4 #c1 '#jg;,july #aj1 '#jg ,earth and rock,going out of rock #gegc #ggfc ,july #aj1 '#jg,sept #be1 '#jg ,all earth ,soft ground #ggfc #ijch4f ,sept #be1 '#jg,mar4 #g4 '#jh ---------------------------------------- --------------------------------- ---------------------------------------- ---------------------------------- ,rate of ,number progress of ,linear in feet ,material4 days4 feet4 per day4 ,remarks ---------------------------------------- ---------------------------------- ,rock #add #abf4d #j4hg ,earth and rock #ha #ade #a4gi ,all rock #di #gh #a4ei ,all rock #abi #cgc #b4hi ,earth and rock #gg #aij #b4dg ,all earth #afd #a1bge4f #g4gh ---------------------------------------- ---------------------------------- ,,line ,a1 ,,manhattan4 ---------------------------------------- ----------------------------------- ,station3 ,date3 ---------------------------------------- -- ,material4 ,method4 ,from ,to ,from ,to ---------------------------------------- --------------------------------- ,top heading #ajhdc #ajggd ,july #bj1 '#je;,aug4 #c1 '#je ,rock ,top lift of bench#ajhdc #ajggd ,aug4 #h1 '#je;,aug4 #bc1 '#je ,bottom lift of #ajhdc #ajggd ,aug4 #cj1 '#je,sept #bg1 '#je bench ,rock ,bottom heading #ajggd #ajgba ,sept #bg1 '#je,oct4 #bc1 '#je ,bottom heading #ajggd #ajgba ,nov4 #cj1 '#je;,dec4 #bi1 '#je ,mixed ,bottom heading #ajgba #ajfii ,oct4 #bf1 '#jf,nov4 #bj1 '#jf ,mixed ,rock bench #ajfii #ajfcd ,nov4 #bj1 '#jf;,jan4 #ac1 '#jg ,earth ,poling and #ajfcd #iiaa ,jan4 #ac1 '#jg;,apr4 #ag1 '#jg breasting ,mixed ,rock cut #iiaa #icif ,apr4 #ag1 '#jg,oct4 #bd1 '#jg ,rock ,bottom heading #icif #iceh ,oct4 #bd1 '#jg,nov4 #ad1 '#jg ,rock ,center heading #iceh #ibdb ,nov4 #ad1 '#jg;,dec4 #bg1 '#jg ,rock ,bottom heading #ibdb #iaje ,dec4 #bg1 '#jg;,feb4 #bd1 '#jh ,mixed ,rock cut #iaje #ijeg ,feb4 #bd1 '#jh,mar4 #bj1 '#jh ---------------------------------------- --------------------------------- ---------------------------------------- ---------------------------------- ,rate of ,number progress of ,linear in feet ,material4 days4 feet4 per day4 ,remarks ---------------------------------------- ---------------------------------- #ad ,excavation in normal air1 and before ,rock #aeeg #fi #a4ba advance of shield4 #bh ,rock #bfee #ec #j4if ,bottom heading timbered to avoid the #bi possibility of a break4 ,mixed #be #bb #j4hh ,bottom heading timbered4 ,mixed #ed #fe #a4bj ,earth #id #gbc #g4fi ,mixed #aij #eae #b4ga ,rock #ba #ch #a4ha ,rock #df #aaf #b4eb ,rock #ei #acg #b4cb ,mixed #be #dh #a4ib ---------------------------------------- ---------------------------------- ,,line ,b1 ,,manhattan4 ---------------------------------------- ----------------------------------- ,station3 ,date3 ---------------------------------------- -- ,material4 ,method4 ,from ,to ,from ,to ---------------------------------------- --------------------------------- ,top heading #ajhce #ajghg ,july #f1 '#je;,july #bg1 '#je ,top lift of bench#ajhce #ajghg ,aug4 #c1 '#je;,aug4 #ad1 '#je ,rock ,bottom lift of bench #ajhce #ajhae ,aug4 #bf1 '#je;,aug4 #cj1 '#je ,bottom lift of bench #ajhae #ajghg ,sept #aa1 '#je,sept #bf1 '#je ,rock ,bottom heading #ajghg #ajgjj ,oct4 #bc1 '#je;,jan4 #ag1 '#jf ,mixed ,bottom heading #ajgjj #ajffd ,jan4 #ag1 '#jf;,feb4 #ab1 '#jf ,mixed ,rock bench #ajffd #ajfca ,feb4 #ab1 '#jf,mar4 #a1 '#jf ,earth ,poling and #ajfca #ajeeh ,mar4 #a1 '#jf;,apr4 #c1 '#jf breasting ,shutters in ,earth contact with #ajeeh #iiai ,apr4 #i1 '#jf,nov4 #a1 '#jf face ,mixed ,rock bench #iiai #ihdd ,nov4 #a4 '#jf;,dec4 #bi1 '#jf ,mixed ,bottom heading #ihdd #iggf ,dec1 #bi1 '#jf;,feb4 #ab1 '#jg ,mixed ,rock cut #igff #ichd ,feb4 #ab1 '#jg;,aug4 #f1 '#jg ,rock ,full face #ichd #icba ,aug4 #f1 '#jg,sept #b1 '#jg ,rock ,center ,heading #icba #ibcj ,sept #b1 '#jg,oct4 #ab1 '#jg ,rock ,bottom heading #ibcj #ijii ,oct4 #ab1 '#jg;,dec4 #f1 '#jg ,mixed ,rock cut #ijii #ijdi4f ,dec4 #f1 '#jg;,jan4 #c1 '#jh ---------------------------------------- --------------------------------- ---------------------------------------- ---------------------------------- ,rate of ,number progress of ,linear in feet ,material4 days4 feet4 per day4 ,remarks ---------------------------------------- ---------------------------------- #ba #aa ,rock #ea #dh #j4id ,excavation done in normal air and #d before advance of shield4 #ae ,rock #hf #hg #a4ja ,mixed #bf #cf #a4ch ,mixed #ag #cc #a4id ,earth #cc #gc #b4ba ,earth #bjf #fci #c4aj ,mixed #eh #ge #a4cj ,mixed #de #fh #a4ea ,mixed #age #cib #b4bd ,rock #bg #fc #b4cc ,rock #dj #ia #b4bh ,rock #ee #aca #b4ch ,mixed #bh #di4d #a4gf ---------------------------------------- ---------------------------------- ,,line ,c1 ,,manhattan4 ---------------------------------------- ----------------------------------- ,station3 ,date3 ---------------------------------------- -- ,material4 ,method4 ,from ,to ,from ,to ---------------------------------------- --------------------------------- ,top heading #ajggi4jcajgfi ,dec4 #bj1 '#jd;,dec4 #bg1 '#jd ,top heading #ajgfi #ajgbc ,jan4 #a1 '#je;,jan4 #ae1 '#je ,rock ,excavating bench #ajggi #ajgbc ,jan4 #ba1 '#je;,feb4 #bh1 '#je ,bottom heading #ajgbc #ajfgb ,mar4 #a1 '#je,mar4 #aa1 '#je ,bottom heading #ajgbc #ajgae ,oct4 #ab1 '#je,oct4 #bg1 '#je ,rock ,bottom heading #ajgae #ajffb ,nov4 #f1 '#je;,dec4 #b1 '#je ,mixed ,bottom heading #ajffb #ajfee ,dec4 #b1 '#je;,dec4 #bc1 '#je ,mixed ,bottom heading #ajfee #ajfag ,feb4 #ab1 '#jf,mar4 #bb1 '#jf ,mixed ,rock cut #ajfag #ajehe ,apr4 #b1 '#jf;,apr4 #bj1 '#jf ,mixed ,rock cut #ajehe #ajeee ,july #bg1 '#jf;,aug4 #bf1 '#jf ,earth ,breasting and #ajeee #iidj ,aug4 #bf1 '#jf;,jan4 #b1 '#jg poling ,mixed ,rock cut #iidj #ihgj ,jan4 #b1 '#jg;,feb4 #f1 '#jg ,rock ,full face #ihgj #ihfj ,feb4 #f1 '#jg;,feb4 #ab1 '#jg ,mixed ,bottom heading #ihfj #ihci ,feb4 #ab1 '#jg,mar4 #f1 '#jg ,rock ,bottom heading #ihci #ihag ,mar4 #f1 '#jg,mar4 #ae1 '#jg ,mixed ,rock cut #ihag #iefh ,mar4 #ae1 '#jg;,july #cj1 '#jg ,rock ,middle heading #iefh #idfa ,july #cj1 '#jg;,aug4 #ba1 '#jg ,mixed ,rock cut #idfa #icef ,aug4 #ba1 '#jg,oct4 #c1 '#jg ,rock ,middle heading #icef #ibgc ,oct4 #c1 '#jg,nov4 #aa1 '#jg ,mixed ,rock cut #ibgc #ijee ,nov4 #aa1 '#jg;,feb4 #ac1 '#jh ,mixed ,rock cut #ijee #ijdd4d ,feb4 #be1 '#jh,mar4 #c1 '#jh ---------------------------------------- --------------------------------- ---------------------------------------- ---------------------------------- ,rate of ,number progress of ,linear in feet ,material4 days4 feet4 per day4 ,remarks ---------------------------------------- ---------------------------------- #g ,stopped to brace portal4 ,no work done #ad from ,march #abth to ,october #aath1 #aije1 ,rock #ch #ed #j4gg except a little trimming in ,september4 #aj ,all work up to this date done in #ae normal air4 ,heading advanced to #ajfgj and bulkheaded4 ,rock #bf #ec #b4jd ,heading advanced to #ajf #dj4 ,shut ,mixed #ba #g #j4cc down in order that ,line ,d might have a lead4 ,mixed #ch #ch #a4jj ,shut down on account of air shortage4 ,mixed #ah #cb #a4gh ,shut down on account of air shortage4 ,mixed #cj #cj #a4jj ,shut down ,april #bjth to ,july #bgth1 #aijf4 ,earth #abg #fae #d4hd ,mixed #ce #gj #b4jj ,rock #f #aj #a4ff ,mixed #bb #ba #j4ie ,rock #i #bb #b4dd ,mixed #aaj #bdi #b4bf ,heading advanced to #ighb4 ,rock #di #ajg #b4ah #idce4 ,mixed #dc #ajf #b4df ,rock #ci #hc #b4ac ,mixed #id #bah #b4cb ,shut down until ,line ,d shields met4 ,mixed #f #aa #a4hc ---------------------------------------- ---------------------------------- ,,line ,d1 ,,manhattan4 ---------------------------------------- --------------------------------- ,top heading #ajggj4diajgaf ,dec4 #i1 '#jd;,jan4 #ca1 '#je ,removing bench #ajggj4diajgce ,jan4 #a1 '#je;,jan4 #bg1 '#je ,rock ,bottom heading #ajgce #ajfhj ,jan4 #cj1 '#je;,feb4 #aj1 '#je ,trimming #ajggj #ajfhj ,mar4 #bi1 '#je;,apr4 #ab1 '#je ,trimming #ajggj #ajfhj ,aug4 #ca1 '#je,sept #ai1 '#je ,rock ,bottom heading #ajfhj #ajffg ,oct4 #e1 '#je,nov4 #h1 '#je ,mixed ,bottom heading #ajffg #ajfci ,nov4 #h1 '#je;,dec4 #bc1 '#je ,sliding hood and ,mixed breasting4 ,rock #ajfbi #ajegj ,dec4 #bc1 '#je;,jan4 #bd1 '#jf bench ,earth ,poling and #ajegj #ajdfa ,jan4 #bd1 '#jf;,feb4 #bg1 '#jf breasting ,earth ,poling1 breasting#ajdfa #ajcij ,mar4 #b1 '#jf,mar4 #ca1 '#jf and shutters ,earth ,shutters #ajcij #iida ,apr4 #bj1 '#jf,sept #c1 '#jf ,mixed ,bottom bench #iida #iiag ,sept #c1 '#jf,sept #bc1 '#jf ,mixed ,bottom heading #iiag #ihej ,oct4 #b1 '#jf,nov4 #bd1 '#jf ,rock ,bottom heading #ihej #iggb ,nov4 #bd1 '#jf;,jan4 #af1 '#jg ,mixed ,bottom heading #iggb #igbg ,jan4 #af1 '#jg;,feb4 #aj1 '#jg ,mixed ,rock cut #igbg #iegb ,feb4 #aj1 '#jg;,apr4 #bc1 '#jg ,rock ,middle heading #iegb #ieeg ,apr4 #bc1 '#jg,may #aa1 '#jg ,rock ,middle heading #ieeg #idfe ,may #bc1 '#jg;,june #ag1 '#jg ,mixed ,middle heading #idfe #idda ,june #ag1 '#jg;,june #be1 '#jg ,mixed ,rock cut #idda #idjc ,june #be1 '#jg;,july #ac1 '#jg ,rock ,middle heading #idjc #ibfd ,july #ac1 '#jg,sept #ab1 '#jg ,mixed ,middle heading #ibfd #ibed ,sept #ab1 '#jg,sept #bj1 '#jg ,rock ,middle heading #ibed #ibej ,sept #bj1 '#jg,sept #ba1 '#jg ,mixed ,rock cut #ibej #ijch4ff,sept #ba1 '#jg;,jan4 #h1 '#jh ---------------------------------------- --------------------------------- ---------------------------------------- ---------------------------------- ,rate of ,number progress of ,linear in feet ,material4 days4 feet4 per day4 ,remarks ---------------------------------------- ---------------------------------- ,rock #abc #ij #j4gc ,in normal air4 ,rock #cd #ac #j4dj ,bottom heading timbered4 ,mixed #de #ch #j4hd ,mixed #cb #ei #a4hd ,earth #ca #aji #c4da ,three days' delay to set shutters in ,earth #bi #ga #b4de top4 ,shut down #bj days to permit consolidation of the river bed and to repair broken plates4 ,earth #acf #ddi #c4dj ,four days of #acf1 delay account of flood4 ,mixed #bj #bd #a4bj ,mixed #ec #fg #a4bg ,thirteen days' shut-down to put on hood4 ,rock #ec #gh #a4dg ,mixed #be #de #a4dj ,mixed #gb #aee #b4ae ,rock #ah #ae #j4hc ,rock #be #ib #c4fh ,twelve days' delay to repair cutting edge4 ,mixed #h #bd #c4jj ,mixed #ah #ch #b4aa ,rock #fa #aci #b4bh ,mixed #h #aj #a4be ,rock #a #d #d4jj ,mixed #aji #baa4cd #a4id ---------------------------------------- ---------------------------------- ,openings were made between the headings as follows3 ,tunnel ,d1 ,february #bjth1 #aijh2 ,tunnel ,b1 ,march #c;d1 #aijh2 ,tunnel ,c1 ,march #eth1 #aijh2 ,tunnel ,a1 ,march #ahth1 #aijh4 ,it was necessary to cut away the projecting floors of the working compartments before the cutting edges could be shoved together4 ,contractor's ,organization4--,tunnel operations were carried on continuously for thirteen days out of fourteen1 regular work being shut down for repairs on alternate ,sundays4 ,when the required pressure was more than #cb lb41 four gangs of laborers were employed1 each gang working two shifts of #c hours each1 with an intermission of #c hours between the shifts4 ,when the pressure was less than #cb lb41 three gangs were employed1 each gang covering #h hours1 but with an intermission of about #a_/b hour in low pressure for lunch4 ,air ,pressures ,required4--,during the greater portion of the work in soft ground1 pressure was maintained which would about balance the hydrostatic head at the axis of the tunnel4 ,this required a pressure varying from #cj to #cd lb4 per sq4 in4 above that of the atmosphere4 ,in ,tunnels ,b and ,d1 at ,manhattan1 during the work in soft ground1 pressures as high as #cg lb4 were maintained for considerable periods of time2 in the firm material near the reef #bh lb4 was often sufficient4 ,while removing the broken plates1 the pressure was raised for a short time to #db lb41 and was maintained between #cg-a_/b and #dj lb4 for a little more than one month4 ,air ,supply4--,for regular operation the contractor furnished four compressors on each side of the river1 each having a rated capacity of #e1jjj cu4 ft4 of free air per minute delivered at #ej lb4 above normal1 when running at the rate of #ajj rev4 per min4 ,an additional compressor of the same capacity was supplied on each side of the river1 in compliance with the requirement for #be excess capacity2 the additional compressors had also high-pressure air cylinders which could be connected at will1 and in which the pressure could be increased to #aej lb41 and the air used to supply rock drills1 grouting machines1 etc4 ,the entire combination on each side of the river1 therefore1 was rated at #be1jjj cu4 ft4 of free air per minute1 or a mean of #f1bej cu4 ft4 per heading4 ,its safe working capacity was not far from #bj1jjj cu4 ft4 per min4 ,the shields broke through rock surface in ,tunnels ,b1 ,c1 and ,d1 at ,manhattan1 in ,november and ,december1 #aije4 ,the consumption of air in the four tunnels soon exceeded #ae1jjj cu4 ft4 for #bd hours1 and in ,tunnel ,d1 on several occasions1 it exceeded #g1jjj cu4 ft4 for a like period4 ,blows had become frequent1 and it was evident that the air plant was inadequate for driving four tunnels at once in the open material east of the ,manhattan rock4 ,work in ,tunnel ,a1 therefore1 was not resumed1 after the suspension on ,december #bith1 for about ten months1 and ,tunnel ,c was also closed down for more than four months of the time between ,december1 #aije1 and ,july1 #aijf4 ,during this period the capacity of the plant was increased from the rated #be1jjj cu4 ft4 of free air per minute1 to #ce1jjj4 ,in ,tunnel ,d the material had gradually become firmer1 with more clay and less escape of air1 as the ,blackwell's ,island ,reef was approached1 and1 at the end of the period1 the rock surface was within #c ft4 of the top of the shield2 in ,tunnel ,b1 the rock of the reef was still a little below the shield1 but the overlying material contained a large proportion of clay and held air very well4 ,tunnel ,c was still in open material1 but1 with two lines safe and with the increased air plant1 it was deemed best to resume work in ,tunnel ,a1 which was done on ,october #bc;d1 #aijf4 ,thenceforward work was continuous in all headings until the meeting points with the ,long ,island shields were reached4 ,this period1 ,january to ,october1 #aijf1 inclusive1 was the most strenuous of the entire work1 particularly the first six months4 ,with one and1 at times1 two tunnels closed down1 the consumption of air in the headings from ,manhattan was an average of more than #bj1jjj cu4 ft4 per min4 for periods of from #cj to #fj days2 it was often more than #be1jjj cu4 ft4 for #bd hours1 with a maximum of nearly #bi1jjj cu4 ft41 and doubtless this was exceeded considerably for shorter periods4 ,on several occasions the quantity supplied to a single tunnel averaged more than #ae1jjj cu4 ft4 per min4 for #bd hours4 ,the greatest averages for #bd hours were obtained later in ,tunnel ,a1 after the resumption of work there1 and exceeded #ai1jjj cu4 ft41 but the conditions in the headings of the other lines were then so favorable that the work was carried on continuously in all4 ,the deficiency in the original plant at ,manhattan was so marked1 and the need of driving all headings from ,long ,island simultaneously so clear1 that it was decided to increase the rated capacity of the ,long ,island compressor plant to #de1djj cu4 ft4 of free air per minute1 which was #aj1djj cu4 ft4 greater than the capacity of the ,manhattan plant after the latter had been augmented4 ,illustration3 ,,plate ,,lxxii ,the earth encountered on emerging from rock1 when driving westward from ,long ,island1 was far more compact and less permeable to air than on the ,manhattan side1 but for a distance of from #djj to #fjj ft4 immediately east of the reef1 it was a clean open sand1 and1 while the shields were passing through this1 the quantity of air supplied to the four headings seldom fell below #bj1jjj cu4 ft4 per min42 it was usually more than #be1jjj cu4 ft41 with a recorded maximum of #cc1djj cu4 ft4 ,although this was greater than ever used on the ,manhattan side1 it was more uniformly distributed among the several headings1 and in none equalled the maximum observed on the ,manhattan side1 the largest having been #ab1gjj cu4 ft4 per min4 for #bd hours2 it must be remembered1 however1 that at one time only two tunnels were in progress in the bad material in the tunnels from ,manhattan4 ,from the foregoing experience1 it would seem that the plant finally furnished at ,long ,island1 having a rated capacity of #de1djj cu4 ft4 of free air per minute1 would have been a reasonable compliance with the original actual needs on the ,manhattan side and vice versa2 the plant finally developed on the ,manhattan side1 having a rated capacity of #ce1jjj cu4 ft4 of free air per minute1 would have sufficed for the ,long ,island side4 ,the total quantity of free air compressed for the supply of the working chambers of the tunnels and the ,long ,island caissons was #cd1aji1jjj1jjj cu4 ft41 and1 in addition1 #aj1fae1jjj1jjj cu4 ft4 were compressed to between #hj and #abe lb4 for power purposes1 of which at least #hj was exhausted in the compressed-air working chambers4 ,the total supply of free air to each heading while under pressure1 therefore1 averaged about #c1eej cu4 ft4 per min4 ,the quantity of air escaping during a sudden blow-out is apparently much smaller than might be supposed4 ,investigation of a number of cases1 showing large pressure losses combined with a long stretch of tunnel supplying a relatively large reservoir of air1 disclosed that a maximum loss of about #bbj1jjj cu4 ft4 of free air occurred in #aj min4 ,this averages only a little more than #ai1jjj cu4 ft4 per min41 the maximum recorded supply to one tunnel for a period of #bd hours4 ,of this quantity1 however1 probably from #cj to #dj escaped in the first #de seconds1 while the remainder was a more or less steady loss up to the time when the supply could be increased sufficiently to maintain the lowered pressure4 ,very few blows showed losses approaching this in quantity1 but the inherent inaccuracy of the observations make the foregoing figures only roughly approximate4 ,footnote ,c3 ,minutes of ,proceedings1 ,inst4 ,c4 ,e41 ,vol4 ,,cxxx1 p4 #ej4 ,,special ,,difficulties4 ,the most serious difficulties of the work came near the start4 ,in ,tunnel ,d blows and falls of sand from the face were frequent after soft ground was met in the top4 ,about six weeks after entering the full sand face1 and before the shutters had been installed1 the shield showed a decided tendency to settle1 carrying the tunnel lining down with it and resulting in a number of badly broken plates in the bottom of the rings4 ,notwithstanding the use of extremely high vertical leads1,d the sand was so soft that the settlement of the shield continued for about fifteen rings1 the maximum being nearly #i in4 below grade4 ,the hydrostatic head at mid-height of the tunnel was #cb-a_/b lb41 and the raising of the air pressure to #cg lb41 as was done at this time1 was attended with grave danger of serious blows1 on account of the recent disturbance of the natural cover by the pulling and re-driving of piles in the reconstruction of the ,long ,island ferry slips directly above4 ,it dried the face materially1 however1 and the shield began to rise again1 and had practically regained the grade when the anticipated blow-outs occurred1 culminating with the entrance of rip-rap from the river bed into the shield and the flooding of the tunnel with #d ft4 of sand and water at the forward end4 ,the escape of air was very great1 and1 as a pressure of more than #bh lb4 could not be maintained1 the face was bulkheaded and the tunnel was shut down for three weeks in order to permit the river bed to consolidate4 ,this was the most serious difficulty encountered on any part of the work1 and1 coming at the very start1 was exceedingly discouraging4 ,during the shut-down the broken plates were reinforced temporarily with steel ribs and reinforced concrete 7,fig4 #a1 ,plate ,,lxxiii7 which1 on completion of the work1 were replaced by cast-steel segments1 as described elsewhere4 ,practically1 no further movement of iron took place1 and the loss of grade caused by the settlement of the shield1 which was by far the largest that ever occurred in this work1 was not sufficient to require a change in the designed grade or alignment of the track4 ,work was resumed with the shutters in use at the face as an aid to excavation4 ,the features of extreme seriousness did not recur1 but for two months the escape of air continued to be extremely large1 an average of #ae1jjj cu4 ft4 per min4 being required on many days during this period4 ,illustration3 ,,plate ,,lxxiii1 ,,fig4 #a4--,,temporary ,,reinforcement ,,of ,,broken ,,plates ,,and ,,removal ,,of ,a ,,plate ,,in ,,sections4 ,illustration3 ,,plate ,,lxxiii1 ,,fig4 #b4--;,,heavy ,,cast-,,steel ,,patch ,,attached ,,to ,,bent ,,segment ,,of ,,cutting ,,edge4 ,illustration3 ,,plate ,,lxxiii1 ,,fig4 #c4--;,,inflow ,,of ,,soft ,,clay ,,through ,,shield4 ,illustration3 ,,plate ,,lxxiii1 ,,fig4 #d4--,,reinforcement ,,of ,,broken ,,plate ,,with ,,long ,,polt ,,and ,,twisted ,,steel ,,rods4 ,in ,tunnel ,b1 after passing out from under the bulkhead line1 in ,april1 #aijf1 the loss of air became very great1 and blow-outs were of almost daily occurrence until the end of ,june4 ,at the time of the blows the pressure in the tunnel would drop from #b to #h lb41 and it generally took some hours to raise the pressure to what it was before the blow4 ,during that time regular operations were interrupted4 ,in the latter part of ,june a permit was obtained allowing the clay blanket to be increased in thickness up to a depth of water of #bg ft4 at mean low tide4 ,the additional blanket was deposited during the latter part of ,june and early in ,july1 and almost entirely stopped the blows4 ,by the end of the month the natural clay1 previously described1 formed the greater portion of the face1 and1 from that time forward1 played an important part in reducing the quantity of air required4 ,during ,april and the early part of ,may the work was under the ferry racks of the ,long ,island ,railroad4 ,the blanket had to be placed by dumping the clay from wheel-barrows through holes in the decking4 ,in ,tunnel ,a a bottom heading had been driven #bc ft4 in advance of the face at the time work was stopped at the end of #aije4 ,during the ten months of inactivity the seams in the rock above opened4 ,the rock surface was only from #b to #d ft4 below the top of the cutting edge for a distance of about #fj ft4 ,over the rock there were large boulders embedded in sharp sand4 ,it was an exceedingly difficult operation to remove the boulders and place the polings without starting a run4 ,the open seams over the bottom heading also frequently caused trouble1 as there were numerous slides of rock from the face which broke up the breasting and allowed the soft material from above to run into the shield4 ,there were two runs of from #ej to #ge cu4 yd4 and many smaller ones4 ,footnote ,d3 ,the lead of the shield is the angular divergence of its axis from the axis of the tunnel and1 in this tunnel1 was measured as the offset in #bc ft4 ,it was called when the shield was pointed upward from grade1 and - when pointed downward4 ,,guiding ,,the ,,shields4 ,little difficulty was experienced at any time in driving the shield close to the desired line1 but it was much harder to keep it on grade4 ,in rock section1 where the cradle could be set far enough in advance to become hard before the shield was shoved over it1 there was no trouble whatever4 ,where the cradle could be placed only a very short time before it had to take the weight of the shield1 the case was quite different4 ,the shield had a tendency to settle at the cutting edge1 and when once pointed downward it was extremely difficult to change its direction4 ,it was generally accomplished by embedding railroad rails or heavy oak plank in the cradle on solid foundation4 ,this often had to be repeated several times before it was successful4 ,in soft ground it was much easier to change the direction of the shield1 but1 owing to the varying nature of the material1 it was sometimes impossible to determine in advance how the shield should be pointed4 ,it was found by experience at ,manhattan that the iron lining remained in the best position in relation to grade when the underside of the bottom of the shield at the rear end was driven on grade of the bottom of the iron1 but if the rate of progress was slow1 it was better to drive the shield a little higher4 ,in the headings from ,long ,island1 which1 as a rule1 were in soft ground1 the cutting edges of the shields were kept from #d to #h in4 higher1 with respect to the grade line1 than the rails4 ,the shields would then usually move parallel to the grade line1 though this was modified considerably by the way the mucking was done and by the stiffness of the ground at the bottom of the shield4 ,on the average1 the shields were shoved by from ten to twelve of the bottom jacks1 with a pressure of about #d1jjj lb4 per sq4 in4 ,the jacks had #i-;in4 plungers1 which made the average total force required to shove the shield #b1hjj1jjj lb4 ,in the soft ground1 where shutters were used1 all of the twenty-seven jacks were frequently used1 and on several occasions the pressure exceeded #f1jjj lb4 per sq4 in4 ,with a unit pressure of #f1jjj lb4 per sq4 in41 the total pressure on the shield with all twenty-seven jacks in operation was #e1aed tons4 ,,injuries ,,to ,,shields4 ,there were only two instances of damage to the essential structural features of the shields4 ,the most serious was in ,tunnel ,d where the cutting edge at the bottom of the shield was forced up a slightly sloping ledge of rock4 ,a bow was formed in the steel casting which was markedly increased with the next few shoves4 ,work was suspended1 and a heavy cast-steel patch1 filling out the bow1 was attached to the bent segments1 as shown in ,fig4 #b1 ,plate ,,lxxiii4 ,no further trouble was experienced with the deformed portion4 ,the other instance was in ,tunnel ,b1 from ,long ,island1 where a somewhat similar but less serious accident occurred and was treated in a like manner4 ,bulkheads4--,at ,manhattan1 bulkheads had to be built near the shafts before the tunnels could be put under pressure4 ,after #ejj ft4 of tunnel had been built on each line1 the second bulkheads were constructed4 ,the air pressure between the first and second bulkheads was then reduced to between #ae and #bj lb4 ,when the shields had been advanced for #a1ejj ft41 the third set of bulkheads was built4 ,nearly all the broken plates which were removed were located between the first and third bulkheads at ,manhattan4 ,before undertaking this operation1 the doors of the locks in the ,no4 #c bulkheads were reversed to take pressure from the west4 ,by this means it was possible to carry on the work of dismantling the shields under comparatively low pressure simultaneously with the removal of the broken plates4 ,at ,long ,island ,city the roofs of the caissons served the purpose of the ,no4 #a bulkheads4 ,two other sets of bulkheads were erected1 the first about #ejj ft4 and the second about #a1ejj ft4 from the shafts4 ,,settlement ,,at ,,surface ,,of ,,ground4 ,the driving of such portions of the river tunnels1 with earth top1 as were under the land section1 caused a settlement at the surface varying usually from #c to #f in4 ,the three-story brick building at ,no4 #dab ,east #cdth ,street required extensive repairs4 ,this building stood over the section of part earth and part rock excavation where the tunnels broke out from the ,manhattan ledge and where there were a number of runs of sand into the shield4 ,in fact1 the voids made by those runs eventually worked up to the surface and caused the pavement of the alley between the buildings to drop #d or #e ft4 over a considerable area4 ,the tunnels also passed directly under the ferry bridges and racks of the ,long ,island ,railroad at ,east #cdth ,street4 ,tunnels ,b and ,d were constantly blowing at the time1 and1 where progress was slow1 caused so much settlement that one of the racks had to be rebuilt4 ,tunnel ,a1 on the other hand1 where progress was rapid1 caused practically no settlement in the racks4 ,,clay ,,blanket4 ,as previously mentioned1 clay was dumped over the tunnels in varying depths at different times4 ,a material was required which would pack into a compact mass and would not readily erode under the influence of the tidal currents of the river and the escape of the great volumes of air which often kept the water in the vicinity of the shields in violent motion4 ,suitable clay could not be found in the immediate vicinity of the work4 ,materials from ,shooter's ,island and from ,haverstraw were tried for the purpose4 ,the ,government authorities did not approve of the former1 and the greater portion of that used came from the latter point4 ,although a number of different permits governing the work were granted1 there were three important ones4 ,the first permit allowed a blanket which roughly followed the profile of the tunnels1 with an average thickness of #aj ft4 on the ,manhattan side and somewhat less on the ,long ,island ,city side4 ,the second general permit allowed the blanket to be built up to a plane #bg ft4 below low water4 ,this proved effective in checking the tendency to blow1 but allowed considerable loss of air4 ,finally1 dumping was allowed over limited and marked areas up to a plane of #bj ft4 below low water4 ,wherever advantage was taken of this last authority1 the excessive loss of air was almost entirely stopped4 ,after all the shields had been well advanced out into the river1 the blanket behind them was dredged up1 and the clay used over again in advance of the shield4 ,soundings were taken daily over the shields1 and1 if marked erosion was found1 clay was dumped into the hole4 ,whenever a serious blow occurred1 a scowload of clay was dumped over it as soon as possible and without waiting to make soundings4 ,for the latter purposes a considerable quantity of clay was placed in storage in the ,pidgeon ,street slip at ,long ,island ,city1 and one or two bottom-dump scows were kept filled ready for emergencies4 ,mr4 ,robert ,chalmers1 who had charge of the soundings for the contractor1 states that the depressions in the blanket caused by erosion due to the escape of air were1 as a rule1 roughly circular in plan and of a curved section somewhat flat in the center4 ,satisfactory soundings were never obtained in the center of a violent blow1 but the following instance illustrates in a measure what occurred4 ,over ,tunnel ,b1 at ,station #ajbhj1 there was normally #cf ft4 of water1 #g ft4 of clay blanket1 and #bj ft4 of natural cover4 ,air was escaping at the rate of about #aj1jjj cu4 ft4 per min41 and small blows were occurring once or twice daily4 ,on ,june #bb;d1 soundings showed #ed ft4 of water4 ,a depth of #ah ft4 of the river bottom had been eroded in about two days4 ,on the next day there were taken out of the shield boulders which had almost certainly been deposited on the natural river bed4 ,clay from the blanket also came into the shields on a number of occasions during or after blows4 ,the most notable occasion was in ,september1 #aijg1 when the top of the shield in ,tunnel ,d was emerging from the east side of ,blackwell's ,island ,reef4 ,the sand in the top was very coarse and loose1 and allowed the air to escape very freely4 ,the fall of a piece of loose rock from under the breast precipitated a run of sand which was followed by clay from the blanket1 which1 in this locality1 was largely the softer redredged material4 ,mucking out the shield was in progress when the soft clay started flowing again and forced its way back into the tunnel for a distance of #bj ft41 as shown in ,fig4 #c1 ,plate ,,lxxiii4 ,ten days of careful and arduous work were required to regain control of the face and complete the shove1 on account of the heavy pressure of the plastic clay4 ,the clay blanket was of the utmost importance to the work throughout1 and it is difficult to see how the tunnels could have been driven through the soft material on the ,manhattan side without it4 ,the new material used in the blanket amounted to #bhc1dab cu4 yd41 of which #aag1hdf cu4 yd4 were removed from over the completed tunnels and redeposited in the blanket in advance of the shields4 ,a total of #hh1jei cu4 yd4 of clay was dumped over blows4 ,the total cost of placing and removing the blanket was #cjd1jef4 ,,iron ,,lining4 ,the standard cast-iron tunnel lining was of the usual tube type1 #bc ft4 in outside diameter4 ,the rings were #cj in4 wide1 and were composed of eleven segments and a key4 ,the webs of the segments were #a-a_/b in4 thick in the central portion1 increasing to #b-c_/h in4 at the roots of the flanges1 which were #aa in4 deep1 #b-a_/d in4 thick at the root1 and #a-a_/b in4 at the edge1 and were machined on all contact faces4 ,recesses were cast in the edge of the flanges1 forming a groove1 when the lining was in place1 #a-a_/b in4 deep and about #c_/h in4 wide1 to receive the caulking4 ,the bolt holes were cored in the flanges1 and the bosses facing the holes were not machined4 ,the customary grout hole was tapped in the center of each plate for a standard #a-a_/d-;in4 pipe4 ,in this work1 experience indicated that the standard pipe thread was too fine1 and that the taper was objectionable4 ,each segment weighed1 approximately1 #b1jbj lb41 and the key weighed #ebj lb41 the total weight being #i1ajb lb4 per lin4 ft4 of tunnel4 ,fig4 #a shows the details of the standard heavy lining4 ,in addition to the standard cast-iron lining1 cast-steel rings of the same dimensions were provided for use in a short stretch of the tunnel1 when passing from a rock to a soft ground foundation1 where it was anticipated that unequal settlement and consequent distortion and increase in stress might occur1 but1 aside from the small regular drop of the lining as it passed out of the tail of the shield1 no such settlement was observed4 ,two classes of lighter iron1 one with #a-;in4 web and #h-;in4 flanges and the other with #a-a_/d-;in4 web and #i-;in4 flanges--the former weighing #e1aff lb4 per lin4 ft4 of tunnel and the latter1 #f1ggf lb4--were provided for use in the land sections between ,east ,avenue and the ,long ,island ,city shafts4 ,two weights of extra heavy segments for use at the bottom of the rings were also furnished4 ,the so-called ,,xx plates had webs and flanges #a_/d in4 thicker than the standard segment and the ,,yy plates were similarly #a_/b in4 heavier4 ,the conditions under which they were used will be referred to later4 ,all the castings were of the same general type as shown by ,fig4 #a4 ,rings tapering #c_/d in4 and #a-a_/b in4 in width were used for changes in alignment and grade1 the former being used approximately at every fourth ring on the #a #cj' curves4 ,the #a-a_/b-;in4 tapers were largely used for changes in grade where it was desired to free the iron from binding on the tail of the shield4 ,still wider tapers would have been advantageous for quick results in this respect4 ,no lug was cast on the segments for attachment to the erector1 but in its place the gadget shown on ,fig4 #d1 ,plate ,,lxx1 was inserted in one of the pairs of bolt holes near the center of the plate1 and was held in position by the running nut at one end4 ,in the beginning it was expected that the natural shape of the rings would not show more than #a in4 of shortening of the vertical diameter2 this was slightly exceeded1 however1 the average distortion throughout the tunnels being #a-g_/af in4 ,the erectors were attached to the shield and in such a position that they were in the plane of the center of the ring to be erected when the shove was made without lead and just far enough to permit placing the segments4 ,if the shield were shoved too far1 a rare occurrence1 the erection was inconvenienced4 ,in driving with high vertical leads1 which occurred more frequently1 the disadvantage of placing the erector on the shield was more apparent4 ,under such conditions the plane of the erector's motion was acutely inclined to the plane of the ring1 and1 after placing the lower portion of the ring1 it was usually necessary to shove the shield a few inches farther in order to place the upper plates4 ,the practical effect of this action is referred to later4 ,illustration3 ,,fig4 #a4 ,at first the erection of the iron in the river tunnels interfered somewhat with the mucking operations1 but the length of time required to complete the latter was ample for the completion of the former2 and the starting of a shove was seldom postponed by reason of the non-completion of a ring4 ,after the removal of the bottom of the diaphragms1 permitting the muck cars to be run into the shield and beyond1 the two operations were carried on simultaneously without serious interference4 ,the installation of the belt conveyor for handling the soft ground spoil in ,tunnel ,a was of special benefit in this respect4 ,preparatory to the final bolt tightening of each ring as erected1 a #ae-ton draw-jack1 consisting of a small pulling-jack inserted in a light eye-bar chain1 was placed on the horizontal diameter1 and frequently the erectors were also used to boost the crown of the iron1 the object being to erect the ring truly circular4 ,before shoving1 a #a-a_/d-;in4 turn-buckle was also placed on the horizontal diameter in order to prevent the spreading of the iron1 previous to filling the void outside with grout4 ,the approach of the supports for the upper floor of the trailing platform necessitated the removal of these turnbuckles from all but the three leading rings1 but if the iron showed a tendency to continue distortion1 they were re-inserted after the passage of the trailing platform and remained until the arch of the concrete lining was placed4 ,the cost of handling and erecting the iron varied greatly at different times1 averaging1 for the river tunnels1 #c4cb per ton for the directly chargeable labor of handling and erecting1 to which must be added #g4ed for top charges4 ,the cost of repairing broken plates is included in this figure4 ,broken ,plates4--,during the construction of the river section of the tunnels1 a number of segments were found to have been broken while shoving the shield4 ,the breaks1 which with few exceptions were confined to the three or four bottom plates1 almost invariably occurred on the advanced face of the ring1 and rarely extended beyond the bottom of the flange4 ,a careful study of the breaks and of the shoving records disclosed several distinct types of fracture and three principal known causes of breakage by the shield4 ,in the first case1 the accidental intrusion of foreign material between the jack head and the iron caused the jack to take its bearings on the flange above its normal position opposite the web of the ring1 and resulted usually in the breaking out of a piece of the flange or in several radiating cracks with or without a depression of the flange4 ,these breaks were very characteristic1 and the cause was readily recognizable1 even though the intruding substance was not actually observed4 ,in the second case1 the working of a hard piece of metal1 such as a small tool1 into the annular space between the iron and the tail of the shield1 where it was caught on the bead and dragged along as the shield advanced1 was the known cause of a number of broken segments4 ,such breaks had no particular characteristic1 but were usually close above the line of travel of the lost tool or metal4 ,their cause was determined by the finding of a heavy score on the underside of the segment or the discovery of the tool wedged in the tail of the shield or lying under the broken plate when it was removed4 ,it is probable that a number of breaks ascribed to unknown causes should be placed in this class4 ,the third cause includes the largest number of breaks1 and1 while difficult to define closely1 is the most interesting4 ,broadly speaking1 the breaks resulted from the movements of the shield in relation to the position of the tunnel lining4 ,while shoving through soft ground1 it was frequently difficult to apply sufficient power to the lower jacks to complete the full shove of #cj in4 on the desired alignment4 ,the shield1 therefore1 was driven upward at the beginning of the shove1 and1 as the sand packed in front of the shield and more power was required1 it was furnished by applying the upper jacks4 ,the top of the shield was slowly pushed over1 and1 at the close of the shove1 the desired position had been obtained2 but the shield had been given a rocking motion with a decided lifting of the tail toward the close of the shove4 ,a similar lifting of the tail occurred when1 with high vertical leads1 the top of the shield was pushed over in order to place the upper plates of the ring4 ,again1 when the shield was driven above grade and it was desired to descend1 the passage of the shield over the summit produced a like effect4 ,in all these movements1 with the space between the tail of the shield and the iron packed tight with pugging1 the upward thrust of the shield tended to flatten the iron in the bottom and occasional broken plates were the result4 ,the free use of the taper rings1 placed so as to relieve the binding of the lining on the tail of the shield1 forces the tunnel to follow the variations in the grade of the shield1 but reduces greatly the injuries to the rings from this action4 ,in ,tunnel ,d1 where very high vertical leads were required through the soft sand1 combined with a marked tendency of the shield to settle1 the shield was badly cramped on the iron and dragged along it at the top4 ,the bearing of the iron on its soft foundation tended to thrust up the bottom in this case also1 as shown by the opening of the bottom cross-joints when the bolts were slackened to relieve the strain during a shove4 ,the anticipated cracks in the crown plates1 which have been more frequently observed in other tunnels1 did not occur here1 and were not found elsewhere except in one place in ,tunnel ,b where they were traced to a similar action of the shield4 ,the cracks resulting from the movements of the shield1 as briefly described above1 in this third case were not confined to any particular type1 but occurred more frequently at the extreme end of the circumferential flange than at any other point4 ,the number of broken plates occurring in the river tunnels was #cai1 or #j4db of the total number erected4 ,of these1 #eb were found and removed1 either before or immediately after a shove1 by far the greater number being broken in handling before or during erection4 ,the remaining #bfg are considered below4 ,repair of ,broken ,plates4--,on the completion of a shove1 the tail of the shield lacked about #e in4 of covering the full width of the last ring1 and the removal of a plate broken during the shove1 therefore1 would have exposed the ground at the tail of the shield4 ,with a firm material in the bottom1 this introduced no particular difficulties1 and1 under such conditions1 a broken plate was usually removed at once4 ,in the sand1 however1 and especially on the ,manhattan side where it was quick and flowing1 the removal of a plate was attended with some danger1 and such plates were usually left to be removed on the completion of the tunnel4 ,many of these had been reinforced by the use of ,,xx1 ,,yy1 and steel segments placed adjacent to the break in the following rings4 ,after the meeting of the shields1 the postponed replacement of the broken segments was taken up4 ,the pressure was raised sufficiently to dry thoroughly the sand outside the segments1 which were drilled and broken out usually in quarters as shown on ,fig4 #a1 ,plate ,,lxxiii4 ,a steel segment was then inserted in the ring and drawn into place by turnbuckles4 ,the application of the draw-jack1 with a pull of about #cj tons to each end successively1 brought the plate to a firm bearing on the radial joints at the ends4 ,where the broken plate was isolated and was reinforced by steel or extra heavy segments in the adjacent ring1 the crack1 if slight1 was simply caulked to insure water-tightness4 ,if1 however1 the crack was opened or extended to the web of the plate1 the cross-flanges were tied together by a #a-a_/b-;in4 by #g-;ft4 bolt1 inserted through the bolt holes nearest the broken flange4 ,the long bolt acted in the nature of a bow string1 and was provided at its ends with two nuts set on opposite sides of the cross-joints to replace the standard bolts removed for its insertion4 ,fig4 #d1 ,plate ,,lxxiii shows one of these bolts in place4 ,in addition1 all broken plates remaining in the tunnel were reinforced with #a-;in4 twisted-steel rods in the concrete lining1 also shown in ,fig4 #d1 ,plate ,,lxxiii4 ,special ,construction at ,river ,shield ,junctions4--,dismantling the shields was started as soon as they came to rest in their final position with the cutting edges together4 ,the plans contemplated their entire removal1 with the exception of the cylindrical skins and cast-steel cutting edges4 ,inside the former the standard tunnel lining was erected to within #d ft4 of the heels of the cutting edges4 ,spanning the latter1 and forming the continuous metal tunnel lining1 the special construction shown by ,fig4 #b was built4 ,this consisted of a #a-a_/d in4 rolled-steel ring1 #g ft4 long1 erected inside the cutting edges1 with an annular clearance of #a in41 and two special cast-iron rings shaped to connect the rolled-steel ring with the normal lining4 ,one flange of the special cast-iron rings was of the standard type1 the other was returned #i in4 in the form of a ring1 the inside diameter of which was the same as the outside diameter of the rolled-steel ring to which it was bolted4 ,the space between the standard and special construction was of varying width at the various shields1 and was filled with a closure ring cast to the lengths determined in the field4 ,fig4 #b shows the completed construction4 ,hook-bolts1 screwed through threaded holes and buried in #a to #a ,portland cement grout ejected through similar holes1 reinforced the rolled-steel ring against external water pressure4 ,in two of the tunnels the concrete lining was carried completely through the junction1 and covered the whole construction1 while in the remaining two tunnels it was omitted at the rolled-steel ring1 leaving the latter exposed and set back about #c in4 from the face of the concrete4 ,illustration3 ,,fig4 #b4 ,,grouting4 ,except as previously noted1 the voids outside of the tunnel lining were filled with grout ejected through the grout holes in each segment4 ,the possibility was always present that ,portland cement1 if used for grout in the shield-driven tunnels1 would flow forward around the shield and set hard1 freezing the shield to the rock or the iron lining1 or at least forming excrescences upon it1 which would render its control difficult4 ,with this in mind1 the contractors proposed to substitute an ,english ,blue ,lias lime as a grouting material4 ,grout of fresh ,english lime containing a moderate quantity of water set very rapidly in air to the consistency of chalk4 ,its hydraulic properties1 however1 were feeble1 and in the presence of an excess of water it remained at the consistency of soft mud4 ,it was not suitable1 therefore1 as a supporting material for the tunnel4 ,an ,american lime1 made in imitation of the ,lias lime1 but having greater hydraulic properties1 was tried1 but proved unsatisfactory4 ,two brands of natural cement were also tried and rejected1 but a modified quick-setting natural cement1 manufactured especially for this work1 was eventually made satisfactory1 and by far the largest part of the river-tunnel grouting was done with this material mixed #a to #a by volume4 ,east of the ,long ,island shafts the work which was built without shields was grouted principally with ,portland cement and sand mixed #a to #a by volume4 ,in the river tunnels large quantities of the ,english lime were used neat as grout over the top of the tunnel in attempts to stop losses of air through the soft ground4 ,it was not of great efficiency1 however1 in this respect until the voids outside of the lining had been filled above the crown4 ,its properties of swelling and quick setting in the dry sand at that point then became of value4 ,the use of dry lime in the face1 where the escaping air would carry it into the voids of the sand and choke them1 was much more promptly efficacious in checking the loss4 ,with the exception of the ,english lime1 all grout was mixed #a to #a with sand in a ,cockburn continuous-stirring machine operated by a #c-;cylinder air engine4 ,the grout machine was placed on the lower floor of the trailing platform shown on ,plate ,,lxxii1 while the materials were placed on the upper platform1 and1 together with the water1 were fed into the machine through a hole in the upper floor4 ,the sand was bagged in the yard1 and the cars on which the materials were sent into the tunnels were lifted by an elevator to the level of the upper floor of the trailing platform before unloading4 ,great difficulty was experienced in preventing the waste of the fluid grout ahead of the shield and into the tail through the space between it and the iron lining4 ,in a full soft ground section1 the first condition did not usually arise4 ,in the full-rock sections the most efficient method of checking the waste was found to be the construction of dams or bulkheads outside the lining between it and the rock surface4 ,for this purpose1 at intervals of about #cj ft41 the leading ring and the upper half of the preceding one were disconnected and pulled forward sufficiently to give access to the exterior4 ,a rough dam of rubble1 or bags of mortar or clay1 was then constructed outside the iron1 and the rings were shoved back and connected up4 ,in sections containing both rock and soft ground1 grout dams were built at the cutting edge at intervals1 and were carried up as high as circumstances permitted4 ,the annular space at the tail of the shield was at all times supposed to be packed tight with clay and empty bags1 but the pugging was difficult to maintain against the pressure of the grout4 ,for a time1 #a_/b-;in4 segmental steel plates1 slipped down between the jackets and the iron1 were used to retain the pugging1 but their displacement resulted in a number of broken flanges1 and their use was abandoned4 ,in their place1 #b-;in4 segmental plates attached to the jack heads were substituted with more satisfactory results4 ,notwithstanding these devices1 the waste of grout at the tail was very great4 ,the soft ground material on various portions of the work acted very differently4 ,the clay and bull's liver did not cave in upon the iron lining for several hours after the shield had passed1 sometimes not for a day or more1 which permitted the space between it and the iron to be grouted4 ,the fine gray or beach sand and the quicksand closed in almost at once4 ,the quicksand has a tendency to fill in under the iron from the sides and in places to leave a cavity at about the horizontal diameter which was not filled from above1 as the sand1 being dried out by the air1 stood up fairly well and did not cave against the iron1 except where nearly horizontal at the top4 ,the total quantity of grout used on the work was equivalent in set volume to #bdi1fdg bbl4 of #a to #a ,portland cement grout1 of which #bcc1fdg bbl4 were ejected through the iron lining1 an average of #ad4ic bbl4 per lin4 ft4 ,the cost of grout ejected outside of the river tunnels was #ic cents per bbl4 for labor and #b4gg for top charges4 ,east of the ,long ,island shaft the corresponding costs were #j4fh and #a4fc1 the difference being partly due to the large percentages of work done in the normal air at the latter place4 ,,caulking ,,and ,,leakage4 ,up to ,august1 #aijg1 the joints between the segments of the cast-iron lining were caulked with iron filings and sal ammoniac1 mixed in the proportion of #djj to #a by weight4 ,with the air pressure balancing the hydrostatic head near the tunnel axis1 it was difficult to make the rust-joint caulking tight below the axis against the opposing water pressure2 this form of caulking was also injured in many places by water dripping from service pipes attached to the tunnel lining4 ,a few trials of lead wire caulked cold gave such satisfactory results that it was adopted as a substitute4 ,pneumatic hammers were used successfully on the lead caulking1 but were only used to a small extent on the rust borings1 which were mostly hand caulked4 ,immediately before placing the concrete lining1 all leaks1 whether in the rust borings or lead1 were repaired with lead1 and the remainder of the groove was filled with #a to #a ,portland cement mortar1 leaving the joints absolutely water-tight at that time4 ,the subsequent development of small seepages through the concrete would seem to indicate that the repair work should have been carried on far enough in advance of the concreting to permit the detection of secondary leaks which might develop slowly4 ,the average labor cost chargeable against the caulking was #ab cents per lin4 ft41 to which should be added #ba4h cents for top charges4 ,unfortunately1 it was necessary to place the greater part of the concrete lining in the river tunnels during the summer months when the temperature at the point of work frequently exceeded #he2 and the temperature of the concrete while setting was much higher4 ,this abnormal heat1 due to chemical action in the cement1 soon passed away1 and1 with the approach of winter1 the contraction of the concrete resulted in transverse cracks4 ,by the middle of the winter these had developed quite uniformly at the ends of each #cj-;ft4 section of concrete arch as placed1 and frequently finer cracks showed at about the center of each #cj-;ft4 section4 ,while the temperature of the concrete was falling1 a like change was taking place in the cast-iron lining1 with resulting contraction4 ,the lining had been erected in compressed air1 the temperature of which averaged about #gj in winter and higher in summer4 ,compressed air having been taken off in the summer of #aijh1 the tunnels then acquired the lower temperature of the surrounding earth1 slowly falling until mid-winter4 ,the contraction of the concrete1 firmly bedded around the flanges of the iron1 and showing cracks at fairly uniform intervals1 probably localized the small corresponding movements of the iron near the concrete cracks1 and resulted in a loosening of the caulking at these points4 ,with the advent of cold weather1 damp spots appeared in numerous places on the concrete1 and small seepages showed through quite regularly at the temperature cracks1 in some cases developing sufficiently to be called leaks4 ,only a few1 however1 were measurable in amount4 ,early in ,january small brass plugs were firmly set on opposite sides of a large number of cracks1 and caliper readings and air temperature observations were taken regularly throughout the winter and spring4 ,the widths of the cracks and the amount of leakage at them increased with each drop in temperature and decreased as the temperature rose again1 but until spring the width of the cracks did not return to the same point with each return of temperature4 ,the leakage was similar in all four tunnels1 but was largest in amount in ,tunnel ,d1 where1 at the beginning of ,february1 the ordinary flow was about #j4jjig cu4 ft4 per sec41 equivalent to #j4jjjjjcdg cu4 ft4 per sec4 per lin4 ft4 of tunnel4 ,of this amount #j4jjfe cu4 ft4 per sec4 could be accounted for at eight of the cracks showing measurable leakage1 leaving #j4jjcb cu4 ft4 per sec4 or #j4jjjjjjha cu4 ft4 per sec4 per lin4 ft4 of tunnel to be accounted for as general seepage distributed over the whole length4 ,it was not feasible to stop every leak in the tunnel1 most of which were indicated simply by damp spots on the concrete2 a rather simple method was devised1 however1 for stopping the leaks at the eight or ten places in each tunnel where water dripped from the arch or flowed down the face of the concrete4 ,the worst leak in any tunnel flowed about #j4jjbc cu4 ft4 per sec4 ,to stop these leaks1 rows of #a-;in4 holes1 at about #d-;in4 centers1 were drilled with jap drills through the concrete to the flange of the iron4 ,these rows were from #c to #ah ft4 long1 extending #a ft4 or more beyond the limits of the leak4 ,the bottoms of the holes were directly on the caulking groove and the pounding of the drill usually drove the caulking back1 so that the leak became dry or nearly so after the holes were drilled4 ,if left alone the leaks would gradually break out again in a few hours or a few days and flow more water than before4 ,they were allowed to do this1 however1 in only a few cases as experiments4 ,after the holes were drilled1 the bottom #d in4 next the flange was filled with soft neat cement mortar4 ,immediately on top of this was placed two plugs of neat cement about #b-a_/b in4 long1 which were #e or #f hours old and rather hard4 ,each was tamped in with a round caulking tool of the size of the hole driven with a sledge hammer4 ,on top of this were driven in the same way two more plugs of neat cement of the same size1 which were hard set4 ,these broke up under the blows of the hammer1 and caulked the hole tight4 ,when finished1 the tamping tool would ring as though it was in solid rock4 ,great pressure was exerted on the plastic mortar in the bottom of the hole1 which resulted in the re-caulking of the joint of the iron4 ,no further measurable leakage developed in the repaired cracks1 during a period of four months1 and the total leakage has been reduced to about #j4jjb cu4 ft4 per sec4 in each tunnel1 an average of #j4jjjjjjea cu4 ft4 per sec4 per lin4 ft4 ,,sump ,,and ,,pump ,,chambers4 ,to take care of the drainage of the tunnels1 a sump with a pump chamber above it was provided for each pair of tunnels4 ,the sumps were really short tunnels underneath the main ones and extending approximately between the center lines of the latter4 ,they were #aj ft4 #i-a_/b in4 in outside diameter and #dd ft4 long4 ,the water drops directly from the drains in the center lines of the tunnels into the sumps4 ,above the sumps and between the tunnels1 a pump chamber #ai ft4 #e in4 long was built4 ,above the end of the latter1 opposite the sump1 a cross-passage was constructed between the bench walls of the two tunnels4 ,this passage gives access from either tunnel through an opening in the floor to the pump chamber and through the latter to the sump4 ,from the preliminary borings it was thought that the sumps were located so that the entire construction would be in rock4 ,this proved to be the case on ,tunnels ,c and ,d1 but not on ,tunnels ,a and ,b4 ,the position of the rock surface in the latter is shown by ,fig4 #c4 ,after the excavation was completed in ,tunnel ,b1 ,january #ast1 #aijh1 the plates were removed from the side of the tunnel at the cross-passage1 and a drift was driven through the earth above the rock surface across to the lining of ,tunnel ,a4 ,the heading was timbered as shown by ,fig4 #c4 ,there was practically no loss of air from the drift1 but the clay blanket had been removed from over this locality and the situation caused some anxiety4 ,in order to make the heading as secure as possible1 the #bd-;in4 ,i-beams1 shown on ,fig4 #c1 were attached to the lining of the two tunnels4 ,the beams formed a support for the permanent concrete roof arch of the passage1 which was placed at once4 ,at the same time plates were removed from the bottom in ,tunnel ,b over the site of the sump1 and a heading was started on the line of the sump toward ,tunnel ,a4 ,as soon as the heading had been driven beyond the center line of the pump chamber1 a bottom heading was driven from a break-up westward in the pump chamber and a connection was made with the cross-passage4 ,the iron lining of the pump chamber was next placed1 from the cross-passage eastward4 ,the soft ground was excavated directly in advance of the lining1 and the ground was supported by polings in much the same manner as described for shield work4 ,on account of bad ground and seams of sand encountered in the rock below the level of the cross-beams1 the entire west wall of the pump chamber was placed before enlarging the sump to full size4 ,this was also judicious1 in order to support as far as possible the iron lining of the tunnels4 ,the sump was then excavated to full size4 ,the iron lining of the sump and the east wall of the pump chamber were placed as soon as possible4 ,the voids outside the iron lining of the sump and the pump chamber were filled as completely as possible with concrete1 and then thoroughly grouted4 ,finally1 the concrete lining was put in place inside of the iron4 ,as shown by ,fig4 #c1 the excavation of these chambers left a considerable portion of the iron lining of the tunnels temporarily unsupported on the lower inner quarter4 ,to guard against distortion1 a system of diagonals and struts was placed as shown4 ,the floor of the pump chamber was water-proofed with felt and pitch in a manner similar to that described for the caissons at ,long ,island ,city4 ,it was not possible to make the felt stick to the vertical walls with soft pitch1 which was the only kind that could be used in compressed air1 and1 therefore1 the surfaces were water-proofed by a wall of asphalt brick laid in pitch melting at #fj ,fahr4 ,forms were erected on the neat line1 and the space to the rock was filled with concrete making a so-called sand-wall similar to that commonly used for water-proofing with felt and pitch4 ,the bricks were then laid to a height of four or five courses4 ,the joints were filled with pitch instead of mortar4 ,sheets of tin were then placed against the face of the wall and braced from the concrete forms4 ,as much pitch as possible was then slushed between the brick and the sand-wall1 after which the concrete in the main wall was filled up to the top of the water-proofing course4 ,the tin was then withdrawn and the operation repeated4 ,this method was slow and expensive1 but gave good results4 ,ordinary pitch could not be used on account of the fumes1 which are particularly objectionable in compressed air4 ,the #fj pitch was slightly heated in the open air before using4 ,illustration3 ,,fig4 #c4 ,the sump and pump chamber on ,tunnels ,c and ,d differed from the one described only in minor details2 but1 being wholly constructed in rock1 presented fewer difficulties and permitted a complete envelope of water-proofing to be placed in the top4 ,,concrete ,,lining4 ,the placing of concrete inside the iron tube was done by an organization entirely separate from the tunneling force4 ,a mixing plant was placed in each of the five shafts4 ,the stone and sand bins discharged directly into mixers below1 which1 in turn1 discharged into steel side-dump concrete cars4 ,all concrete was placed in normal air4 ,the first step1 after the iron lining was scraped clean and washed down and all leaks were stopped1 was the placing of biats1 marked ,b on ,plate ,,lxxiv4 ,these were made up of a #f by #ab-;in4 yellow pine timber1 #ag ft4 long1 with two short lengths of the same size spliced to its ends by pieces of #ab-;in4 channels1 #c ft4 #i in4 long1 clamped upon the sides4 ,these biats were placed every #e ft4 along the tunnel in rings having side keys4 ,next1 a floor1 #ac ft4 wide1 was laid on the biats and two tracks1 of #cj-;in4 gauge and #f-a_/b-;ft4 centers1 were laid upon the floor4 ,there were three stages in the concreting4 ,fig4 #b1 ,plate ,,lxxiv1 shows the concrete in place at the end of the first1 and ,fig4 #c1 ,plate ,,lxxiv1 at the end of the second stage4 ,the complete arch above the bench walls was done in the last operation4 ,two #c by #aj-;in4 soldiers 7,,ss in ,figs4 #a and #b1 ,plate ,,lxxiv7 were fastened to each biat and braced across by two horizontal and two diagonal braces4 ,to each pair of soldiers a floor template1 ,t1 was then nailed4 ,the form for the center drain was then suspended as shown in ,fig4 #a1 ,plate ,,lxxiv4 ,three pieces of shuttering1 ,,fff1 #bj ft4 long1 were then nailed to the bottom of the soldiers4 ,one is all that would have been needed for the first concrete placed1 but it was easier to place them at this stage than later1 when there was less room4 ,three rough shutters were also nailed to the curved portion for the floor template4 ,opposite each biat1 a bracket1 bb1 was then nailed1 which carries a set of rough boards which formed the risers for the duct steps4 ,everything was then ready for concreting except that1 where refuge niches occurred1 a form for the portion of the niche below the seat was nailed to the shuttering4 ,this form is shown at ,r in ,fig4 #a1 ,plate ,,lxxiv4 ,illustration3 ,,plate ,,lxxiv ,the concrete was dumped down on each side from side-dump cars standing on the track1 and1 falling between the risers for the duct steps1 ran or was shoveled under the forms and down into the bottom4 ,the horizontal surface on each side the center drain was smoothed off with a shovel4 ,the workmen became very skillful at this1 and got a fairly smooth surface4 ,this concrete was usually placed in lengths of #de or #fj ft4 ,after setting for about #bd hours1 the brackets1 bb1 were removed1 together with the shuttering on the steps4 ,the triangular pieces1 t in ,fig4 #a1 ,plate ,,lxxiv1 were not removed until later4 ,instead1 a board was laid upon this lower step on which the duct layers could work4 ,this and the triangular piece were not removed until just before the bench concrete was placed4 ,this was important1 as otherwise the bond between the old and new concrete would be much impaired by dirt ground into the surface of the old concrete4 ,the ducts were then laid1 as shown in ,fig4 #b1 ,plate ,,lxxiv4 ,the remaining shutters for the face of the bench walls were then placed4 ,the remainder of the forms for the refuge niches1 ,,rr1 in ,fig4 #a1 ,plate ,,lxxiv1 were nailed to the shutters1 the steel beam over the niche was laid in place1 the forms for the ladders1 ,l in ,fig4 #b1 ,plate ,,lxxiv1 which occur every #be ft41 were tacked to the shutters1 the shutters and forms were given a coat of creosote oil1 and then all was ready for placing the bench concrete4 ,the specifications required a #b-;in4 mortar face to be placed on all exposed surfaces and the remainder to be smoothed with a trowel and straight-edge4 ,after about #dh hours1 the biats were blocked up on the bench1 and all forms between the bench walls below the working floor were removed4 ,the centering for the arch concrete consisted of simple #e by #c-a_/b by #e_/af-;in4 steel-angle arch ribs1 curved to the proper radius1 spaced at #e-;ft4 intervals4 ,each rib was made up of two pieces spliced together at the top4 ,two men easily handled one of these pieces4 ,after splicing1 the rib was supported by four hanger-bolts fastened to the iron lining as shown in ,fig4 #c1 ,plate ,,lxxiv4 ,in the early part of the work1 two additional bolts were used about half way up on the side between the upper and lower hanger-bolts4 ,it was soon found that by placing the strut between the tunnel lining and the crown of the rib1 these hanger-bolts could be dispensed with4 ,the lagging was of #c-;in4 dressed yellow pine1 #ab in4 wide1 and in #ae-;ft4 lengths4 ,each piece had three saw cuts on the back1 from end to end1 allowing it to be bent to the curve of the arch2 it was kept curved by an iron strap screwed to the back4 ,the arches were put in1 either in #ae1 #cj or #de-;ft4 lengths1 depending on what was ready for concrete and what could be done in one continuous working4 ,the rule was that when an arch was begun1 the work must not stop until it was finished4 ,an arch length always ended in the middle of a ring4 ,the lagging was placed to a height of about #f ft4 above the bench before any concreting was done4 ,when the concrete had been brought up to that point1 lagging was added1 one piece at a time1 just ahead of the concrete1 up to the crown1 where a space of about #ah in4 was left4 ,when the lagging had reached the upper hanger-bolts1 they were removed1 which left only the two bottom bolts fixed in the concrete4 ,most of these were unscrewed from the eye and saved1 as tin sleeves were placed around them before concreting4 ,two cast-iron eyes were lost for every #e ft4 of tunnel4 ,to place the key concrete1 a stage was set up in the middle of the floor1 and1 beginning at one end1 about #b ft4 of block lagging was placed4 ,over this1 concrete was packed1 filling the key as completely as possible4 ,this was done partly by shoveling and using a short rammer1 and partly by packing with the hands by the workmen1 who wore rubber gloves for the purpose4 ,another #b ft4 of lagging was then placed1 and the operation was repeated1 and thus working backward1 foot by foot1 the key was completed4 ,this is the usual way of keying a concrete arch1 but in this case the difficulty was increased by the flanges of the iron lining4 ,it was practically impossible to fill all parts of the pockets formed by these flanges4 ,to meet this difficulty1 provision was made for grouting any unfilled space4 ,as the concrete was being put in1 tin pipes were placed with their tops nearly touching the iron lining1 and their bottoms resting on the lagging4 ,each pocket was intended to have two of these pipes1 one to grout through and the other to act as a vent for the escape of air4 ,each center key ring had six pipes1 and each side key had eight4 ,the bottoms of the pipes were held by a single nail driven half way into the lagging4 ,this served to keep the pipes in position and to locate them after the lagging was taken down4 ,the cost of labor in the tunnels directly chargeable to concrete was #a4hj per cu4 yd4 ,the top charges1 exclusive of the cost of materials 7cement1 sand1 and stone71 amounted to #c4ib4 ,,electric ,,conduits4 ,in one bench wall of each tunnel there were fifteen openings for power cables and in the other1 between the river shafts1 there were forty openings for telephone1 telegraph1 and signal cables4 ,east of the ,long ,island shaft1 the number of the latter was reduced to twenty-four4 ,the telephone ducts were all of the four-way type4 ,the specifications required that the power ducts should have an opening of not less than #c-a_/b in41 nor more than #c-g_/h in41 and that after laying they should pass a #d-;ft4 mandrel1 #c-c_/h in4 at the leading end and #b-e_/h in4 at the other4 ,the outside dimension was limited between #e and #e-c_/h in4 ,the openings of the four-way ducts were required to be not less than #c-c_/h in41 nor more than #c-e_/h in41 and after laying to pass a #e-;ft4 mandrel1 #c-a_/d in4 at the leading end and #b-a_/b in4 at the other4 ,the outside dimensions were limited between #i and #i-a_/b in4 ,all were to be laid in #a_/d-;in4 beds of mortar4 ,the specifications were not definite as to the shape of the opening1 but those used were square with corners rounded to a radius of #c_/h in4 ,the four-ways were #c ft4 long1 and the singles1 #ah in4 ,a study of the foregoing dimensions will show that the working limits were narrow4 ,such narrow limits would not pay for the ordinary conduit line in a street1 where there is more room4 ,in the tunnel greater liberality meant either reducing the number of conduits or encroaching on the strength of the concrete tunnel lining4 ,the small difference of only #a_/h in4 in the size of the mandrel1 or a clearance of only #a_/af in4 on each side1 no doubt did increase the cost of laying somewhat1 though not as much as might at first be supposed4 ,all bottom courses were laid to a string1 in practically perfect line and grade1 and all joints were tested with mandrels which were in all openings1 and pulled forward as each piece of conduit was laid4 ,as the workmen became skillful1 the progress was excellent4 ,all costs of labor in the tunnel chargeable to duct laying amounted to #j4jci per ft4 of duct2 top charges brought this up to #j4jhc4 ,the serious problem was to guard against grout and mortar running into the duct opening through the joints from the concrete1 which was a rather wet mixture4 ,each joint was wrapped1 when laid1 with canvas1 weighing #aj oz4 per sq4 yd41 dipped in cement grout immediately before using4 ,these wraps were #f in4 wide1 and were cut long enough to go around the lap about the middle of the duct4 ,as soon as all the ducts were laid1 the entire bank was plastered over with fairly stiff mortar1 which1 when properly done1 closed all openings4 ,the plastering was not required by the specifications1 but was found by the contractor to result in a saving in ultimate cost4 ,the concrete on the two sides of the bank of ducts was bonded together by #b by #a_/h-;in4 steel bonds between the ducts1 laid across in horizontal joints4 ,both ends were split into two pieces1 #a in4 long1 one of which was turned up and the other down4 ,these bonds projected #a-a_/b in4 into the concrete on either side4 ,where the bond came opposite the risers of the duct step1 against which the ducts were laid1 recesses were provided for the projecting bond4 ,this was done by nailing to the rough shutters for the steps a form which when removed left a dove-tailed vertical groove4 ,this form was made in two pieces1 one tapering inward and the other with more taper outward4 ,as the bonds were placed1 these grooves were filled with mortar4 ,the ducts usually received their final rodding with the specification mandrel a month or more after they were laid1 after which all openings into splicing chambers were stopped by wooden plugs1 #h in4 long tapering from #c-c_/d in4 at one end to #b-c_/d in4 at the other end1 and shaped to fit the opening tightly4 ,at first the plugs were paraffined1 to keep them from swelling and breaking the ducts1 but were not successful1 as the paraffin lubricated them so that they would not stay in place4 ,they were expensive1 and there was some swelling in the best that were obtained4 ,a better plug was made by using no paraffin1 but by making six saw cuts1 three horizontal and three vertical1 in the larger end1 cutting to within about #b in4 of the smaller end4 ,the swelling of the wood was then taken up by the saw cuts and the spring of the wood4 ,the splicing chambers are at #djj-;ft4 intervals4 ,they are #f ft4 long1 #d ft4 #i in4 high1 with a width varying from #c ft4 #b in4 at the top to #a ft4 #b in4 at the bottom4