. Railway age . rises on a per centgrade to a maximum of 41 ft. above city datum above the tworoads mentioned, which depressed their tracks slightly to give an and Union avenue, the runoff starting a short distance east of thelatter, as already mentioned, and extending weist of Halsted masonry work is gravel concrete, the rKalnlng walls beingan equivalent 1:3:6 mixture, and the copings and bridge seats 1:2 wails averaged a foundation depth of )j ft., but where therewas a possibility of the walls being In proximity to future largebuildings, especially where the soil waii mo
. Railway age . rises on a per centgrade to a maximum of 41 ft. above city datum above the tworoads mentioned, which depressed their tracks slightly to give an and Union avenue, the runoff starting a short distance east of thelatter, as already mentioned, and extending weist of Halsted masonry work is gravel concrete, the rKalnlng walls beingan equivalent 1:3:6 mixture, and the copings and bridge seats 1:2 wails averaged a foundation depth of )j ft., but where therewas a possibility of the walls being In proximity to future largebuildings, especially where the soil waii mostly sand, safety wasassured by going down 10 ft. Piles were used only at two abutments of the I^ke Shore-Rock Island crossing are sofounded, due to the height of same, the soil conditions and thelength of the bridge span. .\lso. where the elevated railroad struc-ture crosses over the P. F. W. t C. and C. t W. I. the poor bottomand the length of span—230 ft—necessitated piling. Track 7rcrck Track. Fig. 2—Cross Section Showing Details of Entrance. It has already Ijeen mentioned that the western extension ofthe South Side Elevated Is liullt above the Chicago Junction fora part of the distance. As the map (Fig. 1) shows, this is l)e-tween Armour and Union avenues. The steel structure Is carriedon the retaining walls, which are widened, or buttressed, at thetop, wherever the steel columns occur, to furnlsli the requisite bear-ing area for the latter. The load is not sufllcient to require anyIncrease In the base dimension of the wall. interesting detail of the north wall as far west as Dearbornstreet Is a conduit for telephone, telegraph, signal and electric lightwires. It is a four-duct conduit embedded in the wall 12 in. btlowthe top, with openings at intervals of about 300 ft,, which are 12 , 24 In. deep and 48 In. long at intervals, as shown In the
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Keywords: ., bookcentury1800, bookdecade1870, bookidrailwayage44, bookyear1870
