. Railroad structures and estimates . ement ofthe train through the tunnel is said to be the best long tunnels power-driven fans are sometimes used. The ordinary wood or rock tunnel sections in common use areshown on Figs. 41 and 42, and their average cost is about asfollows: Fig. 41, Post section with lagging: Excavating 18 cubic yards per lineal foot. Timber, 450 feet B. M. per lineal foot. Cost per lineal foot $45 to $55 without track or ballast. Post section without lagging: Excavating 18 cubic yards per lineal foot. Timber 350 feet B. M. per lineal foot. Cost per lineal foot
. Railroad structures and estimates . ement ofthe train through the tunnel is said to be the best long tunnels power-driven fans are sometimes used. The ordinary wood or rock tunnel sections in common use areshown on Figs. 41 and 42, and their average cost is about asfollows: Fig. 41, Post section with lagging: Excavating 18 cubic yards per lineal foot. Timber, 450 feet B. M. per lineal foot. Cost per lineal foot $45 to $55 without track or ballast. Post section without lagging: Excavating 18 cubic yards per lineal foot. Timber 350 feet B. M. per lineal foot. Cost per lineal foot $35 to $45 without track or ballast. Fig. 42, Rock section: Excavating 14 cubic yards per lineal foot. Cost per lineal foot, $50 to $65 without track or ballast. TUNNELS. 85 Portals. — The end portals for the tunnel consist of 12X12posts spaced 2-foot centers for a distance of 8 feet from the ends,with 12Xl2 timbers built over and across the end posts, toform retaining wall on top; the end walls are also braced with Split Cordwood. Figs. 41 and 42. Tunnels. 12X12 timbers forming wing walls running parallel with thetrack at an angle of 45 degrees at one-third and two-thirds theheight with lining behind if necessary to take the end slope ofthe hill; the brace posts are secured at the bottom by extendingthe main sill. The timber in the portal as described above would be 3000 feetB. M. per foot for the last 8 feet of the tunnel at either end. The 86 RAILROAD STRUCTURES AND ESTIMATES. length of extra timbering and wing walls to form portals willvary to suit each individual case, 8 feet being the minimum. TABLE 38. — COST FIGURES FROM DRINKERS TUNNELING. Cost per cubic yard. Cost per lineal foot. Material. Excavation. Masonry. Single. Double. Single. Double. Single. Double. Hard rock $ $ $ $ $ $ Loose rock Soft ground BUILDINGS. 87 CHAPTER V. BUILDINGS. Tool Houses. In the maintenance of
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