. Railroad construction, theory and practice; a text-book for the use of students in colleges and technical schools, and a hand-book for the use of engineers in field and office . FjQ. 90,—HopsAc TuNNE Sectiqi^ TpROTJGB^ Soft Ghouni>, 234 RAILflOAD CONSTRUCTION. §200. should be practically level, with an allowance for drainage, the 3actual summit being at either end but not in the center. When the tunnel forms part of a long ascending grade, it is advisableto reduce the grade through the tunnel unless the tunnel isvery short. The additional atmospheric resistance and theidecreased adhesion
. Railroad construction, theory and practice; a text-book for the use of students in colleges and technical schools, and a hand-book for the use of engineers in field and office . FjQ. 90,—HopsAc TuNNE Sectiqi^ TpROTJGB^ Soft Ghouni>, 234 RAILflOAD CONSTRUCTION. §200. should be practically level, with an allowance for drainage, the 3actual summit being at either end but not in the center. When the tunnel forms part of a long ascending grade, it is advisableto reduce the grade through the tunnel unless the tunnel isvery short. The additional atmospheric resistance and theidecreased adhesion of the driver wheels on the damp rails in*;a tunnel will cause an engine to work very hard and still morerapidly vitiate the atmosphere until the accumulation of poison-ous gases becofnes a source of actual danger to the engineer and. \ Fig. 91. -St. Cloud Tunnel. fireman of the locomotive and of extreme discomfort to thepassengers. If the nominal ruling grade of the road weremaintained through a tunnel, the maximum resistance would befound in the tunnef. This would probably cause trains to stallthere, which would be objectionable and perhaps dangerous. 200. Lining. It is a characteristic of many kinds of rockand of all earthy material that, although they may be self-sustaining when first exposed to the atmosphere, they rapidlydisintegrate and require that the top and perhaps the ?ides andeven the bottom shall be lined to prevent caving in. In thiscountry, when timber was cheap, it was formerly framed as anarch and used as the permanent lining (see Fig. 92), but in §201. TUNNELS. 235 any such case the cross-section should be made extra largeso that a masonry lining may subsequently be placed insidethe wooden lining and thus postpone a large expense until theroad is better able to pay for the work. In very soft uns
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Keywords: ., bookauthorwebbwalt, bookcentury1900, bookdecade1920, bookyear1922
