. Railroad construction. Theory and practice . Fig. 88.—Hoosac Tunnel. Section through Soft Ground. 186 RAILROAD CONSTRUCTION. §166. actual summit being perhaps in the center so as to drain bothways. When the tunnel forms part of a long ascending grade,it is advisable to reduce the grade through the tunnel unless thetunnel is a ery short The additional atmospheric resistance andthe decreased adhesion of the dri^er wheels on the damp rails ina tunnel will cause an engine to work very hard and still morerapidly vitiate the atmosphere until the accumulation of poison-ous gases becomes a source of
. Railroad construction. Theory and practice . Fig. 88.—Hoosac Tunnel. Section through Soft Ground. 186 RAILROAD CONSTRUCTION. §166. actual summit being perhaps in the center so as to drain bothways. When the tunnel forms part of a long ascending grade,it is advisable to reduce the grade through the tunnel unless thetunnel is a ery short The additional atmospheric resistance andthe decreased adhesion of the dri^er wheels on the damp rails ina tunnel will cause an engine to work very hard and still morerapidly vitiate the atmosphere until the accumulation of poison-ous gases becomes a source of actual danger to the engineer and. 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 tunnel. This would probabl}^ cause trains to stallthere, which would be objectionable and perhaps dangerous. 166. 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 is cheap, it is occasionally framed as anarch and used as the permanent lining, but masonry is alwaysto be preferred. Frequently the cross-section is made extra §167. TUNNELS, 187 large so 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 unst
Size: 1662px × 1503px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorwebbwalt, bookcentury1900, bookdecade1900, bookyear1903
