. Railroad construction, theory and practice; a text-book for the use of students in colleges and technical schools . lvert design. In Plate IV is shownthe design for an 8-foot arch culvert according to the standardof the Norfolk and Western R. R. Note that the plan uses theflaring wing walls (Fig. 106, h) on the up-stream side (thusprotecting the abutments from scour) and straight wing walls(similar to Fig, 106, c) on the down-stream end. This econo-mizes masonry and also simplifies the constructive w^ork. Notealso the simplicity of the junction of the wing walls with thebarrel of the arch, t
. Railroad construction, theory and practice; a text-book for the use of students in colleges and technical schools . lvert design. In Plate IV is shownthe design for an 8-foot arch culvert according to the standardof the Norfolk and Western R. R. Note that the plan uses theflaring wing walls (Fig. 106, h) on the up-stream side (thusprotecting the abutments from scour) and straight wing walls(similar to Fig, 106, c) on the down-stream end. This econo-mizes masonry and also simplifies the constructive w^ork. Notealso the simplicity of the junction of the wing walls with thebarrel of the arch, there being no re-entrant angles below thespringing line of the arch. The design here shown is but oneof a set of designs for arches varying in span from 6 to 30. MINOR OPENINGS. 228. Cattle-guards, (a) Pit guards. Cattle-guards will beconsidered under the he^d of minor openings, since the old-fashioned plan of pit guards, which are even now defended and §228. CULVERTS AND MINOR BRIDGES. 261 preferred by some railroad men, requires a break in the con-tinuity of the roadbed. A pit about three feet deep, five feet. Fig. 107.—Cattle-guard with Wooden Slats. long, and as wide as the width of the roadbed, is walled up withstone (sometimes with wood), and the rails are supported onheavy timbers laid longitudinally with the rails. The break inthe continuity of the roadbed produces a disturbance in theelastic wave running through the rails, the effect of which isnoticeable at high velocities. The greatest objection, however,lies in the dangerous consequences of a derailment or a failureof the timbers owing to unobserved decay or destruction byfire—caused perhaps by sparks and cinders from passing loco-motives. The very insignificance of the structure often leadsto careless inspection. But if a single pair of wheels gets off therails and drops into the pit, a costly wreck is inevitable. (b) Surface cattle-guards. These are fastened on top of theties; the continuity of the roadbed is
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