. The elements of railroad engineering . N. ballast of 15 inches. When the tunnel lining has an invert,i. e., when the section of the floor is concave, the drain issometimes built under the track, and covered with flags toprevent clogging with ballast. Side ditches are to bepreferred, as they are always accessible and easily cleared. PROTECTION W^ORK. 1532. Classification.—Under this head will be con-sidered surface ditches, changing channels of streams^ cribwork, paving, etc. 1533. Surface Ditches.—Surface ditches are cut atthe top of slopes, but at sufficient distance from them toprevent the
. The elements of railroad engineering . N. ballast of 15 inches. When the tunnel lining has an invert,i. e., when the section of the floor is concave, the drain issometimes built under the track, and covered with flags toprevent clogging with ballast. Side ditches are to bepreferred, as they are always accessible and easily cleared. PROTECTION W^ORK. 1532. Classification.—Under this head will be con-sidered surface ditches, changing channels of streams^ cribwork, paving, etc. 1533. Surface Ditches.—Surface ditches are cut atthe top of slopes, but at sufficient distance from them toprevent the water from breaking through and washingdown the slope. Where the natural slope of the ground istowards the center line and of such a degree that a largeproportion of storm water runs off, the surface ditchesshould be cut before construction commences. When thisimportant precaution is neglected, it often occurs that agreat amount of storm water is discharged into open cuts,effectually stopping all work until the water is drained off. Fig. 455. and the ground becomes dry enough to handle. The sightof men and animals floundering in flooded cuttings is toocommon in railroad work. Many contractors, and especiallysub-contractors, are of limited experience, financially irre-sponsible, and generally follow a penny-wise policy. In suchcases, the engineer in charge must insist on such precau- RAILROAD CONSTRUCTION. 967 tions being taken as will insure a vigorous prosecution ofthe work. Ditches are usually paid for at the same priceper cubic yard as ordinary excavation. Fig. 455 shows a section of a surface ditch which will meetthe requirements of most situations. The line A B repre-sents the natural slope of the ground; C, the surface ditch;B D, the side slope of the cutting, and D E, the half widthof the roadway. The center line of the road is denoted byE F. 153-4. Changing Channels of Streams.—It fre-quently happens when the line of road is parallel to the gen-eral direction of
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectrailroadengineering
