. Railroad construction. Theory and practice. A textbook for the use of students in colleges and technical schools. By Walter Loring Webb . rkin clearing out from the ditches the material that slides down,at a much higher cost per yard than it would have cost to takeit out at first, to say nothing of the danger of accidents frompossible landslides. b. Embankments. The slopes of an embankment vary from1: 1 to : 1. A rock fill will stand at 1:1, and if some careis taken to form the larger pieces on the outside into a roughdry wall, a much steeper slope can be allowed. This method issometimes
. Railroad construction. Theory and practice. A textbook for the use of students in colleges and technical schools. By Walter Loring Webb . rkin clearing out from the ditches the material that slides down,at a much higher cost per yard than it would have cost to takeit out at first, to say nothing of the danger of accidents frompossible landslides. b. Embankments. The slopes of an embankment vary from1: 1 to : 1. A rock fill will stand at 1:1, and if some careis taken to form the larger pieces on the outside into a roughdry wall, a much steeper slope can be allowed. This method issometimes a necessity in steep side-hill work. Earthwork em-bankments generally require a slope of 1J to 1. If madesteeper at first, it generally results in the edges giving way, re-quiring repairs until the ultimate slope is nearly or quite IJ-: difficulty of incorporating the added material with the oldembankment and preventing its sliding off frequently makesthese repairs disproportionately costly. § 62. EARTIIWOIiK. 67 61. Compound sections. AVlien the cut consists partly ofearth and partly of rock, a compound cross-section must be. Fig. 41. made. If borings have been made so that tlie contour of therock surface is accurately known, then the true cross-section maybe determined. The rock and earth should be calculated sepa-rately, and this will require an accurate knowledge of where therock runs out—a difficult matter when it must be deter-mined by boring. During construction the center part of theearth cut would be taken out first and the cut widened until asufficient width of rock surface had been exposed so that therock cut would have its proper width and side slopes. Then theearth slopes could be cut down at the proper angle. A berni of about three feet is usually left on the edges of the rock cut asa margin of safety against a possible sliding of the earth sloj^ the work is done, the amount of excavation that has beenmade is readily computable, but accurate prel
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