. Railroad construction. Theory and practice. A textbook for the use of students in colleges and technical schools. By Walter Loring Webb . d cutsthe surface. In general the earthwork of cut and fill terminatesin two pyramids. In Fig. -10 the pyramid vertices are at nand h^ and the bases are Ihrn and opq. The roadbed is generallywider in cut than in fill, and therefore the section Ihm and thealtitude In are generally greater than tlie section oj^q and thealtitude ^A:. When the line of intersection of the roadbed andnatural surface {nodkm) becomes perpendicular to the axis ofthe roadbed {ag) th
. Railroad construction. Theory and practice. A textbook for the use of students in colleges and technical schools. By Walter Loring Webb . d cutsthe surface. In general the earthwork of cut and fill terminatesin two pyramids. In Fig. -10 the pyramid vertices are at nand h^ and the bases are Ihrn and opq. The roadbed is generallywider in cut than in fill, and therefore the section Ihm and thealtitude In are generally greater than tlie section oj^q and thealtitude ^A:. When the line of intersection of the roadbed andnatural surface {nodkm) becomes perpendicular to the axis ofthe roadbed {ag) the pyramids become wedges whose bases arethe nearest convenient cross-sections. 60. Slopes, a. Cuttings. The required slopes for cuttingsvary from perpendicular cuts, which may be used in hard rockwhich will not disintegrate by exposure, to a slopeof perhaps 66 RAILROAD CONSTRUCTION. 60. 4 horizontal to 1 vertical in a soft material like quicksand or ina clayey soil winch flows easily when saturated. For earthymaterials a slope of 1 : 1 is the maximum allowable, and eventhis should only be used for firm material not easily affected by. Fig. 40. saturation. A slope of IJ horizontal to 1 vertical is a saferslope for average earthwork. It is a frequent blunder thatslopes in cuts are made too steep, and it results in excessive workin 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 ultimat
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