. Railroad construction, theory and practice; a text-book for the use of students in colleges and technical schools, and a hand-book for the use of engineers in field and office . e oftenso nearly triangular that they may be considered as such withoutgreat error, and the volumes may be computed separately astriangular prismoids without adopting the more elaborate form 136 EAILROAD CONSTRUCTION. § 119, of computation so necessary for complicated irregular the ground is too irregular for this the best plan is tcfollow the uniform system. In computing the cut, as in Fig. 55^the left
. Railroad construction, theory and practice; a text-book for the use of students in colleges and technical schools, and a hand-book for the use of engineers in field and office . e oftenso nearly triangular that they may be considered as such withoutgreat error, and the volumes may be computed separately astriangular prismoids without adopting the more elaborate form 136 EAILROAD CONSTRUCTION. § 119, of computation so necessary for complicated irregular the ground is too irregular for this the best plan is tcfollow the uniform system. In computing the cut, as in Fig. 55^the left side would be as usual; there would be a small centercut and an ordinate of zero at a short distance to the right of thecenter. Then, ignoring the fill, and applying Eq. 56 strictly,we have two terms for the left side, one for the right, and theterm involving f6, which will be \hhi in this case, since hr=0,and the equation becomes Area(cut) = 2[^ih+yi(d-hi) -j-x^d+^bhi]. The area for fill may also be computed by a strict applicationof Eq. 50, but for Fig. 56 all distances for the left side are zeroand the elevation for the first point out is zero, d also must be f^7777m^. Fig. 56. considered as zero. Following the rule, § 107, literally, the equa-tion becomes Area(FiU) =^Xrkr^yr{o—li-;) -^Zr{o—hr) ^-i-&(o + /lr)],which reduces to {l>^ote that Xt, hr, etc., have different significations and valuesin this and in the preceding paragraphs.) The terminalpyramids illustrated in Fig. 43 are instances of side-hill workfor very short distances. Since side-hill work always impliesboth cut and fill at the same cross-section, whenever either thecut or fill disappears and the earthwork becomes wholly cut orwholly fill, that point marks the end of the side-hill work,and a cross-section should be taken at this point. § 120. EARTHWORK. 137 120. Borrow-pits. The cross-sections of borrow-pits will varynot only on account of the undulations of the surface of the
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