Railroad Engineering Volume 1; Instruction Paper - Softcover

Inhaltsangabe

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1915 Excerpt: ...points where the side slopes intersect the surface and then the elevation and distance from the center of points so chosen that straight lines joining these points will lie very nearly in the surface of the ground. 52. Position of Slope Stakes. The slope stakes are set where the side slopes intersect the surface. As seen by the figtire, these intersections depend on the elevation of the roadbed, which in turn depends on the depth of cut or fill. In Fig. 36 it may readily be seen that Fig. 36. in which s is the slope ratio of the side slopes, horizontal to vertical. See §48. Similarly it is seen in Fig. 37 that Fig. 37. But in each of these equations, both x and y are unknown quantities, and it is impracticable to depend on a strictly mathematical solution. The simplest method is to find by trial the location of points which will satisfy the equations. An experienced man will sometimes determine such a point in a single trial and generally the second trial will be sufficient. As a first approximation, we may note that a is at such a position that its x is ao =--b-j-sd. The added distance out to m equals the added drop times s. Assume that in Fig. 36, d = 7.7, b = 20 and s = 1.5: 1. The distance ac = 10 + (1.5 X 7.7) = 21.55. But experience will suggest that the required point m is about 8 feet lower down and therefore about (1.5 X 8) or 12 feet further out. As a first trial with the rod, the rod is placed at n, 34 feet out (21.55-f about 12), where a rod reading of s' (= 10.6) is found. Subtracting k (= 3.5) we have 7.1, the "y" of that point. Substituting this value of y in the first part of equation 37, we compute xt to be 32.2. This is the point n in Fig. 36, at a distance x" (which is less than os') from the center. This shows that ev...

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