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Tables For The Computation Of Railway & Other Earthwork
Tables For The Computation Of Railway And Other Earthwork By C L Crandall Hard Cover 1916 69 Pages
THIS object of these tables is to present a convenient aid in the Computation of Railway Earthwork. The volume is first found by the approximate method of avenging end areas, to which can be added, if desired, a correction due to the strict prismoidal formula, or a correction due to a modification of it for irregular ground. This separation reduces the labor, if both parts are computed at once, while it allows of computing only the approximate value at first, which will answer for all purposes except the final estimate, leaving the prismoidal correction to be computed at leisure on those volumes only where it is large enough to be appreciable.
The Table for " Volume by Avenging End Areas," is a table for triangular prisms, and it will give the approximate volume of triangular prismoids in cubic yards for a length of one hundred feet, between the parallel triangular ends, by taking the sum of the two numbers found with the base and altitude of each of the two end triangles as arguments. The table is thus independent of side slope, or width of roadbed, and will apply to borrow pits, trenches, etc., by dividing up the cross sections into triangles and trapezoids.
The method of dividing up the sections for three-level, five-level and irregular ground, while not essential, is believed to give the least labor in computing, either with or without tables.
The method for irregular ground is due to J. W. Davis, and was published in his Formula for R. R. Earthwork, t8)6.
The Table for " Prismoidal Corrections" is a table for triangular prismoids, and it will give the exact correction to be applied to the approximate volume found above for all solids which can be divided into triangular prismoids, having plane parallel ends, and planes or hyperbolic paraboloids for side faces. By using A. M. Wellinghton's method for irregular ground, that for the purposes of the prismoidal correction only, the ground may be called regular, the correction is easily and quickly applied, to three-level, five-level, and irregular ground. It may be noted that when either the bases or altitudes of the end triangles are equal, the correction diappears.
While quantities are only given for full feet the corrections for tenths are easily taken out from the margin without multiplication and can be added mentally with but slight increase of labor.
The Tables have been carefully recomputed in print, and it is confidently believed they are free from errors.
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