File:The theory of underdrainage (1918) (14579104348).jpg

Identifier: theoryofunderdra00schl (find matches)
Title: The theory of underdrainage
Year: 1918 (1910s)
Authors: Schlick, William Japhia, 1887- (from old catalog)
Subjects: Drainage
Publisher: Ames, Ia
Contributing Library: The Library of Congress
Digitizing Sponsor: Sloan Foundation

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diagram may be prepared by plot-ting the discharge for each size of tile at three grades and then con-necting these points with straight lines. The scales at the right of thediagram are prepared simply by platting the number of acresdrained at different rates of runoff opposite the equivalent dischargein cubic feet per second. This use of the diagram may be explained by two examples: 1. What is the discharge from a 15 inch drain at a grade of 0.20%or 0.20 feet per 100 feet? Follow up the vertical line from the notation0.20 at the bottom of the diagram till this line intersects the dis-charge line for 15 inch tile and then across horizontally to the scaleat the left, where the result is found to be approximately 2.28 cubicfeet per second. 2. What size of tile, laid at a .015% grade, will be required todrain 500 acres at a j^-inch runoff? Follow up the vertical line repre-senting a grade of .015% till this intersects the horizontal line from Discharge in Cubic Feet per Second $ § SS §
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1 ; ■ ■ ; I I I ; I I I I ; I I I I ; I I I I ; II I I ;—I ; I ; I ; I ; I ; I I I I ; ; I I I ; I I I l;IIM; I I II ,,*,*,, 5 § g § §■ g § 8 8 § 8 I 8 § 8 l I ! I ; i i i i ; I I I I ; ii I I 111 i i;—; ; I j I ; i ; i ; r t i i ; i i i i ; 11 i i(11n( i i M 2 ° ° ooooooo o 855 c> sg H fD 50 500 acres at a ^-inch runoff on the scale at the right. This intersec-tion shows that a 24 inch tile is slightly too small and a 26 inch tiletoo large. The engineer must use his judgment in deciding betweenthese two sizes, though in a case of this kind, it is often better tohave drains too large rather than too small. In designing a drainagesystem all drains should be designed to have the required capacitywhen the hydraulic grade is parallel to the constructed grade, orwhen flowing full but under no head other than that afforded by theslope of the drain. If this is done, the drain will have extra capacityfor the flow from unusual storms and spring freshets when the waterwill

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