. Principles of irrigation engineering, arid lands, water supply, storage works, dams, canals, water rights and products. rightangles. When graphically shown (Fig. 49) with length proportionalto the relative amount of pressure in each case they enable the con-struction of a simple triangle of forces which gives the direction andamount of resultant pressure. This line of resultant force should evidently fall within the baseof the portion of the dam under consideration, otherwise the struc- MASONRY DAMS 237 ture might be overturned. In the earliest dams built the thicknesswas as a rule made exce
. Principles of irrigation engineering, arid lands, water supply, storage works, dams, canals, water rights and products. rightangles. When graphically shown (Fig. 49) with length proportionalto the relative amount of pressure in each case they enable the con-struction of a simple triangle of forces which gives the direction andamount of resultant pressure. This line of resultant force should evidently fall within the baseof the portion of the dam under consideration, otherwise the struc- MASONRY DAMS 237 ture might be overturned. In the earliest dams built the thicknesswas as a rule made excessive and the resultant line fell far within thesection so that evidently there was a large waste of material. Thequestion as to where the resultant line should fall has been underdiscussion among the engineers for many years, it being primarily aquestion of the factor of safety to be used. There has finally beenadopted as more or less of a compromise a somewhat arbitrary ruleto the effect that the resulting line of pressure with the reservoir fullor empty should fall within the middle third of the base of each por-. FiG. 49.—Graphic computation of stresses in masonry dam. tion of the dam. The accompanying Fig. 49 gives graphically theanalysis of pressures of the East Park Dam of the Orland project,California, in which it is assumed that the weight of concrete is 140lb. per cubic foot, the weight of the water, lb., the weight of thesand and gravel in river bed, 100 lb. per cubic foot. The onlystresses computed were those due to the dam acting as a gravitysection. The figures given at the bottom of each portion of this sec-tion are the minimum and maximum vertical unit stresses per square 238 PRINCIPLES OF IRRIGATION ENGINEERING inch for the reservou full and empty. The general location of thisdam is given in Plate XV, Fig. B. In addition to the ordinary static pressure of the water in the fullreservoir there should also be considered in the case of dams in north-ern clim
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectirrigat, bookyear1913
