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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />II <br />I <br />I <br />I <br />I <br /> <br />Overturning Stability - Overturning stability is considered satis- <br />factory if the tensile stress requirements at the upstream toe as <br />discussed below are met. <br /> <br />In order not to exceed the allowable tensile stress, the minimum <br />allowable compressive stress computed without internal hydrostatic <br />pressure should be determined from the following expression, which <br />takes into account the tensile strength of the concrete at lift <br />surfaces: <br /> <br />Szu <br /> <br />wh - ft <br />= <br />SF <br /> <br />Where: <br />S = <br />zu <br />w = <br />h = <br />ft = <br />SF = <br /> <br />minimum allowable compressive stress at the upstream face <br />unit weight of water <br />depth below reservoir surface <br />tensile strength of concrete at lift surfaces, and <br />safety factor (allowable values given below) <br /> <br />The limiting values are as follows: <br /> <br />o Case I, Usual Loading <br />SF = 3.0 <br /> <br />Szu must be greater than zero (no tension allowed) <br /> <br />o Case II, Unusual Loading <br />SF = 2.0 <br /> <br />o Case III, Extreme Loading <br />SF = 1.0 <br /> <br />3 - 21 <br /> <br />6819W/502OW <br />