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Engineers and Geologists <br />Penetration Test for the 95% confidence level are 13 and 18. Figure 10 <br />shows the results of a similar best fit for data used or the cohesion- <br />less soil group using linear regression analysis. The value of the <br />mean for sample distribution is equal to 15.4. The standard deviation <br />is equal to 8.5 and the variance is equal to 70.4. Forty-one entries <br />were used for samples. The values obtained were correlated to <br />relative density by means of charts in Figure 7 of this report. <br />(Using the sampler energy input and a given Standard Penetration Test <br />value, a relative density can be determined for an implace soil. Using <br />this relative density,Winterkorn and Fang (reference 7), present the <br />results of nine studieson.an.g:le of internal friction vs. relative <br />density with respect to gradations and angularity of the granular soil <br />samples). The value for the angle of internal friction used in the <br />analysis is equal to 34 degrees. This value is conservative due to the <br />fact that the lower end confidence interval value obtained was used <br />for relative density determination. <br />GEOTECHNICAL ANALYSIS <br />Seepage Analysis. A Casagrande analysis using a graphical method was <br />used to determine the exit height of the phreatic surface and the rate <br />of seepage, using Gilboy's chart as presented in Harr's Ground Water <br />and See a e book (See Bibliography, Reference No. 3). Slope angle and <br />geometry of the maximum cross-section were used in conjunction with <br />ratio of 1/3 of the horizontal distance from the upstream toe to <br />the phreatic surface embankment interface to the vertical head applied. <br />This ratio and the slope angle determine an emperical coefficient for <br />further seepage analysis. Using the 100 year, 24 hour maximum water <br />level, and the 10 year, 24 hour maximum level, expected seepage values <br />were calculated assuming flow through the embankment. Seepage through <br />the foundation due to low permeability of the bedrock was neglected. <br />For the 100 year, 24 hour maximum flood the amount of seepage through <br />the embankment at the maximum section is estimated to be on the order <br />-g- <br />