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Darcy's Law / 91 <br /> 7 <br /> Within the elevation range considered in applied hydrology, the acceleration due to gravity may be consid- <br /> ered very nearly a constant, thus giving an almost perfect correlation between fluid potential and hydraulic <br /> head. To all intents and purposes, therefore, knowing one parameter is .as good as knowing the other, and <br /> this long (and some will say futile) review of the Bernoulli equation may be concluded the way it was <br /> introduced, with the same simple, but all-important concept that: <br /> The Potential for Water to Flow and do Work is a Function of Hydraulic Head. <br /> End of Box 4- <br /> USCS RELATIVE K = cm/sec DRAINAGE POTENTIAL FOR <br /> SYMBOL PERMEABILITY FROST HEAVE <br /> GW High > 10'2 Excellent Very Slight <br /> GP Very High > 10"' Excellent None to Very Slight <br /> GM Medium to Low 10-3 to 10-1 Fair to Poor Slight to Medium <br /> GC Medium to Very Low 10' to IC poor Medium <br /> SW Medium to High > 10.3 Good Very Slight <br /> SP High >10, Good None to Slight <br /> i <br /> SM Medium to Low 10-3 to 10 6 Fair to Poor Slight to Medium <br /> SC Low Ur to 10-' Very Poor Medium to High <br /> —� ML Low 1W to 10-6 Poor Medium to High <br /> CL Very Low 10�6 to 10' �ery Poor Medium to High <br /> OL Low <br /> 10� to 10� Poor Medium to High <br /> MH Low 10 to 1(Y6 Poor Medium to High <br /> CH Very Low 10-6 to 10-1 Practically None Medium <br /> OH Very Low 106 to 10-1 Practically None Medium <br /> PT Medium to Low (not suitable for most hydrogeologic and engineering geologic projects) <br /> Table 4-1 Hydrogeologic Properties of Soils. <br /> (based on various sources and the practical experience of the authors) <br /> fi <br />