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<br />45 <br /> <br />-~ <br /> <br />Example: Calculation Equivalent Fluid Weight Cond,ition One <br /> <br />By the Rankine analysis for a granular soil <br /> <br />PH ~ KaPv + Pw <br /> <br />= Ka[(Ysat-Y) aJ + Ywa <br /> <br />for Ka <br />Ysat <br />w <br /> <br />= V3 <br />= 120 <br />= 62.4 <br /> <br />PH = ('13 [120-62.4] + 62.4) a <br /> <br />PH=81.6a <br /> <br />Thus, Yeq = 81.6 Ibs/ft03 <br /> <br />For cohesive, nonexpansive clays, the equation becomes <br /> <br />PH = KaPr - V Ka 2c + Pw <br /> <br />PH = [K (Y -Y <br />a sat w <br />PH=81.6a- VKa2c <br /> <br />) + Y ] a - V Ka 2c <br />w <br /> <br />where Ka Rankine active lateral pressure coefficient <br />a Depth from saturated ground surface to point of pressure interest (ft) <br />PH Lateral pressure (pst) <br />Pv ~ Vertical soil pressure (psf) <br />Pw Hydrostatic water pressure (psf) <br />Y' Effective unit weight of soil (pst) <br />Ysat = Unit weight of saturated soil (pef) <br />Yeq Equivalent fluid weight (pef) <br />c Unit cohesion (pst) (Determined by laboratory tests on field samples) <br />Yw Unit weight of water (pef) <br /> <br />Thus for nonexpansive cohesive soils, the net loading is slightly less. It should be pointed <br />out that expansive soils can produce large loads when saturated. However, one should con. <br />suit a soil engineer when dealing with all types of clay <,oils. Table 6.1 gives effective <br />saturated soil weights and equivalent fluid weights for various types of soils which are <br />classified in Table 6.2. Table 6.3 again presents the three conditions assumed for application <br />to basement design. The equivalent fluid weights presented in this chapter will be used in <br />Chapter XI for evaluation of basements in flood plains. <br />