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31 <br /> � v — <br /> DDC improved soil or native soil excavated to at least 8-ft depth and <br /> replaced with compacted fill: <br /> qa = 430B + 960D <br /> If the soils to a depth of 2 ft below the ringwall are improved or compacted <br /> to 95 percent of the maximum dry density (determined by ASTM D 1557) , the follow- <br /> ing equation is applicable: <br /> q = 580B + 1150D <br /> a <br /> in which: q = allowable bearing pressure (psf) <br /> gmax = maximum allowable bearing pressure (psf) <br /> a <br /> B & D = footing or pad width and depth (ft) <br /> These equations are for vertical loads applied at the center of the ringwall <br /> and include a factor of safety in excess of 2.5. A 33 percent increase in <br /> allowable bearing pressure can be used for seismic design. <br /> If compacted structural fill is reinforced with geotextiles in accordance <br /> with previous discussions, the allowable bearing pressure can be increased. <br /> Provided the reinforcing extends down from the base of the ringwall to a depth of <br /> at least 2 ft, the allowable bearing pressures for seismic loads can be increased <br /> by 500 psf. <br /> Sliding. Sliding resistance can be computed based on the values of passive <br /> pressure and base friction provided in the discussion for the turbine and boiler <br /> foundations. <br /> Settlement. Estimated settlements for various combinations of footing <br /> sizes, applied net pressure, and subsurface conditions are provided on Plate 44. <br /> Note these values are approximate and are additive to values of settlement due to <br /> the planned grade raise at the site. Settlement considerations were discussed <br /> more completely in the previous Foundation Considerations of this report. <br /> 1144A/CC-31 FOA McClelland <br />