22_CEG 4012 Notes Fall 2011 CEG 4012 Notes Fall 2011

# 22_CEG 4012 Notes Fall 2011 CEG 4012 Notes Fall 2011 - If...

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'Imme<llatE! Settlement Case III: p5 ~oaaing-on the-Surface of a Stiff baye Underlain oy a Less Rigl<'FEayer of Great Ihicknes.s Fairly common for upper crust due to desiccation etc. S . .. q H E " III Table P3 gives the C"s values under the center of flexible, circular loads. pe""~~;' o The rland E in the above equation refer to the lower deep layer o If all of the soil is the lower material (I.e. H=O) then in Table P1 C s = 1.0. Table P3 agrees: Cos = 1 for HIS =0 or E,IE, = 1.0. ens < 1 for other HIS and E 1 /E 2 , so e"s is a reduces Pi because of the stiffer upper layer. o C"s reduces settiement considerably: If E , IE, = 100 and HIS = 0.25 (a relatively thin surface layer) then C"s ~ 0.431 and Pi is reduced by 57%.
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Unformatted text preview: If E11E2 = 2 (a relatively small difference in E) and HIS = 0.5 then C"s = 0.747 and Pi is reduced by 25%. o Example: A circular tank of radius 50 ft with a '1Iexible" base is filled with 20 ft of water. The subsurface consists of a 10ft thick stiff clay layer (E = 1x10' psf) underlain by.-<Ldee ., softer c1ay'. . <!.~~sllJE = 5x1 0' psf). What is Pi under the center of theTank? -5. = 1x10' psf = 20 E, 5x1 0' psf HIS ~ 10/100 ~ 0.1 for E,IE, = 10-> C"s = 0.923 ( I . \1:\ c,( > for E,/E, = 100-> C"s = 0.760 5 i~\Cifo\~I( b(J"H~'''' Sy linear interpolation: { 1-05 2 ) and P, =O.905(20')(62.4pcf)(2x50' . , x12"/,= o. ?o" 5x10...
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