43_CEG 4012 Notes Fall 2011 CEG 4012 Notes Fall 2011

43_CEG 4012 Notes Fall 2011 CEG 4012 Notes Fall 2011 - a...

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p26 pc = total settlement p "- = immediate settlement ~ = (primary) consolidation settlement = secondary compression (creep) Secondary Compression: P = Pi+ Pc . . Ps where: p Pi p, p, o Secondary compression is the portion of time·dependent settlement that occurs at essentially constant effective stress. a The rate of seconda compression is not 13 enden on the flow of water is not de endent o,n cay layer thickness, and i. relallveJY.J:J:!Q.S--lantJor normal engineering stress increases. a Secondary compression occurs slowly with a continually decreasing rate. a Tbe secondary COffilllil-ssioo portion.oLtbe. .c.onsolldatioo cu[\(e is approximately linear on aiL!iJolj-limEl-f3le . .... a Secondary compression usually estimated from a lab consolidation test. a The exact cause of secondary compression is unknown, but is possibly a readjustment of th.e double water layer surrounding the clay particles. a
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Unformatted text preview: a The ratio of secondary to primary consolidation increases as () ({j.) the ratio of stress increment to initial stress decreases: PPc S i as a~ov J. i.e. watch out for small stress increases in thick clay layers. nd of olidation Secondary Compression Index (fit "straight" line after epl C. = ·M /lIlog t = -(13,-13,) flog (t,/ t,) = typically 3-4% of C c , , , ep= void ratio at e-··--····--r-------lie . ...Ps l" , , primary cons , , , , , , ep Void Ratio, 13 (from dial readings) log time, t tp t, o As before: {j.H = -(j.e(. ...'::I. ... ) = Ps 1 + eo and = ( C.H ) 10 (.!r.) Ps 1 + 13 g t o p where: tF = time at which magnitude of secondary compression required tp = time corresponding to end of primary consolidation o Note: C'.= [CaI(l +epl] found by Mesri to have correlation with water content, can replace CJ(l +130) with C'. in above equation for ps (see Das Fig. 8.19)...
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This note was uploaded on 02/10/2012 for the course CEG 4012 taught by Professor Staff during the Fall '08 term at University of Florida.

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