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ENFORCE37555
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Last modified
8/24/2016 7:46:30 PM
Creation date
11/21/2007 3:37:14 PM
Metadata
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Template:
DRMS Permit Index
Permit No
C1981013
IBM Index Class Name
Enforcement
Doc Name
CIVIL ENGINEERING REFERENCE MANUAL
Violation No.
CV2000009
Media Type
D
Archive
No
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III IIIIIIIIIIIIIIII <br />10-14 CIVIL ENGINEERING REFERENCE MANUAL sss <br />T„ is a dimensionless number known as the time Jactor. <br />T„ depends on the degree of consolidation. (!,. U, is the <br />percent of the rota] consolidation (settlement) expected. <br />For U, less than 0.60 (60%•). T„ is given by equation <br />10.44. <br />Tv = 9rU? 10.49 <br />Secondary consolidation can be identiSed by a plot of <br />void ratio (or settlement) versus time on a logazithmic <br />scale. The region of secondary consolidation is chazac- <br />terized by a slope reduction on the plot. The plot. can <br />be used to obtain important parameters necessary to <br />calculate the magnitude and progression of secondary <br />consolidation. <br />Table 10.7 should be used to find T„ Cur larger values of <br />U, . <br />Table 10.7 <br />.Approximate Time Factors <br />U: T <br />V.nJ V.34 <br />0.70 0.90 <br />0.75 0.48 <br />0.80 0.55 <br />o.ss o.70 <br />0.90 0.85 <br />U.95 1.3 <br />1.0 x <br />Following the end of primary consolidation (approxi- <br />mately T„ = 1 in equation 10.44), the rate of consolida- <br />tion will decrease considerably. The continued consoli- <br />dation is known as secondary consolidation. <br />21 SECOI~rDARY CO1~rSOLIDATIOIV <br />Secondary consolidation is a gradual consolidation <br />which continues long after the majorit}' of the initial <br />consolidation has occurred. Secondan• consolidation <br />ma}' not occur at all, as in the case of granular soils. <br />However, secondary consolidation may be a major fac- <br />tor for inorganic clays azld silts. as well as for highly- <br />organic soils. <br />The final void ratio, ef, at the end of the primary con- <br />solidation period is read from the intersection of the <br />projections of the primary and secondary curves. The <br />logarithmic slope of the secondaz}' compression line is <br />known as the secondary compression index, o.'s <br />n = -(logla t2 - loglo tt) 10.45 <br />es - et <br />The coeffltient of secondary compression, Ca, can be <br />derived from this slope. The initial voids ratio, a°, can <br />be estimated from equation 10.39. <br />CQ = a 10.96 <br />l+ea <br />The secondary consolidation during any period t~ - tl <br />is <br />Sseconda:y = CaHlog I t? I 10.9"! <br />tl <br />22 SLOPE STABILITY <br />A. HOMOGENEOUS, SOFT CLAY (~ = 0°) <br />For homogeneous. soft clay, the Taylor chart can be <br />used to determine tkle factor of safety against slope fail- <br />ure.ll .Alternatively. if the factor of safety is itnown. <br />the maximum depth o! cut or the maximum cut angle <br />can be determined. <br />step 1: Calculate the depth factor. d. from the slope <br />height and the depth from the slope toe to <br />the lowest point on the slip circle. <br />d = H 10.98 <br />void ratio, <br />e <br /> <br />tt <br />time, log t <br />Figure 10.12 Primary and Secondar}~ Consolidation <br />The slope height. H. is essentially the depth <br />of the cut. D is the vertical distance from <br />the toe of the slope to the firm base below <br />the clay. <br />step 2: Based on the depth factor; d. and the angle <br />of the slope, determine the stability number, <br />N°. <br />t6 The Secondan' compression index generally ranges from 0 to <br />0.03, and seldom exceeds 0.04. <br />t 7 The nrnJar arc method and mcfhod of adcea can also be used to <br />analyze a parti[ular failure surface. However, if the failure surface <br />is unknown, these methods may require trial and error solutions <br />to lo[ate the critical failure plane. <br />PROFESSIONAL PUBLICATIONS INC. ~ P.O. Boz 199. San Carlos. CA 94070 <br />secondary consolltlarion I `~ <br />
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