Analytical Chem Soil HW Solutions 53

Analytical Chem Soil HW Solutions 53 - v , and the vertical...

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53 Even for small changes in stress, the soil stiffness is clearly dependent on the initial stress state, whether the sample is being loaded or unloaded and whether the soil is normally or over consolidated. In determining an appropriate stiffness for use in a design calculation, it is necessary to replicate the stress history, stress state and anticipated stress path of the soil in the field. Analysis of data from the consolidation phase Q4.4 Data from one stage of an oedometer test are given below. Time, min 0.25 1 4 9 16 25 Settlemen t mm 0.063 0.075 0.103 0.133 0.160 0.185 Time, min 36 49 64 81 100 196 Settlemen t mm 0.210 0.228 0.240 0.250 0.258 0.265 Load increment: 25 - 50 kPa Sample diameter: 76 mm Initial sample thickness: 20 mm Two-way drainage For this load increment, estimate the one-dimensional modulus E' o , the consolidation coefficient c
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Unformatted text preview: v , and the vertical permeability of the soil k v . (It may be assumed that the initial slope of a graph of proportional settlement R= ρ / ρ ult against the square root of the time factor T=c v t/d 2 is equal to √ (4/3), ie R = √ (4T/3).) What factors would you take into account in the laboratory determination of E' o c v and k v for use in design? What difficulties might you encounter in attempting to use oedometer test results to predict rates of settlement in the field? [University of London 2nd year BEng (Civil Engineering) examination, Queen Mary and Westfield College (part question)] Q4.4 Solution Plot a graph of settlement against √ time (Figure Q4.4): time t, min 0.25 1 4 9 16 25 36 49 64 81 100 196 settlement ρ , mm .063 .075 .103 .133 .160 .185 .210 .228 .240 .250 .258 .265 t, min 0.5 0.5 1 2 3 4 5 6 7 8 9 10 14...
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This note was uploaded on 12/28/2011 for the course CHM 4302 taught by Professor Stuartchalk during the Fall '11 term at UNF.

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