Analytical Chem Soil HW Solutions 19

Analytical Chem Soil HW Solutions 19 - Q2.4 Solution (a)...

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19 Determination of peak strengths Q2.4 The following results were obtained from a shearbox test on a 60 mm × 60 mm sample of dry sand of unit weight 18 kN/m 3 . Reading on proving ring deflexion dial gauge (divisions) Zero force 91 Peak shear force for a hanger load of 3kg 128 Peak shear force for a hanger load of 10kg 162 Peak shear force for a hanger load of 20kg 210 One division on the proving ring dial gauge corresponds to a force of 1.1N across the proving ring. (a) Plot the data on a graph of shear stress against normal effective stress, and sketch the peak strength failure envelope. (b) What is the peak resistance to shear on a horizontal plane at a depth of 3 m below the top of a dry embankment made from this soil? (c) A model of the embankment is constructed from the same sand at a scale of 1:10. What is the peak resistance to shear on a horizontal plane at a depth of 300mm below the top of the model? (d) Would you expect the model to behave in the same way as the real embankment?
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Unformatted text preview: Q2.4 Solution (a) The normal stress on the sample is given by the hanger load (kg) 9.81 (N/kg) the sample area, 0.06m 0.06m = 3.6 10-3 m 2 , 1000 to convert from Pa to kPa. The shear force on the sample is given by 1.1 (the number of proving ring dial divisions - the number of divisions at zero load), i.e. 1.1 (n - 91). To convert this to the shear stress, it is necessary to divide the shear force by the area of the sample, 0.06m 0.06m = 3.6 10-3 m 2 , and divide by 1000 to convert from Pa to kPa. Hanger load, kg Normal stress, kPa Peak shear load, N Peak shear stress, kPa 3 8.175 40.7 11.31 10 27.25 78.1 21.69 20 54.5 130.9 36.36 These data are plotted on a graph of against ' in Figure Q2.4. The peak strength failure envelope is highly non-linear, with ' peak = 55 at ' 8 kPa, falling to ' peak = 34 at ' 55 kPa...
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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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