Analytical Chem Soil HW Solutions 15

Analytical Chem Soil HW Solutions 15 - Consideration of...

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15 QUESTIONS AND SOLUTIONS: CHAPTER 2 The shearbox test Q2.1 Describe with the aid of a diagram the essential features of the conventional shearbox apparatus. Stating clearly the assumptions you need to make, show how the quantities measured during the test are related to the stresses and strains in the soil sample. [University of London 2nd year BEng (Civil Engineering) examination, King's College (part question)] Q2.1 Solution Diagram of shear box: See main text Figure 2.14 Assume that the stresses and strains are uniform and continuous, and that the actual deformation in shear (main text Figure 2.15a) is idealised as indicated in main text Figure 2.15b. The known or measured quantities are A the sample area on plan, assumed to remain constant during the test) H the initial height of the sample N the normal (hanger) load F the shear force x the relative horizontal displacement between the upper and lower halves of the shearbox y the upward movement of the shearbox lid.
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Unformatted text preview: Consideration of main text Figure 2.15b gives strains shear strain γ = x/H volumetric strain ε vol = -y/H In terms of stresses, shear stress on central horizontal plane τ = F/A normal stress on central horizontal plane σ = N/A If it is further assumed that the pore water pressure u is zero (so that ' = ) and the central horizontal plane is the plane of maximum stress obliquity ( / ') max , a Mohr circle of stress may be drawn (eg main text Figure 2.30), and the mobilised effective angle of friction is φ ' mob = tan-1 {( / ') max } Q2.2 With the aid of sketches, describe, explain and contrast the results you would expect to obtain from conventional shearbox tests on samples of dry sand which were (a) initially loose, and (b) initially dense. What factors would you take into account in selecting a soil strength parameter for use in design? [University of London 2nd year BEng (Civil Engineering) examination, King's College (part question)]...
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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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