Analytical Chem Soil HW Solutions 18

Analytical Chem Soil HW Solutions 18 - Vertical load V, N...

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Unformatted text preview: Vertical load V, N 100 200 300 normal effective stress σ', kPa 27.8 55.6 83.3 ln(σ') 3.325 4.018 4.422 Shear Shear load stress τult, Fult, N kPa 53 14.7 105 29.2 156 43.3 Water content w, % Specific volume v 35.1 31.3 29.5 1.95 1.85 1.80 Plot graphs of τult against σ' and v against lnσ' to determine the critical state parameters, as in main text Figure 2.28 (Example 2.2). φ'crit ≈ 28°; vo ≈ 2.43; λ ≈ 0.14 During the undrained tests, there is no overall volume change. Assuming that the specific volume is uniform throughout the sample, it must remain constant during the test. The critical state eventually reached therefore depends on the as-tested specific volume. Our model predicts that, at the critical state, the vertical effective stress σ' is related to the specific volume by the expression v = vo - λ.lnσ' (main text Equation 2.11) or σ' = exp{(vo-v)/λ} The normal effective stress at the critical state is related to the shear stress τult by the expression τult = σ'.tanφ'crit (main text Equation 2.10) Hence τult = exp{(vo-v)/λ}.tanφ'crit where v = 1 + w.Gs. The calculated and measured values of τult for the undrained tests are compared below: Vertical load V, N normal effective stress σ', kPa Shear load Fult, N 100 200 300 27.8 55.6 83.3 42 80 120 Measured shear stress τult, kPa 11.7 22.2 33.3 Water content w, % Specific volume v 36.0 32.6 20.6 1.972 1.880 1.826 Calculated shear stress, τult kPa 14.0 27.0 39.8 The measured values are smaller than the theoretical values by about 16%. This is probably due to internal drainage and discontinuous sample behaviour. 18 ...
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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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