Analytical Chem Soil HW Solutions 62

Analytical Chem Soil HW Solutions 62 - hence s' = σc + q/2...

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Unformatted text preview: hence s' = σc + q/2 - u and φ'mob = sin-1{q/(2σc + q - 2u) Also, the change in pore water pressure Δu = u - uo, where uo is the pore water pressure at the start of shear (= 274.6kPa in this case). Hence Axial strain εa, % 0 0.05 Shear strain γ = 1.5×εa, % Deviator stress q, kPa Pore water pressure u, kPa Δu = u - uo, kPa 0 0.075 0.135 φ'mob = 0.09 0.18 0.39 0.69 1.51 0.27 0.585 1.035 2.265 0 10.9 22.3 274.6 280.3 284.6 0 5.7 10.0 33.5 290.8 16.2 45.0 300.0 25.4 53.5 307.6 33.0 65.4 314.4 39.8 0 2.4 7.6 10.6 13.0 16.0 p = σc + q/3, kPa 400 403.6 407.4 411.2 415.0 417.8 421.8 p' = σc + q/3 - u, kPa 125.4 123.3 122.8 120.4 115.0 110.2 107.4 Axial strain εa, % 3.22 4.74 6.13 7.89 9.39 11.03 Shear strain γ = 1.5×εa, % Deviator stress q, kPa Pore water pressure u, kPa Δu = u - uo, kPa 4.83 7.11 9.20 11.84 14.1 16.5 79.0 85.7 317.0 315.1 42.4 40.5 89.6 91.4 312.6 312.1 38.0 37.5 93.9 312.7 38.1 94.0 312.8 38.2 φ'mob = 18.8 19.8 20.5 20.5 5.1 sin-1{q/(2σc + q - 2u), ° 19.6 20.0 sin-1{q/(2σc + q - 2u), ° p = σc + q/3, kPa 426.3 428.6 429.9 430.5 431.3 431.3 p' = σc + q/3 - u, kPa 109.3 113.5 117.3 118.4 118.6 118.5 (Calculated values are shown in bold type) Graphs of mobilized strength φ'mob and pore water change Δu against shear strain γ, and the total and effective stress paths in the q,p and q,p' planes, are plotted in Figures Q5.1a and b. There is no peak strength, and the sample has positive pore water pressures at failure. The sample is therefore probably wet of critical, i.e. lightly overconsolidated. The effective stress path appears to follow an undrained state boundary, but near the end veers off to the right (i.e. the pore water pressures start to reduce) to reach the critical state line at a higher value of q (and p') than might otherwise have been expected. The reason for this is unclear, but possible causes include the development of a rupture and/or sample anisotropy. 62 ...
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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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