Unformatted text preview: 72 starts to deform plastically. As it cannot compress (due to the constraint of the undrained test), excess pore water pressures are generated. The rate of increase in pore water pressure with deviator stress, du/dq, increases suddenly at Y. The critical state corresponding to the specific volume of the sample as tested is reached (presumably) as C. At the critical state, deformatiuon could continue at constant q, p' and v (although we do not have the evidence for this in the data we are given). The total stress path has slope dq/dp = 3, because p = 1 / 3 (q + CP) and CP = constant. Assuming that the sample deforms as a continuum, so that internal stresses/strains may be deduced from boundary measurements; that C is the critical state; and that the line joining critical states (the CSL) goes through the origin, Μ = q c /p' c = 63/61.7 ⇒ Μ = 1.02 A drained test starting from a cell pressure of 100 kPa has u = 0 and p' = 100 + q/3 kPa. It will reach the CSL when q = Μ .p' and p' = 100 + q/3, or with ....
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- Fall '11
- Analytical Chemistry, kPa, Pore water pressure, pore water, cell pressure