Consolidated undrained vs unconsolidated undrained test

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Homework Statement


In the consolidated undrained , why there's only increase in pore water pressure due to deviator stress application ? Why in unconsolidated undrained test , why there is both increase in pore water pressure due to deviator stress application (ud) and also uc ?

Homework Equations

The Attempt at a Solution


IMO , in the consolidated undrained , the total pore pressure should be sum of ud and uc ...
 
Attachments
  • Printed textbook page, section 12.10 Consolidated-Undrained Triaxial Test, describing the saturated specimen consolidated under chamber pressure with drainage open, then sheared with the drainage line closed.
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  • Figure 12.28 with seven panels: specimen diagrams, volume change against time, deviator stress and pore water pressure against axial strain for loose and dense sand and clay, and the pore pressure parameter formula A = Δu_d / Δσ_d.
    647.png
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  • Textbook page section 12.11 on the unconsolidated-undrained triaxial test with Equation 12.31, u = uc + Δud, highlighted by a red box around uc, and Equation 12.32, u = Bσ3 + ĀΔσd = Bσ3 + Ā(σ1 − σ3).
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Discussion

Not my field but...

Initially I shared your confusion. The only thing I can see is that in 12:10 there are two phases described. Drainage is allowed in the first phase which is when external chamber pressure is applied. If the chamber is open to allow drainage then pressure inside doesn't/can't build up.

In 2:11 the chamber is sealed when external pressure is applied so the pressure inside can increase.

I might be wrong but that's the only way I could make sense of it.
 

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