GATE 2018 CE (CE1) – Question 55
A normally consolidated clay sample fails in drained triaxial compression at effective confining pressure 200 kPa and deviator stress 400 kPa. An identical sample is isotropically consolidated to 200 kPa then tested in standard undrained triaxial compression, failing at deviator stress 150 kPa. Developed pore pressure, to one decimal, is ______ kPa.
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Correct answer: 124 to 126
Explanation
For normally consolidated clay with zero effective cohesion, the drained failure principal-stress ratio is $(200+400)/200=3$. For the undrained test, $(350-u)/(200-u)=3$. Solving gives $2u=250$, hence u = 125.0 kPa.