Question

In an unconsolidated undrained triaxial test, it is observed that an increase is cell pressure from 150 kPa to 250 kPa leads to a pore pressure increase of 80 kPa. It is further observed that, an increase of 50 kPa in deviatoric stress results in an increase of 25 kPa in the pore pressure. The value of Skempton's pore pressure parameter B is:

• A. 0.5
• B. 0.625
• C. 0.8
• D. 1.0

Answer 1

The correct option is C 0.8

$\Delta U=B[\Delta {\sigma }_3+A(\Delta {\sigma }_1-\Delta {\sigma }_3\left)\right]$

During cell pressure application, ${\sigma }_1={\sigma }_3$

Hence, $\Delta {\sigma }_1=\Delta {\sigma }_3$

$\Delta U=B\Delta {\sigma }_3$

$80=B\left(100\right)$

B = 0.8