Question

In a triaxial test, a soil sample was consolidation under a cell pressure of $700kN/m^2$ and a back pressure of $350kN/m^2$. There after with drainage not allowed, the cell pressure was raised to $800kN/m^2$ resulting in the increased pore water pressure reading of $445kN/m^2$. The axial load was then increased to give a deviator stress of $575kN/m^2$(while the cell pressure remained at $800kN/m^2$) and a pore pressure reading of $640kN/m^2$. The pore pressure coefficients A and B are respectively?

• A. 0.95,0.36
• B. 0.45,0.75
• C. 0.75,0.45
• D. 0.36,0.95

Answer 1

The correct option is D 0.36,0.95

$B=\frac{\Delta u_1}{\Delta {\sigma }_3}$

$=\frac{445-350}{800-700}=\frac{95}{100}=0.95$

$\overline{A}=\frac{\Delta u_2}{\Delta {\sigma }_1-\Delta {\sigma }_3}=\frac{640-445}{575}=\frac{195}{575}=0.339$

$\overline{A}=A.B$

$A=\frac{0.339}{0.95}=0.357\underset{–}{\sim }0.36$