Question

In a triaxial compression test, the major principal stress was $90kPa$ and the minor principal stress was $30kPa$, at failure. The pore pressure at failure was observed to be $10kPa$. The tangent of the angle of shearing resistance of the sandy soil that was tested was

• A. $1/2$
• B. $1/3$
• C. $2/3$
• D. $3/4$

Answer 1

The correct option is D $3/4$

$sin\varphi =\frac{{\overline{\sigma }}_1-{\overline{\sigma }}_3}{{\overline{\sigma }}_1+{\overline{\sigma }}_3}$

$=\frac{(90-10)-(30-10)}{(90-10)+(30-10)}=\frac{60}{100}$

$sin\varphi =\frac{3}{5}$
$\therefore tan\varphi =\frac{3}{4}$