Question

In a triaxial test at failure, major principal stress was 180 kPa, minor principal stress was 100 kPa, and pore pressure was 20 kPa. The tangent of the angle of shearing resistance of the sandy soil tested is

• A. $1/3$
• B. $2/7$
• C. $1/2$
• D. $1/6$

Answer 1

The correct option is A $1/3$

Major principal stress:
${\overline{\sigma }}_1={\sigma }_1-u=180-20=160kPa$
Minor principal stress:
${\overline{\sigma }}_3={\sigma }_3-u=100-20=80kPa$
For sand,
$c=0$
${\sigma }_1={\sigma }_{3}ta{n}^2({45}^o+\frac{\varphi }{2})$
$Thusonsolving\varphi ={19.47}^o$
$Andtan\varphi =0.353$
So, nearest option is (a)