For normally consolidated clay in a drained Triaxial Test, c’ = 0
\({{\sigma }_{1}}'=~{{\sigma }_{3}}'{{\left( \text{tan }\!\!~\!\!\text{ }\left[ 45+\frac{\varnothing '}{2} \right] \right)}^{2}}\)
\(\sigma _{3}^{'}+{{\sigma }_{d}}'=~{{\sigma }_{3}}'{{\left( \text{tan }\!\!~\!\!\text{ }\left[ 45+\frac{\varnothing '}{2} \right] \right)}^{2}}~\)…….. u = 0
In the drained test:
\(200+400=~200{{\left( \text{tan }\!\!~\!\!\text{ }\left[ 45+\frac{\varnothing '}{2} \right] \right)}^{2}}\)
ϕ' = 30⁰
For standard undrained Triaxial test,
\({{\sigma }_{1}}'=~{{\sigma }_{3}}'{{\left( \text{tan }\!\!~\!\!\text{ }\left[ 45+\frac{\varnothing '}{2} \right] \right)}^{2}}\) ……. In terms of effective stress.
\(({{\text{ }\!\!\sigma\!\!\text{ }}_{1}}-\text{u})=\text{ }\!\!~\!\!\text{ }({{\text{ }\!\!\sigma\!\!\text{ }}_{3}}-\text{u}){{\left( \text{tan }\!\!~\!\!\text{ }\left[ 45+\frac{\varnothing \text{ }\!\!'\!\!\text{ }}{2} \right] \right)}^{2}}\)
\(({{\text{ }\!\!\sigma\!\!\text{ }}_{3}}+{{\text{ }\!\!\sigma\!\!\text{ }}_{\text{d}}}-\text{u})=\text{ }\!\!~\!\!\text{ }({{\text{ }\!\!\sigma\!\!\text{ }}_{3}}-\text{u}){{\left( \text{tan }\!\!~\!\!\text{ }\left[ 45+\frac{\varnothing \text{ }\!\!'\!\!\text{ }}{2} \right] \right)}^{2}}\)
\(\left( 200+150-\text{u} \right)=\left( 200-\text{u} \right){{\left( \text{tan }\!\!~\!\!\text{ }\left[ 45+\frac{\varnothing \text{ }\!\!'\!\!\text{ }}{2} \right] \right)}^{2}}\)
∴ u = 125 KPa