\[\sigma_{1}=\sigma_{3}+\sigma_{d}\]
\[\sigma_{d (failure)}=\left(\sigma_{1}+\sigma_{3}\right)_{\text {failure}} \frac{P}{A}\]
\[\tau_{S}=C+\overline{\sigma_{n}} \tan \phi\]
\[\text {A}=\frac{A_{0}\left(1 \pm \epsilon_{v}\right)}{\left(1-\epsilon_{L}\right)}\]
\[\text {A}=\frac{A_{0}\left(1 \pm \epsilon_{v}\right)}{\left(1-\epsilon_{L}\right)}\]
\[\varepsilon_{v}=\frac{\Delta V}{V}\]