Failure criteria (Mohr-Coulomb)
Input(s)
\(\sigma_{a}\): Principle Stress (psi)
\(\sigma_{b}\): Second Strongest Stress (psi)
B: Angle Between Fault and Direction of Principle Stress (degrees)
Output(s)
\(\tau\): Shear Stress (psi)
\(\sigma\): Normal Stress (psi)
Formula(s)
\[
\begin{gathered}
\tau=0.5 *\left(\sigma_{\mathrm{a}}-\sigma_{\mathrm{b}}\right) * \sin (2 * \beta) \\
\sigma=0.5 *\left(\sigma_{\mathrm{a}}+\sigma_{\mathrm{b}}\right)+0.5 *\left(\sigma_{\mathrm{a}}-\sigma_{\mathrm{b}}\right) * \cos (2 * \beta)
\end{gathered}
\]
Reference(s)
Mark D. Zoback, Reservoir Geomechanics, Cambridge University Press, UK, Page: 89.