Maximum principal stress failure (Hoek and Brown)

Input(s)

$\sigma_{b}$: Second Largest Stress (psi)

C: Rock Compressive Strength (lbf)

m: Hoek - Brown Constant Dependent on Rock Type (dimensionless)

s: Hoek and Brown Constant Dependent on Shape (dimensionless)

Output(s)

$\sigma_{a}$: Principal Stress (psi)

Formula(s)

$$ \sigma_{\mathrm{a}}=\sigma_{\mathrm{b}}+\left(\mathrm{C} *\left(\mathrm{~m}_{*} *\left(\frac{\sigma_{\mathrm{b}}}{\mathrm{C}}\right)+\mathrm{s}\right)^{0.5}\right) $$

Reference(s)

Mark D. Zoback, Reservoir Geomechanics, Cambridge University Press, UK, Page: 98.