changes.mady.by.user Arthur Aslanyan (Nafta College)
Saved on Nov 22, 2018
...
\displaystyle c_r (\phi, p) = c_{ri} \cdot \frac{ \ln \left( \frac{ p_n }{p_{\rm max}} \right) }{ \ln \left( \frac{p_{ni}}{p_{\rm max}} \right) }
p_n = p_{\rm min} + 1.75 \cdot \phi^{0.51} \cdot (p_{\rm max} - p)
p_{ni} = p_{\rm min} + 1.75 \cdot \phi^{0.51} \cdot (p_{\rm max} - p_i)
where
Sandstone
p_{\rm min} = 151 \, {\rm psi}, \quad p_{\rm max} = 30,000 \, {\rm psi}