Effective stress
= Effective stress
{title2=$\boldsymbol\sigma'$}
The load carried by the solid skeleton or contacts after allowing for <pore fluid pressure>. In compression-positive form an elementary law is $\boldsymbol\sigma'=\boldsymbol\sigma^c-\alpha P\mathbf I$; the contact approximation often takes $\alpha=1$. Fixed-total-stress pressure changes translate a <Mohr circle> without changing its radius.