Mohr-Coulomb

The most common way to model soil shear strength is with the Mohr-Coulomb equation:

 

 

where:

s = shear strength

c’ = effective cohesion

 

= total normal stress

 

u = pore pressure

 

= effective angle of internal friction (phi)

 

The Mohr-Coulomb equation can be used for either total or effective stress conditions. For a total stress analysis, cohesion and friction angle are defined for total stress conditions. Pore water pressure is not considered, and the Mohr-Coulomb equation is simply: