**Shear Plane Determination in Mohr Coulombs Model
**

**A. I. Ivanov
**

*Institute of Environmental Geoscience, Russian Academy of Sciences,Ulanskii per. 13, Moscow, 101000 Russia
*

Received May 14, 1998

**Abstract**—The classical formulation of Mohr–Coulomb’s law of shear strength gives no indications as to fail-

ure plane orientation. In practice, the orientation of this plane is determined from various external indications,

i.e., through conjecture. This paper suggests a tensor-based generalized formulation of Mohr–Coulomb’s law.

Based on this formulation, failure plane orientation is defined as the direction, along which a certain quadratic–

bilinear form of the stress tensor, related to Mohr–Coulomb’s law, attains an extremum.