Strain-based failure criteria for rocks: State of the art and recent advances

The paper offers a critical overview of the current state of the art and the most recent research in the field of strain-based failure criteria for rocks. Particular attention is paid to the critical tensile strain criterion according to which failure occurs when the minimum principal strain reaches a limiting value. This criterion seems to hold true for low confinement conditions. Results of recent experimental studies show, however, that the least principal strain (the greatest extensional strain) at strength failure is not, in general, constant under triaxial compression conditions but that it assumes different values depending on the magnitude of confining pressure in conventional triaxial compression tests or the intermediate and minimum principal stresses in true triaxial compression tests. Based on these study results, a new failure criterion has been proposed according to which the octahedral shear strain at strength failure is a linearly increasing function of the maximum principal strain. This criterion is of a more general character than those known to date and is applicable to both axisymmetric and asymmetric triaxial stress conditions.