Designing an Effective EDZ Cutoff in High Stress Environments

Abstract

Practical experience indicates that the initiation of stress-induced damage occurs when the damage index (Di) expressed as ratio of the maximum tangential boundary stress to the unconfined compressive strength of the rock mass exceeds 0.4. For the Mine-by test tunnel the extent of this damaged zone can be approximated by a constant deviatoric stress criterion, (al - a3 = 70 MPa). Numerical analyses, using the constant deviatoric stress criterion, and observations, indicate that a torus-shaped seal is effective in providing a cut-off to the continuous zone of stress-induced damage that formed around the Mine-by test tunnel.