After a large-scale failure, the rock mass usually doesn’t stabilize immediately but exhibits post-failure behaviour that can continue for a long time. An understanding of potential post-failure residual rock mass behaviour is critical when making decisions on re-entry time, continuation of mining activities and also potential utilisation of the effected areas. In many cases of large-scale geotechnical events e.g. mine disasters, rescue teams must enter affected areas. In such cases, there is need to determine minimum re-entry time so that the teams are not exposed to hazards of further ground deterioration. Post-failure behaviour also must be considered when further mining activities are planned near damaged ground. Knowledge of long-term post-failure behaviour is critical for determining the long-term surface stability over closed underground mines.
Mining geometry such as pillar width: height ratio and extraction ratio determine the post-failure behaviour. With increasing pillar width: height ratio, post-failure behaviour changes from brittle to ductile. For slender pillars the post-failure behaviour is brittle; for squat pillars it is typically ductile.