Modeling the progressive failure of hard rock pillars

An enhanced cohesion weakening and friction strengthening model is proposed to simulate the progressive failure of hard rock pillars using two- and three-dimensional finite difference analysis. The documented behavior of 85 pillars in two mines was used for model validation. The numerical models successfully separated unstable/failed pillars from stable pillars and also captured the observed mechanism of progressive failure in hard rock pillars. Pillar stress-strain curves indicated that while pillars with W/H < 2 exhibit strain softening, wider pillars begin to display strain hardening. It was shown that strength of wide pillars may be overestimated by conventional models using empirically estimated parameters.