Abstract

Coarse arches are a common issue in caving mines where large fragments are expected. These arches interrupt ore flow in drawpoints, decreasing available draw area, and also increasing the possibility of non-uniform draw, which can increase fine migration, mud-rush risk, and induced stress in the caved column. Moreover, hang-up removal is operationally complex and dangerous. The literature on gravity flow indicates that coarse arches are mainly influenced by the ratio between the rock fragments and the size of the opening and stresses, but some key variables have not been quantified. Here, the influence of fragment-size distribution and drawbell geometry on hang-up formation is analyzed through controlled laboratory experiments in a physical model. Results show that drawbell parameters, such as length, width and angle are relevant parameters in hang-up events. In particular, the ratiosD(L)/d(80)andD(W)/d(80)as well asV(DB)/V(p)are key to hang-up events, the probability of which will decrease when these ratios increase.