ABSTRACT: Chimneying disintegration, one of several shallow stope failure mechanisms of hard rock mines, develops rapidly to surface in weak rock masses from depths as much as 275 m. A limit equilibrium equation is presented, which is based on the inability of the rock mass to support its own weight and fails by shearing along lines of active pressure. The material's ability to breakdown to small sizes allows an effective shear rupture to develop. Four cases have been studied to apply and evaluate the analytical equation, numerical modelling and a dedicated shallow stope empirical method. The equation has returned factors of safety representative of the failed and unfailed cases. A numerical correlation between critical span and rock mass cohesion is presented, and the span and material strength limits are discussed for chimneying disintegration to occur. Numerical modelling can represent weak rock mass behaviour and indicate where failures start but not the outline or continuity of failure to surface. The dedicated empirical method has limitations in predicting the peripheral location and stope depth from which failure can occur.

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