Challenges of a coupled combined finite-discrete element approach to explosive induced rock fragmentation

Abstract

Rock blasting involves rock and explosive charge. As the explosive charge is initiated in the confined space of the borehole, the explosive is turned into hot detonation gases that press on borehole walls initiating cracks in the rock. Expansion of this detonation gas and its penetration into the cracks and joints accompanied by escape of the detonation gas results in both dissipation of the gas energy and energy transfer from the gas onto the fracturing rock and subsequent acceleration of the rock mass. The result of this coupled expansion of detonation gas and stressing of the rock mass, is a rapid pressure drop in the gas accompanied by fracture of the rock mass followed by fragmentation. Motion of the rock fragments, when coupled with energy dissipation mechanisms, gravity and boundary constraints, leads to the formation of a pile of blasted rock. Although the combined finite-discrete element analysis of rock blasting includes a whole range of algorithms such as algorithms for interaction between fragments, motion of rock fragments, expansion of detonation gas, etc., fracture and fragmentation together with the gas model have been in the focus of the recent research efforts and the main thrust of this paper is to summarise the latest developments. This paper discusses the algorithmic aspects of the proposed approaches together with the problems associated with the combined finite-discrete element analysis of rock blasting operation as a whole.