Assessment of effects of geological and geotechnical factors on coal burst proneness

A rockburst is an energy release phenomenon which occurs by the interaction of multiple factors in complex geological and geotechnical conditions. Rockbursts have been recognised as one of the most catastrophic hazards experienced in underground mines and tunnels. In coal mining terminology, coal burst refers specifically to a burst event that expels coal into a mine opening. Despite the widespread and long-lasting experience of bursts, their underlying mechanisms are still not fully understood. The ultimate aim of this thesis was to improve the understanding of the fundamental coal burst mechanisms and assist mine operators to evaluate coal burst proneness in their mines. Firstly, a semi-quantitative classification system has been proposed in this study to assess coal burst proneness in underground coal mines. Moreover, an energy-based quantitative burst proneness rating system specifically designed for development roadways has also been introduced. Several burst and no-burst cases from Australia, China and the United Sates were back-analysed using the developed systems. Furthermore, numerical analyses have been conducted to examine the effects of geological structures on burst proneness near roadways. The model outcomes were then compared to benchmark cases to assess relative proneness of varying mining environments. The studies quantified the impacts of geological faults and dykes on energy release and storage mechanisms; and showed that unfavourably positioned geological structures can increase coal burst proneness in roadways. In addition, the effects of pre-existing discontinuities on coal mass strength and energy release characteristics have been investigated. It was found that higher cleat density can notably reduce energy release magnitudes and rates in a coal mass. To sum up, along with several other factors, mining depth, geological structures and coal mass conditions have been shown to play an important role in elevation of risk of coal burst occurrence. The outcomes of this thesis have demonstrated the complexity of coal bursts and highlighted the importance of a multifactorial approach in evaluating of coal burst risks in mines. The results of the parametric analyses and proposed risk-based methodologies provide an improved understanding of coal burst mechanisms and guidance for effective management of coal burst risk in underground coal mines