Safety Pre-Control of Stope Roof Fall Accidents Using Combined Event Tree and Fuzzy Numbers in China’s Underground Noncoal Mines

Among the accidents in China's underground noncoal mines including ferrous metal mines, nonferrous metal mines and nonmetallic mines, roof fall accidents are always extremely bad. The application of risk assessment to avoid roof fall accidents in coal mines is widespread. However, the traditional method has defects in its accuracy, cost, and simplicity. It cannot fundamentally ensure that workers survive a roof fall accident. Therefore, there is no great referential significance for noncoal mines. In this paper, supposing that roof fall accidents in underground noncoal mines are inevitable, we assess where we should start to take measures to prevent worker deaths. On the basis of a detailed investigation, units including those working far from the roof, noticing the signs, etc. were identified, and then a concise event tree model was built. Under this framework, the event tree model has 2 consequences, including being alive and death, and 13 scenarios related to accident occurrence. In this research, the probability of unit events was evaluated by using triangular fuzzy numbers. In addition, we found 3 scenarios with death, and then we calculated their respective probabilities. Finally, regarding the death scenario with the highest risk value, the paper recommends that priority measures should be taken to prevent deaths in roof fall accidents. The method in this paper provides a theoretical basis for pre-control measures and it is efficient, inexpensive, and simplified. Even if a roof fall accident is inevitable, we know where to start to take pre-control measures to prevent worker deaths.