Surface goaf gas drainage strategies for highly gassy longwall mines

摘要

Mine gas control is a major issue in most of the gassy underground coal mines due to its direct impact on safety, production-delays and cost of production. Analysis of the gas data from different collieries in Australia showed that longwall gas emissions have increased substantially over the years. Simply drilling a surface goaf hole into the long-wall goaf or increasing the number of goaf holes in the palieI or decreasing goaf hole spacing does not seem to be effective in controlling high goaf gas emissions. A major research project has been undertaken by CSIRO in collaboration with mine sites to address this goaf gas control issue with the aim of developing effective and optimum goaf gas drainage strategies. The project has combined extensive field studies with computational fluid dynamics (CFD) models to characterise goaf gas flow patterns and develop effective gas control strategies. The research work specifically involved review of gas control issues at field sites, goaf gas monitoring, tracer gas tests, CFD simulations and extensive field trials. Field demonstration studies of the new optimum strategies have been conducted at one of the collieries in Australia. The project results have shown that the optimum strategies were highly successful in improving the overall efficiency of goaf gas drainage systems at the field site. Results of the goaf gas flow characterisation studies and field demonstration studies are summarised in this paper.