Research on risk analysis and precautionary measures of coal-and-gas outbursts in hydraulic tunnels

In order to explore the risk of coal-and-gas outbursts in hydraulic tunnels and their prevention and control measures, the No. 6 Middle Coal Seam, at the inlet section heading face of Shuidaqiao Tunnel in Guizhou Province, China, was taken as the research background. Using the testing data, the No. 6 Middle Coal Seam was determined to have a high risk of coal-and-gas outburst by both the single-index analysis method and the comprehensive D and K index analysis method. An integrated outburst precautionary measure of “advanced geological prediction + grouting cut-off wall + gas pre-drainage + grouting sealing + effectiveness verification” in a segmented and multi-cycle manner was designed and implemented. The on-site gas inspection results show that no further occurrences of gas over-limit or outburst phenomena have been observed, indicating that the above coal-and-gas outburst precautionary measure is scientific and effective. The research results can provide references for risk analysis of coal-and-gas outburst and its prevention and control in similar hydraulic tunnels passing through coal seams.