Research on outburst elimination technology of shield tunneling in middle roadway of outburst thin coal seam

In order to solve the problem of difficult prevention and control of coal and gas outburst in thin coal seam, the distribution characteristics of effective extraction area in thin coal seam are analyzed. Due to the limitation of the thickness of the thin coal seam, the expansion of the effective gas extraction area in the vertical direction is hindered, and it tends to extend in the horizontal direction, resulting in the effective extraction radius in the horizontal direction is much larger than the thickness of the coal seam. The effective extraction area is elliptically distributed. The gas seepage field mainly focuses on the direction and inclination of the coal seam. According to the characteristics, it is pointed out that the outburst elimination technology of shield tunneling in middle roadway based on the coal seam extraction mode can make the extraction area connected together. The technology is more suitable for gas extraction in thin coal seam. This paper analyzes the advantages and technical principles of applying the outburst elimination technology of shield tunneling in the middle roadway to block outburst elimination in thin coal seam. The gob-side entry retaining technology is adopted to make the return airway roadway of the previous working face as the air inlet roadway of the next working face. The gas extraction boreholes are constructed ahead of the air inlet roadway, and the extraction range covers and exceeds the predetermined middle roadway by more than 20 m. The gas extraction is used to eliminate the outburst danger of the middle roadway. tunneling the middle roadway. The gas extraction boreholes are constructed at the predetermined position in the middle roadway to the return airway roadway, and the extraction range covers and exceeds the predetermined return airway roadway by more than 20 m. The gas extraction is used to eliminate the outburst danger of the middle roadway. Finally, the return airway roadway is excavated to form the working face. Taking the thin coal seam of 9305 working face of a mine as the research object, the numerical simulation is carried out. The results show that when the extraction time is between 10 d and 30 d, the increase of the effective extraction radius is the largest. With the increase of the extraction time, the increase of the effective extraction range gradually decreases. When the borehole spacing is 3 m, the effective extraction radius between the two holes is almost tangent, and the extraction effect is the best. The extraction pressure can basically make most of the coal seam gas to be effectively diffused, resolved and passively extracted. The gas extraction in the middle roadway reduces the gas pressure between the return airway roadway and the progressive middle roadway area effectively. The field measurement results show that the optimal extraction borehole spacing for shield tunneling in the middle roadway of outburst coal seam in 9305 working face is 3 m, the borehole diameter is 94 mm, the effective extraction diameter is not more than 5 m, and the drilling depth is 107 m. The outburst elimination technology of shield tunneling in middle roadway reduces the gas volume fraction of the thin coal seam by about 70%, and the outburst elimination effect is remarkable.