【正文】 We planned to bine mining the 21511 working face in East1 and the 23521 in East2 and called the bination 23521 instead The strike of the face is 1640 m and the trend 190 thickness of the coal seam is between ～ m, m on average and the dip angle 60130, 90 on average. The amount of gas of the B11 coal seam is , designed for 2000 t/d.The C13 coal seam is a protected layer, located 70m above the B11 coal seam. The corresponding test working face of the protected layer consists of the 21213 working face in East1 and the 23223 in East2 (called 21213/23223 bined). The strike is 1680 m (two faces in all) and the trend is 160 coal seam is ～ m thick, m on average,the dip angle 60～130 and 90 on average. The original measured gas pressure was MPa, the amount of gas (). The coal seam was also stable and its geological structure simple. By draining the pressure relief gas, the danger of outbursts in the C13 coal seam could be eliminated and the amount of gas was effectively prehensive，mechanized cover caving coal mining technology been adopted for this working face, which was signed for 5000 t/d.3 Drainage principle of pressure relief gasDraining of pressure relief gas is referred to as protective layer mining technology. When we mine coal seams in outburst coal mines, we should first mine the nonoutburst or low risk outburst coal seams as protective layers, where the outburst coal seam is then called the protected layer. With protective layer mining, the coal and rock mass among the roof and floor moves and deforms within certain limits,which causes stress changing. Fracture fields are redistributed, ground stress is reduced, the coal seam expands, the coal seam permeability coefficient increases and drainage condition are created for pressure relief gas in the protected coal seams. In the case of the Panyi mine, we drilled penetration boreholes or carried out surface well drilling to drain the pressure relief gas, which caused the amount of gas and pressure to decrease significantly and the coal mass turned hard. Naturally. eas pressure reduced to below , the amount of gas reauced to below a 6m3/t and the coal consistency coefficient rose 48%100%.At the end, the danger of outbursts was pletely eliminated from the protected layers and conditions for safe and highly efficient mining had been achieved. Drainage indices of pressure relief gas in the different ore areas are shown in Table 1.4 Drainage methods of pressure relief gasDrainage methods of pressure relief gas consist largely of draining gas from the protected layers affected by mining. The space between the protective working faces 23521 and 21213/23223 was about 70 m, which is really a long distance below the protective layer mining. We have often used surface well drilling and upper penetration boreholes located in floor roadways to drain pressure relief gas from the underside of the protective mining layer. Surface well drilling is unreliable and we often used penetration boreholes. The design of penetration boreholes includes the construction of a floor roadway, a suction drilling field and upper penetration boreholes when 80 m away, the pressure sharply decreased, and at 62 m the pressure gauge finger pointed to zero. When the protective working face advanced 400m past the pressure measured hole, the pressure value increased from zero to MPa and remained stable, which indicated that the residual gas pressure was . Outburst danger eliminated analysis of the protected layerThe amount of gas in the protected layer is decreased by draining the pressure relief amount of residual as of the C13 coal seam was reduced to and the residual declined to MPa. The amount of gas pressure values were lower than the critical value, which was 8m3/t for the amount gas and (pressure gauge) for gas this shows is that C13 coal seam had changed from a high gas and outburst coal seam to a low nonoutburst coal and C13 became a safe and highly effective coal seam where mining conditions became considerably better, as proven by its current mining practice.7 Conclusions1) With the advancement of a working face, coal and rock masses among