Application of new thin-layer spraying material in shotcreting fire prevention of final mining line

The traditional spraying materials used for surface closure of coal mine roadway are poor in toughness, easy to crack, easy to fall off, and the blocking effect is poor. To end this, this paper developed a new type of thin spray material for mining, which was mainly based on "VAE emulsion with a fixed water-cement ratio of 50% and a poly-ash ratio of 15%", supplemented by "light calcium carbonate, cellulose, and accelerator", and obtained the best thin spray parameters through spray test. A field test of thin-layer spraying was carried out in the 21802 measure roadway (the final mining line retaining) in Qinglong Coal Mine. The application results show that: when the maximum displacement of the top and bottom plates is 380 mm and the maximum displacement of the two sides is 91 mm at 90 days after gob-side entry by cutting roof, the thin-layer spray coating remains intact; after the roadway is completely sprayed, the air leakage rate is reduced from the maximum 39 m³/min to about 10 m³/min, and the air leakage rate is greatly reduced; with the continuous expansion of the shotcrete range, the CO volume fraction in goaf near the final mining line gradually decreases, and finally maintains at a low level, preventing the spontaneous ignition of the coal left in the final mining line.