Effects of the CADW in low-metamorphic coal and analyse on its action mechanism

The CO2-alkaline-water two-phase displacing gas and wetting coal (CADW) measure can effectively prevent coal and gas outburst and reduce mine dust concentration, while relevant research on its effects and action mechanism is insufficient. In this work, effects of the CADW in low-metamorphic bituminous coal and its action mechanism were investigated deeply. The experimental results revealed that, after using the CADW, the risk of gas outburst was reduced evidently compared with conventional water injection. The residual methane and mixed gas in JZ coal reduced by -79.50% and -33.39% severally. The water-injection effect was also enhanced obviously. During injecting water, the maximum pore pressure at 20, 40, 60 mm away from the drilling increased by 10.80%, 5.96%, 1.80%, respectively. The water-injection rate, total volume and radial moisture content of JZ coal all increased distinctly, with the increment of 4.45%-28.14%, 10.30% and 3.45%-15.82% respectively. The increment of moisture content rose with distancing the drilling. In addition, the CADW could notably improve the water-lock effect, the permeability of JZ coal was reduced by 88%. As a result, the methane migration, from deeper coal seam to the exposed working face, was inhibited effectively. The results can provide significative guidance for the application of the CADW technique, gas outburst prevention and dust concentration reduction.