Study on the Technology of Enhancing Permeability by Millisecond Blasting in Sanyuan Coal Mine

To reduce gas disasters in low permeability and high-gas coal seams and improve gas predrainage efficiency, conventional deep-hole presplitting blasting permeability increasing technology was refined and perfected. The numerical calculation model of presplitting blasting was established by using ANSYS/LS-DYNA numerical simulation software. The damage degree of coal and rock blasting was quantitatively evaluated by using the value range of the damage variable D. According to the actual field test parameters of coal seam #3 in the Sanyuan coal mine, Dlim = 0.81–1.0 was the coal rock crushing area, Dlim = 0.19–0.81 was the coal rock crack area, and Dlim = 0–0.19 was the coal rock disturbance area. By comparing and analysing the damage distribution nephogram of coal and rock mass under the influence of different millisecond blasting time interval and the blasting effect of simulation model, the optimal layout parameters of multilayer through cracks were obtained theoretically. And, the determined parameters were tested on the working face of the 1312 transportation roadway in coal seam #3 of the Sanyuan coal mine. The permeability effect was compared and analysed through the analysis of the gas concentration, gas purity, and mixing volume before and after the implementation of deep-hole presplitting blasting antireflection technology, as well as the change of gas pressure, attenuation coefficient, permeability coefficient, and other parameters between blasting coal seams. The positive role of millisecond blasting in reducing pressure and increasing permeability in low permeability and high-gas coal seam were determined.