Abstract
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 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. The blasting models under different blasting parameters were established by ANSYS/LS-DYNA software. The influence radius of single-hole blasting was 3.1 m, the hole diameter of double-hole blasting was 113 mm, the hole spacing was 5.5 m, and the delayed blasting time was 25 ms. According to the numerical simulation results, the determined parameters were tested on the working face of the 1312 transportation roadway in coal seam #3 of the Sanyuan coal mine. The results show that after blasting, the permeability of the original coal seam was increased by more than 30 times, the gas concentration was increased by 2.16 times, and the single hole purity and mixing volume were increased by 4.73 and 4.27 times, respectively. The positive effects of deep hole presplitting blasting permeability enhancement technology on the pressure relief and permeability enhancement of a low pressure and high gas coal seam were determined.
Highlights
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
Research on deep hole presplitting blasting in high gas coal seams began in the last century
The results show that the stress wave can help the extension of primary fractures and accelerate the generation of a small number of new cracks, which plays a role in pressure relief for enhancing the permeability of the coal seam
Summary
Coal rock density Elastic modulus Poisson’s ratio Tensile strength Compressive strength Cohesion. Combined with the actual situation of the site, a group of deep hole presplitting blasting effective radii was constructed in the 1312 working face to investigate the measuring points. The results show that the attenuation intensity of gas emission decreased by 67.65% after the implementation of deep hole presplitting blasting on working face 1312 This means that the permeability enhancement of presplit blasting changes the pore structure of the coal, which is conducive to continuous gas extraction. After the implementation of deep hole presplitting blasting permeability increasing technology, the single hole gas purity of observation boreholes #10, #12, and #13 varies from 0.080 to 0.137 m 3·min-1. The results show that new irreversible cracks are produced by presplitting blasting This shows that deep hole presplitting blasting technology is effective in promoting gas drainage in the Sanyuan coal mine
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