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 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.
Highlights
Coal seam gas predrainage technology is considered to be one of the most effective measures to prevent coal mine gas disasters [1]
Aliabadian and Sharafisafa [10] investigated the effect of presplitting on the generation of a smooth wall in a rock domain under the blasting process in a continuum rock mass
Valiappan et al [12] analysed and discussed the detailed situation of rock blasting by using the finite element calculations program software
Summary
Coal seam gas predrainage technology is considered to be one of the most effective measures to prevent coal mine gas disasters [1]. The deep-hole presplitting blasting permeability increasing technology can produce multiple cracks in the coal body of a low permeability coal seam forming an underground fracture network channel, which can greatly improve the gas drainage efficiency and reduce or even eliminate the hidden dangers in the gas mining process [2,3,4,5]. Erefore, in view of the technical problem of difficult gas drainage in the 1312 working face of coal seam #3 in the Sanyuan coal mine of China, a new technology of deep-hole presplitting blasting with millisecond blasting as the core is proposed by using solid fluid coupling method, and the blasting scheme is optimized by simulating different millisecond blasting time intervals. If we do not consider the existence of gas in the coal seam and only study the coal and rock mass as a single solid medium, some errors exist compared to the actual situation. erefore, in view of the technical problem of difficult gas drainage in the 1312 working face of coal seam #3 in the Sanyuan coal mine of China, a new technology of deep-hole presplitting blasting with millisecond blasting as the core is proposed by using solid fluid coupling method, and the blasting scheme is optimized by simulating different millisecond blasting time intervals. e results of field test and comparative analysis show that the blasting has achieved the expected effect, which has a certain reference significance for the gas control of similar coal mines in the same area
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