Soft and low permeability
tectonic coal seams (SLPTCSs) are widely
distributed in China. In SLPTCSs, because of the difficulty of gas
extraction, coal and gas outburst accidents occur frequently. In this
paper, with the principle of stress unloading and permeability enhancement
in SLPTCSs analyzed, it is put forward that the key technology to
realize stress unloading and permeability enhancement in SLPTCSs is
caverning by hydraulic flushing. In addition, the development of hydraulic
flushing caverning technology and equipment in China is also further
systematically studied. Field tests on the application of highly integrated
equipment for caverning by hydraulic flushing have been carried out
in the Shijiazhuang coal mine and Pingdingshan no. 8 coal mine. The
results show that the widely used drilling and hydraulic flushing
packaged equipment and drilling and mechanical cutting packaged equipment
for caverning in coal seams can efficiently enlarge caverns in SLPTCSs,
reduce the amount of workload for hole-drilling in the coal seam,
improve the permeability of the coal seam by 23.9 times, and increase
the concentration and pure volume of gas extracted in boreholes by
more than two times. Highly integrated hydraulic flushing caverning
equipment can realize high-efficiency stress unloading and permeability
enhancement of the coal seam, which provides beneficial guidance for
gas control of SLPTCSs.
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