Relieving Pressure and Improving Permeability of Soft Coal at Top and Bottom by Hydraulic Cavitation

Mine in China as the engineering background, the technology of
hydraulic cavitation at the top and bottom of soft coal (HCTBSC)
with low permeability was put forward. FLAC3D was utilized to build
the calculation model, and Tecplot was employed to process data of
the results, revealing the characteristics of stress variation in coal
seam for different cavitation radius and different distribution forms
of cavitation. The field test scheme of HCTBSC was determined to
verify the simulation results. Results show that the effectiveness of
stress relief (ESR) is controlled by the cavitation radius and
cavitation distribution forms. The dimension of pressure relief
emanates via the cavitation elongating outward with the cavitation
radius, and the stress changes in the coal are different due to different
cavitation distribution forms. The field test proves that the
technology of HCTBSC is more effective in relieving pressure,
increasing the productiveness of gas extraction, and decreasing the
scourge of coal and gas protrusion. The obtained conclusions in this
study provide guidance for the hydraulic cavitation application in soft
coal.