Influence of Advance and Retreat High-pressure Water Jet Slotting on Coal Seam Depressurization Antireflection Effect

High-pressure water jet slotting technology was the main measure of single low permeability coal seam depressurization antireflection technology, it carried out hydraulic slotting inside the coal seam by penetration drilling slotting in coal seam, thus it flushed the part of coal, changed the stress situation around the borehole, and destroyed the internal balance of coal seam, increased coal seam permeability. Based on different slotting technology effect, it analyzed the effects and characteristics of advance and retreat slotting for coal seam depressurization antireflection, and obtained the slotting technology which was in accordance with different coal mine situations. It was irritable inside the borehole in advance slotting process, which was suitable for little thickness coal seam, while it was gentle inside the borehole in retreat slotting process, which was suitable for large thickness coal seam.