Application and Mechanism on pressure relief and permeability enhancement of diamond beaded wire saw cutting in low-permeability coal seam

In order to explore the mechanism of seam pressure relief and permeability enhancement of diamond beaded wire saw cutting in coal seam, combined with the engineering background of wire saw cutting seam in Kailuan Mining Area, similar simulation tests are used to study the distribution characteristics of fracture, the seam cracks and stresses of the upper and lower coal seams of the wire saw coal seam,the stress-permeability formula of coal sample with three isobaric cycles under loading and unloading was established, and a calculation program of coal seam gas permeability was developed based on FLAC3D and the distribution characteristics and evolution law of permeability coefficient of coal seam above the seam slot in the process of wire saw cutting were studied by using numerical simulation method.The seam cutting system and technology of diamond wire saw have been developed, and a large-scale continuous seam cutting test has been carried out. Research results show that after cutting coal seam with diamond beaded wire saw to form seam slots, a small range of fracture zones and curved subsidence zones are formed above, and a stress reduction zone is formed in the upper and lower overburden rocks. The stress variation amplitude decreases as it stays away from the slot; a certain range of anti-reflection zone is formed above the slot, which is characterized by a large increase of permeability near the starting position and the stopping position, and a small increase of permeability in the middle part penetrates due to the effect of stress recovery.The permeability above the slot gradually decreases with the increase of the distance to the slot. When it reaches a certain threshold, the slitting will lose its effect on increasing the permeability. The cutting efficiency of diamond wire saw is about 80 m2/h, and the working efficiency and continuous cutting range are greater than hydraulic slotting measures.