Key technical equipment and engineering practice of long borehole fracturing prevention and control in thick and hard roof rock burst underground

Aiming at the problem of prevention and control of rock burst induced by thick and hard roof, breaking through the traditional local pressure relief treatment mode, the key technology and equipment of underground long borehole fracturing are studied, and the roof weakening transformation system with advanced space-time coordination is established. Based on the theory of “geology-stress-energy” synergy, the research method of combining theoretical modeling, equipment development and engineering verification is adopted. By constructing three-dimensional identification model, developing directional drilling equipment, innovating fracturing process parameters, developing monitoring and evaluation system and other technical paths, the research on hydraulic fracturing prevention and control technology for thick and hard roof is systematically carried out. The research shows that: ① The three-dimensional identification model of “geological structure-stress field characteristics-energy accumulation degree” is established to realize the multi-dimensional quantitative identification of the fracturing target layer. ② The developed ultra-high-position hole-forming platform with variable amplitude and large dip angle can adjust the dip angle to 50°, increase the hole-forming efficiency by more than 20%, the hole depth can reach 1000 m, and the profile height can reach more than 100 m. ③ The low-speed and large-flow fracturing pump group (displacement 2.8 m³/min, pressure 80 MPa) and multi-parameter monitoring system are developed to realize the dynamic control of fracturing process. At the same time, an online monitoring equipment system is built to realize the scientific and comprehensive evaluation of the whole cycle of fracturing system monitoring and treatment effect. ④ The engineering test was carried out in the typical roof strong-impact mine of Nalinhe No.2 Mine. After the treatment, the stress of the coal body decreased by more than 60% compared with the adjacent working face. The frequency and energy of large energy microseismic events are about 70% lower than those in the ungoverned areas and adjacent working face, and the periodic weighting step is shortened by more than 25%. From the multi-scale synergistic mechanism of elastic strain energy dissipation of fracturing fracture network, shortening cantilever to reduce fracture kinetic energy, layered collapse to block kinetic energy transfer path and high-pressure water rock weakening, the mechanism of “energy dissipation-structure regulation-path blocking-strength weakening” pressure relief and disaster prevention of directional long borehole multi-stage fracturing with thick and hard roof is discussed. It is pointed out that the development direction of constructing an intelligent optimization platform for digital twin fracturing parameters and developing intelligent fracturing complete sets of equipment, and puts forward a new idea of transforming a single disaster prevention mode to “precise identification-intelligent control-multi-disaster joint prevention”.