Experimental Study on Coal Seam Fracturing Based on Hydrodynamic Horizontal Slitting-CO ₂ Blasting Collaboration

With the deepening of coal mining depth, the geological conditions of coal seams become more and more complicated, and the effect of single gas permeability enhancement technology in practical engineering applications is not ideal. To address the limitations of the single coal seam permeability enhancement technology, this paper takes the No.9 coal seam of a coal mine in Guizhou as the research object and puts forward a gas-liquid two-phase comprehensive action coal seam permeability enhancement technology. The hydraulic horizontal slitting technology is used to create a free surface for pressure relief and then the CO₂ fracturing and permeability technology is used to synergize the pressure relief and permeability of the coal body. By analyzing the crack expansion of similar models through simulation experiments and examining the characteristics of displacement field distribution on the model surface using digital image correlation techniques, COMSOL Multiphysics was utilized to analyze coal body displacement and validate the simulation experiments. The results show that the delamination cracks generated between the roof slab and the coal seam inhibit the radial crack extension of the coal seam. The y-axis displacement values above the slit show regular changes, gradually decreasing from the center to both sides, while the displacement values below the slit remain essentially unchanged. The unpressurized free surface created by the hydraulic horizontal slit left the coal body above unsupported, resulting in the formation of a large number of horizontally expanding cracks as well as radially expanding cracks. CO₂ blasting further perturbed the internal coal body, inducing crack expansion and generating numerous new radial cracks. Together, these processes formed a complex crack network. The hydraulic horizontal slit-CO₂ blasting gas-liquid two-phase integrated action permeability enhancement technology provides a novel approach for the efficient mining of deep coal seams.