Research on the migration patterns and termination pressure of grouting slurry in horizontal boreholes within deep limestone aquifers

Because the law of slurry diffusion in horizontal grouting holes in deep limestone aquifers is unclear, and the key grouting parameters in grouting design and engineering practice lack a theoretical basis, the grouting process cannot be effectively controlled, and the grouting effect cannot be guaranteed. Therefore, this study comprehensively adopts laboratory tests, theoretical derivation, numerical analysis, comparative verification, and numerical simulation to study the influence characteristics of the theoretically calculated slurry diffusion form and inclination angle, which are similar to those of the physical model test and numerical simulation results. Under different grouting pressures, fracture inclinations (excluding 0°), fracture openings, and slurry water-cement ratios, the slurry diffusion form was approximately oval and symmetrical along the central vertical line, and the maximum and minimum slurry diffusion distances appeared at azimuths of 180°and 0°, respectively. The range of the slurry diffusion trace increased and decreased with an increase in the fracture dip angle in the lower and upper fractures, respectively. Under the same conditions, the slurry diffusion distance in the crack above the horizontal grouting hole was greater than that in the crack below. The crack initiation pressure decreased with an increase in the crack length (0.01-0.5 m), and the decreasing range increased with an increase in the maximum principal stress. Under the same maximum principal stress, the cracking pressure decreases with the increase of crack length. When the crack length is 0.01-0.5 m and the maximum principal stress is 15-25 MPa, the cracking pressure at the top of the Ordovician limestone is 16.73-27.85 MPa. The research results are helpful to provide theoretical support and basis for the practice of grouting reconstruction in the advanced area of karst fractured aquifer in the floor of North China coalfield.