Abstract:

Water outbursts represent one of the primary geological hazards in underground engineering. Traditional grouting materials exhibit poor retention rates and weak erosion resistance, resulting in inadequate sealing effectiveness. To address this, the team independently developed a modified cement-based magnetic grouting material. Magnetic adsorption properties and SEM analyses were conducted to investigate the influence of magnetic powder dosage on magnetic adsorption performance. The study revealed the cementitious hardening mechanism at the microscopic level, where additives synergistically regulate cement particle dispersion and accelerate hydration processes. Through pipe-type fissure water ingress sealing tests, the pressure variation pattern—the "gradual increase-abrupt surge-sudden drop-stabilization" time-varying pattern—under different magnetic powder dosages, sealing section lengths, and magnetic induction intensities was systematically investigated. Results indicate that increasing magnetic induction intensity from 0.289 5 T to 0.526 5 T enhances magnetic adsorption performance by 28.12%; under identical conditions, raising magnetic induction intensity from 0.412 3 T to 0.526 5 T increases sealing water pressure by 24.7%; and increasing the magnetic powder content from 20% to 40% boosts the plugging water pressure by 38.5%. By coupling the magnetic field force with the Navier-Stokes (N-S) equation, a prediction model for water outburst plugging under magnetic field influence was established. The theoretical peak plugging pressure value exhibited an error of less than 9% compared to the experimental value. This model provides valuable guidance for refining the theory and engineering application of magnetic slurries.

Key words: pipe-type fissures, water inrush plugging, magnetic slurry, magnetic induction intensity