Analysis of curtain slurry diffusion pattern and interception effect in inclined shafts in dynamic water sanding zone

Typical hidden engineering characteristics exist for mining curtain grouting, especially in the complex geological conditions of inclined shaft over moving water sanding area, there is a greater blindness in the determination of its technical parameters. The study of curtain interception mechanism and key technical parameters in dynamic water sandy area is of great significance for water control in inclined shafts of coal mines in western China. Caojiatan coal mine sandy area sloping shaft curtain grouting as the background of the project, established a slurry diffusion model of moving water sand layer considering the time-varying slurry viscosity and long-term coupling of percolation effect, explored the influence of moving water flow rate and grouting pressure on the radius of grouting diffusion of the sand layer, elucidated the response of the groundwater flow field of the sloping shaft curtain area with different curtain thicknesses, and determined the distance between the grouting holes of sloping shafts in the sandy area of the moving water and the thickness of the curtains. The results show that: (1) Under the condition of grouting in the dynamic water sand layer, the spreading pattern of the slurry in the horizontal direction is "ellipsoid-like", and in the vertical direction is "tornado-shaped". When the dynamic water flow rate increased to 0.2 m/s, the single-hole grouting against the water direction could not be effectively cemented and sealed. (2) Increasing the grouting pressure can offset the scouring effect of moving water to a certain extent. However, when the grouting pressure is increased to 0.5 MPa, the increase in the spreading distance of the slurry decreases due to the influence of the grouting characteristics of the sand layer. (3) With the increase of curtain thickness, the influence range of groundwater flow field in the curtain area of the inclined shaft decreases, the water level decreases significantly, and the surge volume shows a negative exponential downward trend. (4) Combined with the actual engineering, the curtain grouting holes and row spacing of 2.0 m and the minimum safe curtain thickness of 6.0 m were determined for the sloping shaft in the dynamic water sanding area. The field industrial test shows that the core rate of the treatment area is >80%, the water influx attenuation is 85.6%, the slurry consolidation degree is high, and the curtain interception effect is remarkable, which verifies the reasonableness of the selection of key technical parameters. The research results can provide theoretical basis and practical reference for similar projects.