Influence of geometric and rheological parameters on sealing efficiency in dual-hole grouting cases under flowing water conditions

Grouting is widely used for seepage control and rock reinforcement in underground engineering, but groundwater flow can reduce its effectiveness. This study investigates the effects of grout rheology and injection geometry on sealing efficiency under flowing water conditions using a dual-hole configuration. A three-dimensional rough fracture model is generated to represent fracture geometry in rock masses. Grout viscosity follows the shear-rate dependent Herschel–Bulkley law, while grout–water interaction is simulated via a two-phase level-set method. The effects of key geometric and rheological parameters on diffusion patterns and washout resistance are systematically analysed. Compared with single-hole injection, dual-hole grouting produces pressure-field interaction and changes the local shear rate. For Herschel–Bulkley grout, this change in shear rate leads to spatial variation in apparent viscosity and affects grout flow. Results reveal a non-linear relationship between grouting-hole spacing and grout diffusion; optimal spacing maximises pressure field coupling. Hole radius primarily controls diffusion range, whereas rheological parameters n and k govern diffusion morphology and washout resistance. Higher n and k values significantly increase the injection pressure required for effective fracture penetration. The results provide a quantitative basis for selecting geometric and rheological parameters in dual-hole grouting design.