Simulated study on the grout-rock coupling mechanism and impermeability of chemical grouting materials in a single fracture.

Grouting in fractured rock masses is crucial for seepage prevention and reinforcement in underground engineering, yet the process remains poorly understood due to its concealment and complex grout-rock coupling. Using a self-developed visualization system, this study simulated grouting in a single planar fracture with four chemical grouts: acrylate, modified urea-formaldehyde, epoxy, and polyurethane. The entire process-including diffusion patterns, pressure evolution, fracture deformation, and post-curing seepage-was monitored, revealing the coupled seepage-deformation mechanisms during grouting, secondary migration, and stabilization. Under the grouting parameters used in this study, the results indicate that: under the 0.1 mm initial fracture aperture, polyurethane and acrylate diffuse best, epoxy worst. All grouts underwent secondary migration; polyurethane's area expanded 160.7% (active expansion), others increased 34.3-77.6% (passive decay). Fracture grouting comprises injection, secondary migration, and stabilization stages. Impermeability varied: epoxy had high initial breakthrough pressure but dropped sharply; polyurethane showed adaptive cycles; modified urea-formaldehyde had high breakthrough but low stable pressure; acrylate had low peak pressure and reversible deformation but insufficient stiffness. This work provides a basis for material selection and process optimization.