Numerical analysis of pulsed grout injectability in fractured rock mass considering grout-rock coupling and spatiotemporal rheological evolution

In deep fractured rock masses with high in-situ stress and groundwater, constant-pressure or constant-flow grouting struggles to drive grout over long distances in micro-fractures. To address the limited treatment of grout rheological evolution and grout-rock coupling in existing models, this study develops a pulsed grouting diffusion model for a single fracture based on the Bingham constitutive law and the Goodman fracture deformation model. The model incorporates spatiotemporal heterogeneity in grout reaction degree, pressure-aperture coupling and unsteady pulsed boundary conditions, and is solved using the finite volume method with reaction-degree mapping and pressure-aperture iteration. The results show that pulse frequency increases diffusion radius by delaying rheological blockage through yield-threshold rectification, whereas pulse amplitude increases total grout volume through cubic-law amplification and elastic release. Rock normal compliance is positively correlated with grout volume, while the fracture dilation threshold pressure causes competition between grout volume and diffusion radius. The model provides a basis for optimizing pulsed grouting parameters in fractured rock masses.