Numerical and experimental study of diffusion law of foamed polymer grout in fracture considering viscosity variation of slurry

• A numerical method of grouting considering rheological characteristics is proposed. • A set of visual parallel plate crack polymer grouting test device is established. • The time-varying viscosity of slurry is the cause of pressure lag effect. As a new type of chemical grouting material, polymers have been widely used in fractured rock masses, but the understanding of the diffusion characteristics of polymers still needs to be further improved. Due to the expansion of polymer slurry, the change of grouting pressure is not synchronized with the time change of diffusion radius, leading to the diffusion law of polymer slurry more complicated. Therefore, based on the rheological properties of the slurry and the theory of viscous hydrodynamics, a polymer fracture grouting diffusion model was established. Through the finite element level set method and adjusting the liquid level according to the fluid velocity, it can be obtained the diffusion interface of the fluid at the corresponding point in time and the change law of the pressure at the corresponding diffusion interface with time. Finally, the validity of the model is verified by the polymer slurry parallel plate grouting diffusion experiment. The research results indicated that: (1) The diffusion mode of the polymer fracture grouting diffusion model is basically consistent with the test results. (2) The grouting pressure gradually decreases along the direction of the diffusion radius, increases with the decrease of the crack width, and increases with the time, but the change of the grouting pressure lags behind the change of the diffusion radius. (3) The results are consistent with the pressure field curve measured by the experiment, indicating that the main factor causing the hysteresis effect of the pressure field change is the time-varying viscosity of the polymer slurry.