Study on hydrodynamic diffusion law of the swelling particle slurry in karst pipeline

The swelling particle grouting material has demonstrated remarkable plugging effectiveness in high-pressure and large-flow burst water within karst pipelines. Currently, current research on the rheological model, flow computation theory, and plugging mechanism of this material is lacking. The conventional grouting slurry diffusion process, using the liquid-liquid two-phase flow method, fails to accurately simulate high solubility slurry and particle swelling. To address these limitations, this study established a precise constitutive model to describe the swelling particle slurry diffusion process in dynamic water. Additionally, a coupling calculation method was proposed to analyze the spatiotemporal heterogeneity of viscosity during slurry diffusion by considering the migration of slurry and the changes in viscosity. To investigate the interaction between particle swelling and flow field changes, a Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) coupling model was developed for the diffusion of swelling particle slurry. It is demonstrated that slurry viscosity increases exponentially within the diffusion front as the particle swelling rate rises, and the drag force exhibits an intriguing behavior of initially increasing and then decreasing as the slurry flows through the pipeline. Furthermore, the CFD-DEM coupling model proved to be more accurate in describing viscosity distribution and diffusion distance compared to the finite element solution. The primary objective of this paper is to reveal the plugging mechanism and provide theoretical support for the engineering application of the swelling particle grouting material.