Infiltration Model of Rheological Bentonite Slurry through Sands

Abstract

Bentonite grouting is utilized widely in geotechnical engineering to stabilize the excavation and prevent seepage in sandy soils. However, the infiltration behavior of bentonite slurry in sandy soil is not well understood, primarily due to rheological blocking and the formation of a filter cake. This study performed infiltration column tests to investigate the infiltration behavior under various conditions, including slurry concentration, sand properties, grouting pressure, and infiltration duration. Monitoring included infiltrated distances (calculated from drainage volume), pore pressure at different depths, and bentonite distribution using methylene blue titration. Results indicate that rheological blocking occurs during the infiltration process as bentonite slurry, which is a shear-thinning fluid, increases in viscosity with a decreased shear rate. This phenomenon is more pronounced with higher slurry concentrations, leading to reduced infiltration distances. Additionally, in soils with pore throats smaller than bentonite particles, a filter cake forms above the surface of the grouted soil, decreasing the pore pressure and further reducing infiltration distance. The distribution of bentonite content remains consistent across the infiltrated zone, resulting in a linear pressure drop. Based on these findings, the study proposes a novel model that combines the generalized Darcy’s law, the Herschel–Bulkley rheological model, and mass conservation of slurry to predict the spatiotemporal progression of the infiltration front. This model, which was validated using experimental data, accurately predicts the effects of rheological properties and filter cake formation on infiltration. The results of this study provide valuable insights into infiltration processes and enhance the application of bentonite slurry in grouting.