Mechanism and modeling of infiltration of saturated sand by excavated sand-containing slurry

Abstract

During slurry pressure-balance (SPB) shield tunneling in a sand layer, the excavated sand mixes with bentonite slurry. Herein, the pressure infiltration of the saturated sand by the bentonite–sand slurry is modeled to describe the slurry and companion-water flows during the mud spurt period. A maximum infiltration-depth prediction model is also implemented, based on the principles of particle deep-bed filtration. The model closely matches experimental results for a slurry with a low sand-to-bentonite mass ratio, but tends to overestimate the infiltration distance as the mass ratio increases. Furthermore, the prediction model reflects the continuous infiltration phenomenon associated with elevated sand concentrations in the slurry. When combined with the maximum-depth prediction model, the infiltration model strongly aligns with the experimental findings for the mud spurt period. The combined model effectively explains the bentonite–sand slurry infiltration mechanism and accurately predicts mud-spurt occurrences during SPB shield tunneling in sandy layers.