Slurry viscosity and its effect on infiltration considering pressure effect

The slurry pressure balance (SPB) shield technique is extensively used in underground construction, with filter cake quality being critical for the stable excavation face. However, research on the impact of different slurry pressures and viscosities on filter cake formation is limited. This study assesses the microstructure characteristics of slurry viscosity. Experiments were conducted on bentonite slurries of 2253.89 and 6.81 mPa·s viscosity under slurry pressures of 25–70 kPa. High-viscosity slurry forms filter cakes with very low permeability (2.21 × 10⁻⁷–5.62 × 10⁻⁷ m/s). Low-viscosity slurry shows higher permeability (2.68 × 10⁻⁵ and 4.64 × 10⁻⁵ m/s) at slurry pressure of 25 and 40 kPa, but permeability drops (8.72 × 10⁻⁷ and 2.61 × 10⁻⁶ m/s) at slurry pressure of 55 and 70 kPa. Based on these findings, this paper proposes using low-viscosity slurries with high pressures for hypotonic, structurally stable filter cakes in SPB shield tunnelling. This offers practical insights into safer, more efficient operations and could enhance construction safety and efficiency.