ABSTRACT
Bentonite slurries are commonly used for tunnel face stabilization during slurry shield tunneling. In highly permeable soils uncontrolled slurry flow into the adjacent soil can cause loss of support and ultimately lead to a collapse of the tunnel face. In this contribution, innovative slurry flow tests were carried out to investigate slurry penetration in coarse soils, considering the influence of the slurry, the soil and the applied fluid pressure. Experimentally, a clear correlation between the slurry penetration, fluid pressure, rheological properties of the slurry and permeability of the soil was observed. Based on the 1D-Navier-Stokes equation, a semi-analytical model to estimate the slurry penetration in coarse soil as a function of the characteristic shear resistance of the slurry determined with a rheometer, the soil permeability and the fluid pressure was derived. The experimental results indicate that using appropriate bentonite-filler mixtures slurry shields become feasible, even in very highly permeable soils.
