What is the purpose of the Bentonite slurry used in some TBM operations?

Bentonite slurry serves several critical purposes in certain TBM operations, most notably in Slurry TBMs. Primarily, it provides face support. The slurry is pumped into the excavation chamber to balance the earth and water pressures acting on the tunnel face, preventing collapse or instability. It also forms a filter cake. As the slurry permeates the soil or rock around the excavation face, it deposits a thin layer o....