Abstract:

When submarine tunnels are constructed by slurry shield, the seawater can enter the pressure chamber easily from the excavation surface and mix with the slurry, which would lead to change of the bleeding rate of the slurry, and further affects the properties of the filter cake and the stability of the excavation face. The slurries with different seawater additions are prepared; the bleeding rate, viscosity and zeta potential of the slurry are tested; and the void ratio and permeability coefficient of the filter cake are measured. The results show that: (1) The intrusion of seawater obviously causes the increasing of the bleeding rate and the reduction of the viscosity and zeta potential of the slurry. (2) With the increase of the amount of seawater, the void ratio of the filter cake reduces; and the permeability coefficient increases from 10-9 to 10-7 cm/s. (3) The change of slurry bleeding rate and filter cake permeability coefficient results from addition of seawater causes gradual decrease of zeta potential of the slurry and the repulsive force between the particles; macroscopically, it shows rapid precipitation and bleeding. Meanwhile, due to the increase of cations that slurry particles attract, the hydrated film becomes thinner and the effective porosity of the filter cake increases; macroscopically, the permeability coefficient increases.

Key words: slurry shield, seawater, bleeding rate of slurry, viscosity of slurry, zeta potential, permeability coefficient of filter cake