Experimental study on property change of slurry and filter cake of slurry shield under seawater intrusion

Abstract

During submarine tunnels construction by the slurry shield tunneling method, seawater may enter the pressure chamber from excavation surface and mix with the slurry. This will cause the physical stability of the slurry to change and will also affect the properties of the filter cake and the stability of the excavation surface. This study aims to investigate the effect of seawater on the properties of the slurry and the filter cake using laboratory experiments. Mixtures of slurry and seawater in different ratios were prepared and the physical stability, viscosity, and zeta potential of the slurries were tested. The basic properties and microstructure of the filter cake formed by the different slurries were also investigated. The results showed that the intrusion of seawater significantly reduced the physical stability and the zeta potential of the slurry. As the seawater content in the slurry was increased, the void ratio in the filter cake formed by the slurry decreased and the filter cake permeability coefficient increased from 10−8 cm/s to 10−7 cm/s. In the filter cakes formed by slurries containing some seawater, soil particles in aggregates were more tightly packed with more intra-aggregate pores and better connectivity than the seawater-free filter cake. The decrease in zeta potential was the fundamental reason for both the slurry’s change in physical stability and the changes in filter cake properties.