Experimental Study on Characteristics of Filter Cake Formation in Slurry Shield Tunnelling Based on “Cutter-Soil” Interaction

In recent years, more and more river-crossing and sea-crossing underwater tunnels have become the first choice for the construction of large channels in regions with developed river system. Relying on its superior pressure control mode and high security, Slurry Pressure Balance shield (SPB) is widely used in the construction of underwater tunnels with large cross-sections. The filter cake is an important medium to guarantee the stability of the excavation in SPB tunnelling. However, the mechanism of cutter on soil and filter cake (the interaction of “cutter-soil”) are still unclear. In this study, a self-made test apparatus based on the interaction of “cutter-soil” is presented. The experiment results revealed that “cutter-soil” interaction, compared to cases without the interaction, reduced the impermeability and effective stress conversion rate of filter cake, which is unfavorable to guarantee the stability of the tunnel face. To overcome this problem, two methods were proposed: continuous injection of slurry with different densities and increasing the coarse particles of slurry. It is shown that the methods have improved filter the impermeability of cake formation, which contributes to the stability of the shield excavation face.