Abstract: The existing mud cake prevention and control schemes for slurry shield tunneling in highly viscous formations are purposeless and inefficient. Existing studies do not distinguish the mechanical differences between two application scenarios: preventing mud cake formation and treating already formed mud cakes. To address these issues, a dual-path prevention-treatment cooperative control method based on dispersants is proposed. Nine types of dispersants commonly used in shield tunneling, including organic types (e.g., Sodium Lauryl Ether Sulfate and Sodium Lignosulfonate) and inorganic types (e.g., Polycarboxylate and Sodium Hexametaphosphate), are selected. Their efficacy is systematically evaluated through a dual-path prevention-treatment experimental design. In the prevention path, a stirring adhesion test is used to simulate the dynamic shear at the cutterhead, and the adhesion rate is used to quantify the inhibition effect. In the treatment path, mud cake disintegration tests combined with adhesion force measurements are conducted to analyze disintegration capability and the reduction of residual adhesion force. The study systematically reveals the differential influence patterns of dispersant type and its optimal mass fraction in the two scenarios. The results indicate the following: (1) In the prevention stage, the anionic surfactant Sodium Lauryl Ether Sulfate (SLES, 1.0%) and the polymer dispersant Polycarboxylate (PCAC, 1.0%) significantly reduce the adhesion rate to 10.8%－15.0%, with a general efficacy threshold observed when the concentration exceeds 1.0%－2.0%. (2) In the treatment stage, the PCAC-SLES composite (1:1) exhibits a synergistic effect, increasing the mud cake disintegration rate to 69.14% (22.52%－26.03% higher than individual components) and reducing the residual adhesion force by 82.33%, while clarifying the synergistic effects and cost-benefits under different compounding ratios. Mechanism analysis shows that dispersants significantly promote clay dispersion by enhancing electrostatic repulsion and steric hindrance effects.

Key words: slurry shield, mud cake on cutterhead, dispersant, mud cake prevention, mud cake treatment, adhesion force, Zeta potential