Dynamic modeling of air cushion chambers in large-diameter slurry shields: A case study

In the context of large-diameter slurry shield tunneling, the stability of the excavation face and the safety of construction operations are critically influenced by the dynamic interaction between slurry and air within the air cushion chamber. Despite advancements in slurry shield technology, research on parameter optimization for the air cushion chamber—such as initial air pressure, slurry level, and pneumatic stiffness parameters—remains underexplored, frequently resulting in operational instabilities. This study utilizes mathematical modeling to analyze the air-liquid coupled support mechanism in the slurry chamber of large slurry shield machines. Using the Herrenknecht air cushion slurry shield deployed in the Qingdao Jiaozhou Bay Second Undersea Tunnel project as a case study, dynamic models incorporating slurry pressure equations, mass-spring-damper system, and nonlinear pneumatic stiffness were developed. MATLAB-based simulations were performed to evaluate the effects of slurry level variations on key system parameters, including pneumatic stiffness, damping coefficients, and vibration transmission ratios. The findings reveal a nonlinear relationship between pneumatic stiffness and slurry level, with distinct regions of stability and critical thresholds where abrupt stiffness changes occur. The study further demonstrates that damping coefficients increase with slurry levels, reflecting enhanced energy dissipation under higher slurry level, and identifies optimal slurry levels for minimizing disturbance loads and avoiding resonance. The buffering role of air cushion chambers in mitigating pressure fluctuations is also verified. The buffering role of the air cushion chamber in mitigating pressure fluctuations is also verified. Field validation confirms that the theoretical model reliably captures pressure trends during tunneling. The study contributes a robust modeling framework and practical insights for optimizing air cushion chamber parameters, enhancing excavation face stability, and improving large-diameter slurry shield operations. • A dynamic model of air-liquid interaction in the slurry chamber of large-diameter slurry shields was developed. • The nonlinear relationships between pneumatic stiffness, slurry level, and damping coefficients were analyzed. • The effects of slurry level variations on system stability and pressure fluctuations were evaluated. • A theoretical model was validated using field data to optimize air cushion chamber parameters for tunneling efficiency.