Airtightness failure analysis of filter cake during shield tunneling machine hyperbaric intervention

Abstract

During shield tunneling in areas of high groundwater or soft ground, the hyperbaric intervention method is widely used to access the excavation chamber of the TBM to perform inspections and repair cutters. The airtight capability of the filter cake is the key to safety in the hyperbaric intervention. If the airtightness of the filter cake fails, the compressed air can escape into the crevasses of the soil and rock rendering the face unstable. This paper focuses on the airtightness failure behavior of the filter cake under air pressure. A multiphase flow-evaporation coupling model is developed to assess the failure of airtightness and the permissible pressure maintenance time during compressed air operations. The proposed model is validated by the airtightness test of the filter cake in the laboratory. The results show that the external filter cake plays a primary role, while the infiltration zone plays an auxiliary role in the effective airtightness mechanism of the filter cake. The proposed model can be applied to evaluate the duration of airtightness during maintenance work. The findings of this study have significant implications for ensuring the safety of the tunnel face during hyperbaric interventions in slurry TBM operations.