Study on the mechanism and rapid treatment method of leakage disease at the junction between the shaft and shield tunnel

Tunnel leakage disease will seriously affect the metro operation and threaten the safety of passengers. Therefore, this study investigates the mechanism of structural leakage disease at the junction between the shaft and shield tunnel through the operational tunnel in the Beijing area. Firstly, the characteristics and intrinsic cause of the leakage are analyzed by ground penetrating radar, endoscope detection, and total station. The field inspection indicates that the water-rich cavity caused by the rise of groundwater is the main external environmental factor inducing structural leakage. The uneven deformation of the junction between the shield segments and ring beam and the deterioration of the ring beam structure are the main reasons for the waterproof layer failure, which further lead to structural leakage. In addition, numerical simulations are carried out to study the leakage mechanism of the junction structure under the effects of structural uneven deformation and ring beam deterioration. The numerical results show that the leakage caused by uneven deformation of tunnel junction is significant. Especially, the water-rich cavity near the ring beam will aggravate structural leakage. Furthermore, the deterioration of the ring beam structure has a more significant effect on the structural leakage, and the leakage mainly occurs in the ring beam and ring beam-segment joints. This finding is basically consistent with the actual leakage situation. In addition, the rapid treatment method for plugging water-rich cavities and structural defects is proposed, and a new cement-based material with good non-dispersible underwater properties is developed. The surface observation and internal detection show that the rapid treatment method effectively controls structural leakage. This research can provide a reference for future similar leakage and disease control projects of metro subways in operation.