Investigation of Water Leakage of Metro Segments Caused by Metro Underpass Structures

Water leaking into metro segments is related directly to the presence of underground water. However, to date, the underground confined water channels formed by metro underpass reinforcement structures have not been considered as causes of the problem. In the present study, based on field investigations and geological data, confined water is identified as the source of segment leakage on Line 5 of Hangzhou Metro in China. It is then hypothesized that the problem stems from an underground confined water channel formed under the reinforced structure of the subway. Numerical simulations predict a settlement difference of 8–10 mm between the reinforcement area and the weak strata, and field monitoring data show this difference to be 8.62 mm. This consistency between the numerical simulations and the field measurements verifies the hypothesis. Finally, given the causes of underground confined water channels, corresponding technical measures such as piecewise secondary grouting are proposed to cut them off and avoid metro-segment leakage. The present research results contribute to the causes of and the laws governing the metro-segment leakage that occurs at subway stations and other reinforced structures.