Multifield coupled simulation study of seepage-induced disasters in high-pressure tunnels within rock formations of varying weathering degrees

Rock strata characteristics significantly influence tunnel seepage. A finite element seepage model was developed to analyze homogeneous seepage under varying rock strata and lining deterioration conditions. Numerical experiments with varied permeability coefficients investigated the relationship between seepage severity due to lining deterioration and rock strata properties. The model’s reliability was validated by comparing its seepage patterns with field data from Qingdao Jiaozhou Bay Tunnel. Results indicate: (1) Single homogeneous rock strata with varying properties exhibit similar seepage and stress distribution patterns. Seepage velocity is higher in the lower half of the tunnel lining, with maximum flow at the arch foot; flow within the lining is significantly lower than within the rock stratum. (2) Underwater tunnel seepage is closely correlated with rock strata characteristics. Higher rock permeability exacerbates lining deterioration and seepage. (3) Seepage patterns in composite strata align with those in single homogeneous strata. Seepage is most severe in moderately weathered zones with high permeability. Water flow tends to infiltrate tunnels along moderately weathered zones. This study provides theoretical and practical guidance for underwater tunnel seepage control.