Moisture migration within the melting laps during construction controls frost heaving damage of lining in permafrost tunnels

Frost heaving damage is a typical hazard in tunnels constructed in cold regions, among which frost heave induced by the freezing expansion of surrounding rock stands as one of the primary factors leading to stress concentration and even cracking failure in lining structures. Under the influence of construction thermal disturbances, the thawing of surrounding rock is accompanied by moisture redistribution, where the characteristics of water distribution play a critical role in governing frost heave. This study establishes a thermal-hydro-mechanical (THM) coupled model for melting laps, validated through the Jiangluling Tunnel case. Integrating laboratory freezing tests on gravel soils with numerical simulations, we investigate moisture migration impacts on lining frost heaving damage under construction thermal disturbance and operational refreezing. The results indicate: (1) The numerical simulations align closely with field monitoring data, validating the accuracy of the model for this project. (2) Pore ice formation without moisture migration generates negligible frost heave pressure. (3) Moisture redistribution during construction creates water-enriched zones at tunnel flanks, causing tensile stress concentration (peak 6.008 MPa) at lining sidewalls. (4) The tensile stress at the inner walls of the lining initially increases gradually, then rises rapidly, and finally stabilizes. Mechanistic analysis reveals that moisture redistribution within the melting laps under construction thermal disturbance establishes essential material precondition for frost heave. During operational phases, initial frost heave develops in surrounding rocks, which subsequently subjected to seasonal freeze–thaw cycles triggers cumulative frost heave effects. Consequently, maximum tensile stress in lining structures demonstrates progressive annual escalation. This research provides theoretical basis for frost-resistant lining design in permafrost tunnels.