Safety assessment of shield tunnels with initially mechanically damaged concrete in water‐rich strata

Abstract Current understanding about how initial mechanical damage in concrete affects shield tunnel safety in water‐rich strata remains inconclusive. To address this issue, triaxial stress‐seepage tests are introduced to investigate the mechanical parameters of concrete with initial mechanical damages. An engineering‐scale numerical model is established to evaluate the coupled effect of initial mechanical damage and water‐rich strata on tunnel safety. Furthermore, parameter analysis is conducted considering the coupled effects of initial mechanical damage, concrete time‐dependent deterioration and steel corrosion. The findings reveal that initial mechanical damage can reduce concrete strength by up to 16.5% under non‐seepage conditions and 21.1% under 1 MPa seepage pressure. For conventional design schemes, shield tunnels remain uncompromised under the specified unfavorable loading case despite the presence of both initially mechanically damaged concrete and a water‐rich environment, provided that initial damage does not induce concrete cracking. However, when initial mechanical damage interacts with concrete deterioration and steel corrosion, tunnels become susceptible to cracking, significantly compromising service safety. Further research may prioritize the combined effects of initial mechanical damage with time‐dependent factors to better evaluate the long‐term service safety of shield tunnels.