Early-Age Cracking Behavior and Prevention Strategies of Hydraulic Tunnel Lining Concrete Under Varying Curing Regimes

Early-age cracking of tunnel lining concrete under adverse curing threatens long-term durability. This study integrates material-scale testing, structural-scale testing, and multiscale simulation to investigate cracking behavior and prevention strategies. Material-scale experiments on self-compacting concrete (SCC) under three curing regimes and four demolding times (1–7 d) revealed that extending demolding time mitigated strength loss, with 28 d strength increasing by up to 22.3% under low-temperature curing. The DuCOM model predicted strength evolution with an average 28 d error of 2.5%. Structural-scale tests under laboratory ambient exposure (S1) and moisture-retaining curing (S2) showed that S1 specimens cracked at ~8 d when the stress-to-strength ratio exceeded 1.0, whereas S2 specimens remained crack-free. The coupled DuCOM–COM3D framework captured internal stress evolution with peak stress errors within 1.77% (S1) and 8.74% (S2). Based on the stress-to-strength ratio criterion as a preliminary indicator, three prevention measures are proposed: extending demolding time, immediate moisture-retaining curing, and real-time early warning. This quantitative framework provides a preliminary basis for early-age cracking risk assessment in the present experimental configuration.