高寒高海拔地区隧道工程中，大体积混凝土结构面临复杂热湿环境作用，早龄期热裂缝风险显著。基于典型高原铁路隧道，本研究构建现场监测与室内试验联合体系，系统揭示热裂缝的主控机制与关键影响因子。结果表明：温度收缩与结构约束耦合作用为裂缝形成主导机制，入模温度与环境温度具有显著诱发效应，而干燥收缩作用相对次要。进一步，提出集材料调控（抗裂剂控温）、工艺干预（喷淋降温）及结构优化（梯度掺加弹模调节）于一体的多维控裂技术体系。工程实测数据表明，材料温控措施可将混凝土温升值控制在18~22?℃、峰值温度降至40?℃以下，热峰出现延迟5~10小时；辅助喷淋技术在低温区段可再降低峰值6~7?℃；梯度掺加策略构建“刚上软下”弹模梯度结构，有效缓解高应力区域应力集中。试验段总裂缝发生率控制在5.9%，验证了三维协同控裂路径在高寒复杂环境下的适应性与工程可行性。

In cold and high-altitude tunnel projects, mass concrete structures are vulnerable to early-age thermal cracking due to intensified internal temperature gradients and external environmental constraints. This study investigates the thermal cracking mechanism and develops a multidimensional control strategy by integrating field monitoring and laboratory testing in a representative plateau railway tunnel. Results show that thermal shrinkage, coupled with structural restraint, is the dominant cause of cracking, while drying shrinkage plays a secondary role. Key external factors, including casting and ambient temperatures, significantly influence crack formation. A comprehensive control system—comprising chemical temperature regulation using crack-resistant admixtures, physical surface cooling via template water spraying, and elastic modulus gradient design through admixture distribution—is proposed. Field results demonstrate that the temperature rise can be constrained within 18~22?℃, peak temperatures suppressed below 40?℃, and thermal peaks delayed by 5~10?hours. Additional spraying reduces surface temperatures by 6~7?℃ in cold segments. The modulus gradient strategy constructs a “soft-base, stiff-top” structural profile that effectively mitigates stress concentration in constrained regions. The proposed system reduced the cracking rate to 5.9%, confirming its adaptability and engineering applicability in thermally vulnerable tunnel structures under extreme climatic conditions.

TU528

中国建材集团关键技术攻关“揭榜挂帅”项目（编号：2023SJYL04）；国家重点研发计划项目(编号：2023YFB3711400)