为降低预制沉管隧道管节大体积混凝土的早期开裂风险，建立集成水化、温度、湿度与应力场的高保真多场耦合数值模型，以明珠湾隧道工程为背景，系统模拟了混凝土早期温度、应力及开裂风险的演变过程。通过数值模拟对比分析基准、持续冷却、集中冷却及后浇带4种工况下的混凝土开裂风险系数。结果表明： 1）水化热引起的显著温度梯度与外部超高约束的共同作用是导致开裂的主要原因，底板与顶板表面为最易开裂区域； 2）通过“降低放热峰值”冷却措施将核心区最高温升控制在54 ℃左右，并使开裂风险系数降至0.7以下，其中2 d集中冷却与30 d持续冷却效果相当，更具经济性； 3)后浇带区域呈现“低温升、强约束”的受力状态，采用普通混凝土时约束效应取代温升成为开裂主导因素。工程实践表明，基于模型提出的“早期集中冷却+分段浇筑”协同控制策略，可成功将混凝土核心温度控制在55 ℃以下，实现管节主体及后浇带接合部位无有害裂缝。

To mitigate the early-age cracking risk in mass concrete of precast immersed tunnel elements, a high-fidelity multi-field coupling numerical model integrating hydration, temperature, humidity, and stress fields is established, systematically revealing the cracking mechanism and evaluating the effectiveness of prevention measures. Taking the Mingzhu Bay Tunnel project as a case study, the evolution of early-age temperature, stress, and cracking risk in concrete is systematically simulated. The concrete temperature, stress, and cracking risk coefficient are quantitatively compared under four working conditions (i.e., baseline, continuous cooling, concentrated cooling, and postcast section). The results indicate that: (1) The combined effect of significant temperature gradients induced by hydration heat and external ultra-high constraints is the primary cause of cracking, with the surfaces of the base slab and roof slab identified as the most vulnerable areas. (2) Cooling measures function to “reduce the peak heat release”, controlling the maximum temperature rise in the core region to about 54 ℃ and reducing the cracking risk coefficient below 0.7. Notably, a 2-day concentrated cooling period shows equivalent effectiveness to 30-day continuous cooling, offering greater economic feasibility. (3) The post-cast strip exhibits a special mechanical state characterized by “low temperature rise and high constraint”, where constraint effects, rather than temperature rise, dominate the cracking risk when ordinary concrete is used. Engineering practice verifies that the coordinated control strategy of “early-stage concentrated cooling + segmented casting” proposed based on the model can successfully maintain the core concrete temperature below 55 ℃, achieving crack-free conditions in both the main tunnel element and the postcast section joint.