盾构水下对接开挖施工中采用冻结加固是确保施工安全的关键措施，但由此引发的冻胀效应对盾体受力及结构变形产生不利影响。为明确非对称式异步冻结对冻胀效应的抑制机理，基于某富水软土地层大直径盾构对接工程，开展几何相似比为1∶20的物理模型试验，系统研究同步与异步2种不同冻结控制模式下的地层温度发展、冻结壁形成及冻胀力演化规律，揭示异步冻结条件下冻胀效应的时空分布特征。试验结果表明： 1）在异步冻结模式下，冻结壁约89 d达到工程原型设计厚度3.9 m，相较于同步冻结延长约21 d； 但通过分阶段冷量输入，可加快冻结壁发展速率、缩短交圈时间。2）同步冻结过程中，盾壳表面所受最大冻胀力为地层初始压力的2.01倍，相比之下异步冻结通过后行盾构侧开敞系统有效释放冻胀力，使盾壳表面最大冻胀力降至地层初始压力的1.57倍，其减小量为地层初始压力的44%，同时先行盾构侧、后行盾构侧及对接处的冻胀力均得到显著抑制，表明异步冻结具有良好的冻胀控制效果。3）“先行盾构侧主冻结+后行盾构侧补强”的非对称式异步冻结方案，可在满足冻结设计要求的基础上有效抑制冻胀作用，提高盾构对接过程中结构安全性与施工适应性。
Artificial ground freezing is an important process for ensuring construction safety during underwater shield docking; however, the resulting frost heave effect adversely affects the stress state and structural deformation of the shield shell. To clarify the suppression mechanism of frost heave under an asymmetric, asynchronous freezing condition, a physical scale model with a geometric similarity ratio of 1:20 is constructed based on a large-diameter shield docking project in a water-rich soft soil stratum. This study systematically investigates the development of soil temperature, the formation of frozen walls, and the evolution of frost heave forces under synchronous and asynchronous freezing modes, revealing the spatiotemporal distribution characteristics of frost heave under asynchronous freezing conditions. Under asynchronous freezing, the frozen wall reaches the prototype design thickness of 3.9 m after approximately 89 days, which is approximately 21 days longer than the time required under synchronous freezing, but staged cooling input accelerates the rate of frozen wall formation and shortens the closure time. In addition, during simultaneous freezing, the maximum frost heaving force acting on the shield shell reached 2.01 times the initial ground pressure. By comparison, the asynchronous freezing scheme, incorporating an open system on the trailing shield side, effectively relieved frost heaving, reducing the maximum frost heaving force acting on the shield shell to 1.57 times the initial ground pressure, corresponding to a reduction of 44% of the initial ground pressure. In addition, the frost heaving forces on the leading shield side, trailing shield side, and at the docking interface were all significantly reduced, indicating that the asynchronous freezing scheme offers superior frost heave mitigation performance. Furthermore, the asymmetric asynchronous freezing scheme involves dominant freezing on the leading shield side and supplementary freezing on the trailing shield side, which effectively suppresses frost heave while satisfying the design freezing requirements, thereby improving structural safety and adaptability during the shield docking process.
