Abstract: 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.

Key words: underwater shield docking, artificial freezing, frost heave effect, model test, similarity criterion, asynchronous freezing