Abstract: In coastal saturated silt sand strata, the freezing effect of the connecting gallery is significantly affected by the interaction between seepage and salinity. To address this problem, a threedimensional thermohydromechanical multifield coupling method under the interaction of seepage and salinity is proposed based on a case study regarding the #4 connecting gallery between the Yongxing Avenue Station and Shennan Road Station of Nantong metro line 1 constructed using artificial freezing method. First, insitu monitoring results are analyzed. Then, a threedimensional numerical analysis model is established. Finally, the commercial software COMSOL Multiphysics is used to simulate the freezing process of saturated silt sand strata. The outcomes of the study show that: (1) The numerical simulation results are in good agreement with the field monitoring data and the established numerical calculation model is highly reliable. (2) The combined effects of seepage and salinity will delay the artificial freezing time, and the maximum delayed time is 7.52 days. (3) The difference in waterhead causes an asymmetrical frozen wall. Hence, the upstream freezing temperature drops very slowly, resulting in a thinner frozen wall and a thicker downstream frozen wall. (4) Furthermore, the salinity can only slow down the cooling rate of the artificial freezing method.

Key words: metro connecting gallery, freezing method, saturated silt sand strata, thermohydromechanical multifield coupling, numerical simulation