Abstract: Difference in groundwater salinity can impact the thermodynamic properties of soil. Understanding the influence of groundwater salinity on the freezing temperature field at the bottom of foundation pit under seepage condition is crucial for municipal underground engineering, mine engineering, and undersea tunnel construction. In this study, we employed the COMSOL hydrothermal coupling module to investigate the development pattern of the freezing temperature field at the bottom of a foundation pit with varying salinity of groundwater. Through thickness comparison and path analysis of the freezing wall, we determined the effect of groundwater salinity on freezing temperature field: when salinity exceeds 3%, seepage flow significantly affects the formation of the freezing curtain at the pit's bottom, and in particular, the downstream is more affected than the upstream. Furthermore, an increase in salinity leads to a gradual rise in the freezing curtain's temperature after an initial freezing period of 40 days. This increase in salinity is also accompanied by slower cooling rate, thinner freezing curtain, and consequently, poorer freezing effects.

Key words: freezing of foundation pit bottom, hydrothermal coupling, seepage field, salt content, numerical simulation