Abstract: Artificial ground freezing technology has the advantages of reliable water sealing, low environmental impact and strong applicability. It is one of the effective methods for underground excavation in urban subway to achieve the waterless construction. The cooling power is continuously depleted by groundwater flow, resulting in the delay of closure of frozen wall and the thickness less than expected. A physical model test with groundwater seepage velocities of 0, 5, 10 and 15 m/d was conducted based on the freezing project of a subway cross passage in Beijing Subway Line. The influence of groundwater seepage velocities on the formation of frozen wall was investigated, and the variation of cooling power in the freezing process was discussed. The results show that under seepage condition, the bottom and top plates of the cross passage intersect first, followed by the downstream sidewall, and finally the upstream sidewall, which is the weak part. At the groundwater seepage velocities of 0, 5 and 10 m/d, the closure times of the frozen wall are 60, 114 and 444 minites, respectively, while it is impossible to form continuous frozen bodies at 15 m/d. The cooling power increases with the groundwater seepage velocities. The energy consumption at the groundwater seepage velocities of 5, 10 and 15 m/d increases by 67.0%, 88.5% and 120.1%, respectively compared with no-seepage condition. The results can provide a basis for the design and construction of cross passage freezing under seepage conditions.

Key words: cross passage, artificial ground freezing, groundwater seepage velocity, model test, frozen wall