Abstract: The complex geological conditions of rich gas and dynamic water in the Qiantang river considerably affect the evolution and distribution characteristics of the temperature field during the freezing process of the connecting gallery. A case study is conducted on the in-situ monitoring of a freezing project at the connecting gallery of the Hangzhou metro line 6 in the Qiantang river. The process of formation temperature variation at different positions during the freezing process is investigated, and the temperature variation characteristics of the freezing pipe after freezing are analyzed to determine the influence of gas and groundwater flow on the freezing-temperature field of the connecting gallery. The main results are summarized as follows. (1) Under bilateral hole distribution, the average speed of frozen soil inward development is 1.47 times that of outward development. When the freezing is stopped for 6 h, the temperature in the outer and inner tubes increase by 5 ℃ and 10 ℃, respectively. (2) The presence of bubbles hinders the cold transfer process of the freezing tube to the surrounding soil, thereby significantly affecting the freezing effect. The formation temperature at which bubbles exist during the freezing process is 8–18.4 ℃ higher than that at end position of freezing tube. (3) Groundwater flow also affects the distribution of cooling capacity in the formation. After a frozen period of 57 d, the temperature difference between the upper and downstream positions in the freezing tube reaches 8 ℃. When the freezing is stopped for 6 h, the temperature in the freezing tube at the corresponding position increased by 5 ℃ and 2 ℃, respectively. The results show that the bilateral divergently-arranged freezing tubes in tunnel can effectively mitigate the influence of gas and dynamic water on the formation of the freezing of the connecting gallery. Additionally, the bubbles in the formation and the flow of groundwater affect the distribution characteristics of the freezing-temperature field.

Key words: artificial freezing method, gas- , and water-bearing strata, metro connecting gallery, double-side divergently-arranged freezing pipes, freezing-temperature field, field test