Abstract: The authors investigate the interface temperature field during the freezing method used for the connecting channel of a super-large diameter shield tunnel. They also examine how the length of the non-circulating section of the freezing pipe affects the thickness of the frozen wall at the interface between the soil and segments. The research focuses on the freezing construction of the connecting channel for the super-large diameter shield tunnel on the East Sixth Ring Road of Beijing, employing both field measurements and numerical simulations to analyze both the temperature field and the thickness of the freezing wall at the soil-pipe segment interface. The results reveal the following: (1) The length of the non-circulating section in front of the freezing pipe significantly affects the freezing effect at the interface. As this length increases, the thickness of the freezing wall at the interface decreases. Under the working conditions of the Beijing East Sixth Ring Road, a non-circulating section length of 450 mm with a freezing pipe span of 1 m results in the inability to achieve a closed freezing wall within 56 d. (2) The thickness of the freezing wall at the interface and the maximum permissible length of the non-circulating section are greatly enhanced through the superposition freezing of a single-row of tube. Notably, a circular single-ring freezing configuration with an equivalent span yields similar results to that of single-row of tube freezing. (3) The thickness of the frozen wall at the interface significantly increases when the frozen interface is curved, compared to when the segment is flat. For a non-circulating segment length of 300 mm, the upper wall thickness increases by 15%, whereas the lower wall and sidewall each increase by 35%. This indicates that segment curvature is beneficial for freezing at the interface. (4) The interface between the frozen wall and tunnel segment represents a weak point in the frozen wall structure. During the freezing construction process, efforts should be made to minimize the length of the non-circulating section, and careful attention should be given to temperature fluctuations at the interface. Active thermal insulation measures should be implemented during freezing and excavation to prevent groundwater from penetrating the frozen wall, thereby avoiding potential water and sand gushing incidents due to defreezing at the interface during construction.

Key words: freezing method, super-large diameter shield tunnel, interface temperature field, connecting channel, numerical simulation