Abstract: Water sealing by means of rapid liquid nitrogen freezing technology is proposed in the secondary watersealing of the working shaft of a tunnel. Conclusions drawn are as follows: 1) The lowest temperature measured in the monitoring hole is -30 ℃. 2) The data measured in C4 temperature monitoring hole show that the developing radius of the frozen wall is 0.54 m larger than that provided in the original design. 3) The data measured in C5 temperature monitoring hole show that the temperature of the soil 9.6 m below the ground surface is -10 ℃, and the freezing radius is larger than 0.70 m. 4) The effective thickness of the frozen wall at the crack is 0.85 m, the temperature inside the wall is -4 ℃, and the average freezing temperature at the connection joint drops as the depth increases.

Key words: Metro tunnel, working shaft, liquid nitrogen, freezing, frozen curtain, secondary freezing