Table 7 Initial freezing time of the surrounding rock in the airbag and airbag-less models.

From: Frost protection mechanism based on rubber airbag interlayered composite lining system for cold-region tunnels

Model

Without

With

Initial freezing time (h)

16.2

52.0

  1. The freezing of the surrounding rock is marked by the appearance of 0 °C at the base point on the outer surface of the secondary lining/rubber airbag structural layer. The initial freezing time refers to the time interval between the appearance of 0 °C at the base point and the start of the freezing test.
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