A new cryogenic sealing process for the launch and reception of a tunnel shield

Abstract

Abstract The success of a shield’s launch and reception processes for tunnels in sandy grounds with high water tables depends heavily on the ground improvement of the soils within the portal zone. To achieve this, a sealing process based on the cryogenic freezing principle is herein proposed. This process involves using liquid nitrogen as the working fluid to create a cryogenic environment, through which passing underground water would be frozen to create a seal. To confirm the feasibility of this method, full-scale experimental field tests were conducted, which include the design of the experimental device, the experimental process, and preparation of the experimental mud sample. The experimental results indicate that a thermal additive could accelerate the freezing speed, and the frozen device had a good sealing capacity when the hydraulic pressure was over 0.15\u202fMPa. Additional information on the implementation of the feasibility test was also reported.