Abstract: Ground sealing poses challenge to shield tunneling when replacing tail brush. To address this challenge and guarantee safe construction, a cavity-type freezing steel segment technology is developed. Numerical simulation and field measurement are utilized to systematically investigate the evolution and propagation patterns of the frozen wall temperature field as well as its stress mechanism, clarifying its mechanical response characteristics and strength weakening patterns, thus providing optimization suggestions for corresponding construction technology. The research results show that: (1) The cavity-type freezing steel segment forms a freezing wall in a faster, more efficient, and more uniform manner. (2) The frozen wall formed by cavity-type freezing steel segments is not applicable to freezing wall design based on the semi-infinite body assumption for shaft structures. Numerical simulation and calculation analysis are carried out combined with practical engineering. The large refrigeration surface of the cavity-type freezing steel segment completes refrigeration rapidly in the early stage and promotes the development of the freezing wall. The stress distribution characteristics in the model calculation results differ significantly from those of shaft structures in traditional freezing design. (3) In view of the strength weakening characteristics of the frozen wall formed by cavity-type freezing steel segments, the construction scheme is optimized based on the erosion characteristics of external heat on the freezing wall and its stress mechanism during construction. The tail brush replacement principle of “demolishing and installing block by block and timely thermal insulating” is proposed and verified in practical engineering.

Key words: cavity-type freezing segment, artificial ground freezing, temperature field, stress mechanism, numerical simulation