Research and Application of Shield Opening Technology Based on Freezing Method
Currently,the common methods of shield opening are ground pre-reinforcement atmospheric pressure opening,air pressure opening,atmospheric pressure cutter opening,etc.,as well as salt water freezing cutter opening at atmospheric pressure.Shield opening and tool changing should ensure both the stability of the working face and the safety of workers,and reduce the impact on the surrounding environment on the premise of meeting the requirements of the construction period.Therefore,the study of shield opening technology is of great necessity.Based on the existing common methods of shield opening and tool changing in China,the opening technology of rock and soil around the cutter head reinforced by liquid nitrogen and salt water combined freezing was studied.The construction process and technical points of liquid nitrogen and salt water combined freezing in super-deep buried water-rich composite strata were introduced.The research contents include freezing wall design,the mud film production process,the slurry gas replacement process,etc.And also based on engineering examples,the contents of the decompression test,opening and tool changing,forced thawing and construction monitoring were analyzed.It is concluded that the timing of slurry gas replacement can be comprehensively determined according to the medium temperature in the slurry silo,the pressure in the slurry silo,and the decompression test.
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