富水砂层盾构液氮冻结温度场实测研究OA

Based on the liquid nitrogen freezing opening project for shield chamber opening of a large-diameter slurry shield in the Eastern Guangdong Intercity Railway,this study addresses the unclear evolution of the temperature field during liquid nitrogen freezing and the lack of quantitative evidence regarding groundwater interference of the project in water-rich sand layers.A field monitoring system consisting of 48 freezing holes and 5 temperature-mea-suring holes was installed to obtain full-cycle temperature field data.Field measurements were conducted to analyze the development of the frozen curtain,identify the freezing blind zone,and investigate its causes.The results showed that liquid nitrogen freezing is feasible.The slowest freezing development speed reached 111 mm/d,and the frozen curtain thickness attained 1.8～2.2 m;Groundwater flow was the key factor causing local freezing lag;After sealing the pumping wells,the cooling rate increased by 39％.The conventional single-row hole layout poses a risk of non-uniform freezing.Therefore,a combination of double-row hole arrangement with a liquid-nitrogen-CO2 hy-brid refrigeration mode was recommended.Pre-freezing environmental control was also enhanced,improving both the safety and economy of the project.