Research On Designing And Calculating Methods Of Artificial Freezing Curtain For The Project Of Connecting Metro Passage-ways

Artificial freezing method was first applied in mine shaft engineering in the19thcentury which developed into the main method of deep vertical shaft construction. Inrecent years, with the rapid development of the underground railway construction,artificial freezing method has been a mutual reinforcement method of Metroconnected passage-way construction in soft soil area. The design of previous artificialfreezing curtain is primarily built on the basis of the construction of the mine shaftengineering, while there are significant differences in depth, methods and stress statebetween the construction of the urban underground and the mine shaft engineering. Sowe need to study the unnatural freezing method in underground engineering.At present, the required strength, deformation and thermal physical parameters ofTianjin subway level liaison channel design are used artificially frozen index under-10of Shanghai. There is a big difference between Tianjin soil and Shanghai soil, sothe use of Shanghai index to artificial freezing of the Tianjin curtain design isunscientific. This paper is based on the soil in Tianjin to conduct research, selectingrepresentative areas of soil, according to the "Coal permafrost test specifications ",o nthe undisturbed soil in Tianjin to conduct-10℃strength, thermal physics experiment,obtained the physical and mechanical properties of Tianjin artificial freeze soil,applied to Tianjin artificial freezing curtain designs.Subway level liaison channel design includes artificial freezing freeze curtain wallthickness and freezing time design. Through-10artificially frozen physical andmechanical testing to determine permafrost strength, disinformation and thermalphysical pentameters, according to the intensity of the control method, considercertain safety cofactor, calculated freeze wall thievishness. When freeze wallthickness is determined, for checking whether frozen pipe deformation within theallowable range, the maximum deformation need checking frozen wall meets thestationary pipe deflection requirements. Frozen wall strength, deformation meet therequirements, it is necessary to freeze pipes arranged in a precise calculation requiredunder the freeze time. Freeze time includes freezing wall post laps time andenthusiasm to freeze time. Frozen wall post lap time is measured from the groundfreezing begins, with the continuous release of frozen pipes out cold, freezing pipessurrounding soil is frozen, freeze cylindrical form, with the continuation of deepcold, freezing cylinder radius increasing until the formation of the adjacent pipe freeze freezing cylinder intersection of the time. Actively freezing period is measuredfrom the beginning to the formation of ground freezing design requirements needed tofreeze the average temperature of the ice wall thickness and the time required.Calculations assume freezing time calculation time freezing temperature field issteady temperature field would be frozen pipe into the surrounding soil freezing zoneand cooling zone, according to the principle of conservation of energy-that is therelease of frozen pipes freezing cold curtain absorption equal amount of cold,calculating freezing time.Finally, according to the Tianjin artificially frozen soil physical and mechanicalproperties, gave the Tianjin Metro Line3Station fixings Zhangxingzhuang levelliaison channel between stations for artificial freezing curtain design.