Research On The Temperature Field Of Liquid Nitrogen-Bring-Combined Freezing Methord In Inclined Shaft

Inclined Shaft is widely used in projects in western districts of China.Brine freezing method is usually adopted to pass through the upper unsteady strata.Brine freezing method takes lots of time and is very slow.If liquid nitrogen combining brine freezing method is considered,time will be saved and many kinds of problems during the construction can be easily dealt with.So a liquid nitrogen-brine-combined breezing method is proposed here,which has already been applied to some inclined shaft constructions but is still lack of a thorough and systematic research.Therefore,three freezing methods by different kinds of combination of brine and liquid nitrogen are introduced in this article which can be described seperatedly as “liquid nitrogen after brine freezing”, “brine after liquid nitrogen freezing”and“liquid nitrogen combining brine freezing”.And the change law of the freezing temperature fields are also discussed here.Firstly,analytic analysis of temperature field of combined freezing is figured out.The formula of single pipe freezing of liquid nitrogen is obtained by revising that of brine,and from which formulas of single pipe freezingby liquid nitrogen after brine freezing method and brine after liquid nitrogen freezing method as well as that of douple pipe freezing by liquid nitrogen combining brine freezing method are derived.Secondly,numerical simulation research on temperature field of combined freezing method has been carried out.Plane conduction calculation model was established,large scale computation software package was used,freezing temperature field on single,double and multirow of freezing pipes were calculated successively,the influence laws of parameters like freezing pipe layout space,soil thermal conductivity,moisturecontent,freezing time of brine,brine temperature,freezing time of liquid nitrogen,liquid nitrogen temperature on temperature field was obtained and the interaction law of adjacent row of freezing pipes on temperature field by different freezing method was mastered.A 3D thermal model was created by parameters inversion to study temperature field due to nonumiform temperature distribution of liquid nitrogen.And law of the temperature distribution was obtained.Finally,based on the measured on-site statistics like original ground temperature,brinetemperature,temperature of thermometer hole and nitrogen aerofluxus of the third and fourth freezing sections of Yuandatan auxiliary inclined shaft, the change law of the combined freezing temperature fieldwas obtained.