Study On Freezing Temperature Field Composed With Thin Freezing Wall By Combined Tube In The Large Diameter Foundation Pit

China is developing rapidly since stepping into the 21 st century,therefore,it has generated a great number of deep foundation pit engineering,which had led the project design theory and construction method to a severer circumstance at the same time.To be more specific,as the continual growth in foundation pit’s diameter and depth,the multi-circle freezing method would be applied to make the thicker freezing wall,which would give rise to the resource wasting.Therefore,the studying of the developing law and characteristics of freezing temperate field with multiple circles of thin freezing pipes seems to be considerable significance in the current circumstance.In this paper,experimental and digital simulation approaches have been applied in researching and analyzing.Firstly,Cosmol has been utilized to establish numerical model,conducting the research of the development law for freezing temperature filed which is constituted by three-circles freezing pipes under the typical parameters,and the calculation of average temperature as well.Moreover,the paper is designed to demonstrate the influences of various factors like,moisture content,freezing tube’s hole spacing,tube’s outside diameter,temperatures of saline solution and the number of frozen tubes would bring on the freezing temperature filed in a single factor experimental way,explore the degrees of influence of factors would carry to the freezing temperature field corresponding to different freezing time manner.As the result,32 orthogonal experiments were conducted to demonstrate the remarkable impact of corresponding factors on the freezing temperature field.Furthermore,by deriving the similarity criterion and conducting physical simulation experiments in large diameter deep foundation excavation,we had concluded the development law of freezing temperature filed within three circles of the frozen thin wall.And the independent variables like frozen wall thickness and the curves of average temperature changed over time have been fitted mathematically,to get the fitting equation as the result,and the derivative of this equation was performed to demonstrate the velocity equation of freezing wall thickness and average temperature.Experiment data is collected and analysed to draw the conclusion.The researches initiated in this paper would perform a guiding and reference role in both the design approach and construction for large-diameter deep foundation pit with multi-circle freezing in the future.There are 58 figures and 25 tables as well as 70 references in the paper.