Study On The Change Rule Of Temperature Gradient In The Frozen Wall Under The Condition Of Double Ring Freezing Hole

With the development of city and the progress of science and technology,artificial freezing method is widely used in mine roadway and urban underground engineering.Scholars at home and abroad have carried out a lot of research on the distribution and variation law of freezing temperature field,and achieved rich results.At present,the research on the freezing temperature field mainly focuses on the thickness and average temperature of the freezing wall,but the research on the temperature gradient in the freezing wall which leads to the temperature distribution and changes is insufficient.Based on existing research findings,this thesis uses the finite element numerical simulation analysis method,combined with the field measured data of a cross river tunnel freezing project in Shanghai,comprehensively analyzes and compares the development law of the freezing temperature field related indicators obtained from the finite element numerical simulation and the field measurement,and takes the other freezing temperature field index data and research results as an example in this thesis.We focus on the distribution and variation of temperature gradient in the freezing wall with time and space,comprehensively analyze the relationship between temperature gradient and other indicators,explore the deeper law of freezing temperature field,and establish a new evaluation and analysis system of freezing temperature field with temperature gradient,so as to promote the transformation of evaluation mode of freezing temperature field from temperature to temperature gradient.The main research contents and methods are as follows:(1)The typical parameter test,single factor test and orthogonal test are carried out by using the numerical model to study the temperature distribution law in the freezing process and characteristic surface.Based on the temperature data,the distribution and variation law of temperature gradient in each region of the frozen wall with respect to time and space are further studied.The influence degree and significance of brine temperature,water content,inner and outer freezing pipe spacing,inner and outer freezing pipe spacing on temperature gradient were studied,and the evolution law of freezing wall temperature gradient was obtained;(2)Based on the field measured data,the temperature change and the development state of the frozen wall are analyzed,and then the variation law of the temperature gradient in each area of the frozen wall with respect to time and space during the freezing process is studied,and the relationship between the temperature gradient in the frozen wall and the basic index of the temperature field is obtained;(3)The accuracy of the analysis and the feasibility of numerical calculation are verified by comparing the results of numerical simulation and engineering measurement,and the evolution law of temperature field under the condition of double circle hole arrangement is obtained.The research content of this thesis can provide a certain reference value for the future study of temperature gradient of freezing temperature field and the actual freezing engineering.There are 69 figures,22 tables and 73 references in this thesis.