Monitoring And Analysis Of Temperature Field Distribution Characteristics Of Artificial Freezing In Subway Cross Passage

In the process of subway construction,it is often faced with complex construction environments such as weak strata,shallow buried tunnel and groundwater seepage.At present,the commonly used shield construction method can often effectively overcome the above difficulties.However,due to the narrow working environment,it is difficult to use large-scale mechanical construction in the connection channel project of shield tunnel,resulting in the generally high risk level of the connection channel.The traditional cement system improvement method is difficult to solve similar problems.Therefore,the artificial freezing method has become the preferred method for the construction of the connection channel.Based on the analysis of artificial freezing cases at home and abroad,this paper takes the horizontal freezing of the contact channel between Lintou Station and Nanyong Station of the first phase project of Guangzhou Rail Transit Line 7 as the engineering background.Through field test and analysis,combined with numerical calculation method,the temperature field distribution characteristics and development law of the contact channel and pump room under the condition of rich water and soft soil are studied.The main research conclusions and innovations are as follows :(1)Through the observation of brine de-loop temperature,pressure relief hole pressure and temperature measurement hole data,the freezing process of contact channel can be roughly divided into : rapid decline stage,slow decline stage,temperature stability stage and maintenance freezing stage.With the extension of freezing time,the expansion of soil freezing wall gradually slows down,and the freezing wall gradually forms.(2)Using field measurement and interpolation method to determine the temperature distribution of segment-soil interface can effectively improve the accuracy of numerical calculation of contact channel temperature field.The results show that the freezing wall of the contact channel near the tunnel area is significantly weaker than that in the middle area of the contact channel.(3)Based on the numerical calculation model,a general contact channel temperature field calculation software is developed,which simplifies the complex finite element calculation process and makes it a new tool and method for front-line engineering and technical personnel to analyze the freezing effect and judge the risk.