Study on influence of freezing tubes layout on development law of temperature field of freezing wall

The coal mine vertical shaft sinking project in Huainan mining area is generally constructed by artificial freezing method. According to the analysis of many mine shaft freezing design schemes, the fewer number of frozen piping rings in the artificial freezing method, the smaller circle diameter, the smaller radius of the frozen front surface. For vertical wells such as wind shafts with a small net diameter of the wellbore, single-tube freezing design can meet design requirements. For the main and auxiliary wells with complex geological conditions and large net diameter and deep depth, single-tube design can no longer meet design requirements, the design scheme of the two-ring tube or even the three-ring tube must be used. The layout position of the freezing tube in the freezing design scheme is one of the factors related to the engineering cost and success or failure.In order to study the influence of different layouts of deep clay layer on the development of freezing wall temperature field, FLAC3D software was used to numerically simulate the influence of two-ring freezing tube and three-ring freezing tube on the development law of freezing wall temperature field,and simulation results of the three-loop tubes are compared with measured data.The research results show that compared with the frozen wall of two-ting tubes,the cooling effect of the frozen wall of the three-ring tube is better, the time of the circle is earlier, and the time of inner tube is 14～21 days earlier. The expansion speed of the frozen front is faster and shorter,the larger freezing wall thickness and lower freezing wall average temperature are formed. The average temperature of the frozen wall decreases approximately logarithmically with the extension of the freezing time. The effective thickness of the frozen wall is approximately logarithmic with the extension of the freezing time. As the relationship grows, the temperature field curve of the main interface develops in a V-shape in the freezing tube and gradually changes from saddle shape to trapezoidal distribution.The main interface temperature drops gradually with the extension of freezing time,the numerical simulation values of the three-ring tubes are in agreement with the measured values,the feasibility of numerical simulation is verified by comparative analysis.