Influence factors and formation properties of temperature field in the frozen wall of double ring pipes

In order to research the change law of the temperature field of the frozen wall of double-circle pipes, an auxiliary shaft in Huainan coalmine was taken as the research object, the FLAC^3D software was used to numerically simulate the formation process of the temperature field of the frozen wall of double-circle pipes and the influence of different factors on average temperature of frozen wall based on the relevant geological parameters. The research results show that temperature of the soil in the double-circle pipes is the lowest, and temperature on both sides increases gradually, the interval between frozen holes is smaller, the time of circulation is earlier, and the closed unfrozen pressurized water tank is formed after the inner and outer ring pipes are in contact, which is unfavorable to the frozen wall, the frozen front face in the inner side expands faster than that in the outer side; average temperature of frozen wall of double-circle pipes decreases with freezing time in a logarithmic relationship, the effective thickness increases obviously after the intersection of the inner and outer rings, and increases approximately logarithmically with freezing time; temperature field curve of main and interface of double-circle pipes changes gradually from saddle-horse shape to trapezoidal distribution with freezing time, interface temperature field expansion speed is greater than main surface temperature field; the initial temperature, brine temperature and thermal conductivity of the soil have a great influence on the average temperature of frozen wall, the lower initial temperature and brine temperature, the higher the thermal conductivity is, the lower the average temperature of frozen wall is. The research results provide reference for the design and construction of the related freezing project.