Model test study on the formation of basin-shaped freezing range in sandy gravel stratum under seepage conditions

The basin-shaped freezing method has a wide range of engineering application prospects because it is environmentally friendly and not sensitive to the depth of the phreatic layer. Based on the similarity theory, multiple sets of model tests were performed to study the development of the basin-shaped freezing range and analyse the influence of seepage velocity, the distance between the freeze pipes and the refrigerant temperature. The test results revealed that, under the influence of group pipe effect, the cooling rate in the middle of the basin bottom was the fastest, and the formation time was the shortest. A single factor had no noticeable impact on the formation time of the closed basin bottom. However, the formation speed of the top surface of basin wall was the slowest under the influence of boundary effect and was significantly influenced by various factors. When the basin wall freeze pipes were arranged with the same spacing along and perpendicular to the water flow direction, the formation time of the top surface of the basin wall perpendicular to the water flow direction was the longest. When the spacing of the freeze pipes along the water flow direction was greater than that perpendicular to the water flow direction, attention should be given to the temperature of the top surface of the basin wall in both directions. The empirical relationships between the formation time of the basin wall and the distance between freeze pipes and the seepage velocity were obtained through regression analysis.