###### Abstract  
In order to prevent the problem of freezing pipe fracture in the process of artificial freezing construction, taking the main shaft freezing project of Shandong Yuncheng Mine as the background and based on the similarity theory, the similarity model test of freezing pipe in the composite stratum of the active freezing section is carried out. The test results show that the distribution of freezing temperature field in sand layer and clay layer is \"W\"-shape, and the temperature at the interface of outer ring pipe is slightly higher than that of the inner ring pipe. The change rate of freezing temperature can be divided into three stages: rapid decreasing section, slow decreasing section, and stable section. Compared with the clay layer, the sand layer has the shorter freezing closure time and the lower freezing average temperature. The frozen pipe is always in the state of vertical compression in the clay layer, while in the state of vertical compression first and then vertical tension in the sand layer. The maximum compressive strain in the clay layer is \(-305\)\(\mu\)c, which is equal to the vertical compressive stress of 64.1 MPa. The maximum tensile strain in the sand layer is \(406\)\(\mu\)c, which is equivalent to the tensile stress of 85.2 MPa. The bending direction of different freezing pipes is different in the different soil layers. The maximum bending strain of the frozen pipe in the clay layer is 779 \(\mu\)c, which is 2.6 times the vertical strain at the same location, corresponding to the bending stress of 163.4 MPa and reaching 0.69 times of the yield limit of frozen pipe, while the bending strain in the sand layer is very small. The vertical strain and bending strain of freezing pipes at the interface of soil layers are very small, but the bending strain is still dominant. artificial freezing; freezing pipe; composite strata; freezing temperature field; strain +
Footnote †: journal: Medical  
main shaft of Yuncheng Coal Mine, No.2 shaft of Zapoloz No.1 Coal Mine in the former Soviet Union, and No.L-1 shaft of Liubin Copper Mine in Poland [7]. Therefore, it is very necessary to study the stress and deformation law of freezing pipe under the complex geological conditions. According to the field investigation of frozen pipe fracture in China, 90% of the freezing pipe fracture positions are located in the clay layer or soil layer interface [8]. Since 1980, many scholars have carried out in-depth research on the fracture mechanism of freezing pipe in the deep clay layer by different research methods; see Table 1 for details. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Author** & **Published Time** & **Soil Texture** & **Research Stage** & **Research Method** & **Main Results** \\ \hline \multirow{4}{*}{[PERSON] [7]} & \multirow{4}{*}{1999} & Sand–clay & Active freezing & \multirow{4}{*}{Theoretical  analysis/  model test} & In the active freezing stage, the maximum  bending stress of the freezing pipe at the  soil interface can reach 80 MPa. In the  excavation stage, the stress of the freezing pipe is proportional to the displacement of the freezing wall. \\ \cline{1-1} \cline{3-5}  & & & Sand/clay/ & Excavation & \multirow{4}{*}{Model test} & The floor heave of the working face and  the advance displacement of the frozen  wall are the main reasons for the possible  pipe break below the excavation face. The  freezing pipe at the junction of the soil  layer will bear additional bending  moment and shear force, and it is easy to break the pipe. \\ \hline \multirow{4}{*}{[PERSON] [10]} & \multirow{4}{*}{2011} & Sand–clay & Active freezing  section & \multirow{4}{*}{Model test} & Due to the accumulation of strain energy  induced by bending, it is easy to cause the  freezing pipe to break during the  excavation stage.