## 5 Conclusions and Future Prospects  
Addressing the influence of the brine cooling plan on the construction process of the freezing method, this study was based on the background of the construction of a contact channel and pump room in the interval between Gongzhongfu Station and Inner Mongolia Stadium Station by the Hohhot City Railway Line 2 Phase I Project using the freezing method. Subsequently, the numerical model pair of the stratum-freezing tube was established, and the temperature field distribution of the contact channel control section under different brine cooling plans and soil freezing wall morphology was analyzed and compared with the actual measured temperatures. The measured data and the cooling curve obtained from the numerical calculation of the cooling law were basically consistent, and the values were relatively close. This indicates that the numerical calculation method based on the 3D finite element model can simulate field results more accurately. At the early stage of freezing, the discrepancy between the numerical calculation results and the measured data in the field was relatively small, and a deviation gradually appeared with an increase in time. The conclusions of the study can be drawn as follows:  
1. The measured average rate of temperature drop in the C5 temperature measurement hole was about 0. 67 \({}^{\circ}\)C/d, with a very high difference of 20.7 \({}^{\circ}\)C. The numerical simulation results were about 0.57 \({}^{\circ}\)C/d, with a very high difference of 20.1 \({}^{\circ}\)C. After 40 d of active freezing, the measured temperature in the C5 temperature measurement hole was \(-8.1\)\({}^{\circ}\)C, and the numerical simulation temperature was \(-7.3\)\({}^{\circ}\)C.
2. The measured average cooling rate of the C7 temperature measurement hole was about 0. 852 \({}^{\circ}\)C/d, and the extreme difference was 21.3 \({}^{\circ}\)C; the numerical simulation result was about 0.908 \({}^{\circ}\)C/d, and the extreme difference was 22.7 \({}^{\circ}\)C. After 40 d of active freezing, the measured temperature of the C7 temperature measurement hole was \(-5.2\)\({}^{\circ}\)C, and the numerical simulation temperature was \(-6.2\)\({}^{\circ}\)C.
3. The trend of the numerically simulated temperature and the temperature obtained from the actual measurement was essentially the same at the same location of the temperature measurement point. As the numerical calculation did not take into account the influence of groundwater, there can be a situation where the numerically simulated temperature is slightly lower than the actual measured temperature. This means that in the actual project, the heat exchange in the permafrost curtain is more complicated due to the presence of groundwater, which also shares part of the cooling. Thus, the measured temperature is slightly lower than the numerical simulation because there is a certain error between the physical parameters and boundary conditions obtained from the test and the actual project. 4. The overall trends of the development change of the numerical simulation calculation results and the actual measured data in the field were basically the same, and the cooling law was similar. For the temperature measurement points at the same location, the measured temperature data were close to the values obtained from the numerical simulation. 5. Keeping the freezing time constant, any change in the starting brine temperature in the brine cooling plan showed almost no effect on the final formation of the effective thickness of the freezing wall, and the final effective thickness of the freezing wall was not related to the starting brine temperature. In the case of the termination brine temperature, the freezing curtain form did not change by only changing the freezing starting brine temperature. However, within the tolerable range of the freezing pipe, lowering the starting brine temperature increased the cooling rate of the soil and accelerated the freezing process. 6.