## 5 Key Technologies of Geothermal Disaster Prevention and Control in Large-Buried Tunnels  
### Temperature Reduction Technologies  
The main temperature reduction methods used in high-temperature tunnels are: (1) Ventilation; (2) Watering, cold water, spray, and ice; (3) Refrigeration and air conditioner and mobile refrigeration station. These kinds of measures can basically meet the requirements of general high-temperature tunnels when they are used in combination. This paper mainly introduces the research progress of two cooling methods of ventilation and refrigeration, as well as their applications in high-temperature tunnels. [PERSON] et al. [102] stated that the temperature and speed of wind have a significant impact on the tunnel temperature distribution. [PERSON] [103] established a numerical model of 30 m construction tunnel to simulate sidewall forced ventilation, mixed ventilation and vault forced ventilation, respectively. By adjusting parameters such as air supply speeds and duct positions, the influences of ventilation methods and parameters on the cooling effect were understood. [PERSON] [104] compared the influences on temperature field and cooling effect under different wind supply temperature, wind supply speed, wind duct diameter, and different roadway parameters. [PERSON] [105] simulated the 1300 m long-high-temperature construction section of Sangzhuling Tunnel to observe the temperature field at different ventilation speeds. When the ventilation speed reaches 35 m/s, the cooling rate can reach 43.3%, and the temperature difference by ventilation can reach 22 \({}^{\circ}\)C, which is shown in Table 5.  
[PERSON] [106] set different ventilation speeds for simulation to analyze the cooling effect of ventilation speed on tunnel face when the wall temperature is 54 \({}^{\circ}\)C. [PERSON] et al. [107] analyzed the heat exchange law in the tunnel under ventilation, and established a prediction model for the tunnel face wind temperature, which was proved accurate by the comparative analysis between the prediction and the measurement of Qinling Tunnel. Underpinned by the Gaoligong Mountain High Temperature Tunnel, [PERSON] et al. [108] studied the ventilation by using the tunnel convection heat conduction model, where the ventilation effect of the shaft was considered, and the influence of different ventilation frequency and ventilation speed on the ambient temperature in the tunnel were analyzed, providing a reasonable cooling scheme during the tunnel operation period. In addition to ventilation, refrigeration can also achieve the purpose of tunnel cooling. As presented in literature [109], the research progress of cooling technology abroad is showing as follows:  
The first mine air conditioning system in the world was established in 1920 at the Morau Yolihejin Mine in Brazil, where centralized refrigeration stations were built on the surface. As early as 1923, Pendleton Coal Mine in England used a refrigerator to cool the air temperature of the working face. A refrigerating machine on the surface of the Radlod coal mine was installed in Germany in 1924. The MorroVelno mine in Brazil and the Robinson Well in South Africa were cooled in the 1930s by centrally cooling the air flow into the shaft. Large air flow cooling equipment was settled under the Loeberg mine in 1953. In the 1960s, \begin{table}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{**Ventilation Speed (m/s)**} & \multicolumn{2}{c}{**Temperature (\({}^{\circ}\)C)**} \\ \cline{2-3}  & **Before Ventilation** & **Ventilation after 300 min** \\ \hline
20 & 51 & 36.1 \\ \hline
25 & 51 & 32.5 \\ \hline
30 & 51 & 30.3 \\ \hline
35 & 51 & 28.9 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Temperature comparison before and after ventilation. centrally air-conditioning large mines were employed in South Africa. After a decade, refrigeration cooling is gradually popular in the Soviet Union, Japan, and other countries. South Africa firstly used ice as a carrier cooler in November 1985, and the cooling capacity was up to 628 MW.