Abstract: Cooling techniques such as increasing air supply, sprinkling water, and using ice blocks are commonly used when tunneling in areas with a high ground temperature. Because the long-distance air supply is difficult, a local cooling technology is proposed to effectively reduce the internal temperature of a tunnel. The local heat is transferred to the non-construction area through an air-cooled chiller, a surface cooler, and a cooling water circulation system device. The comparative calculation results show that the local cooling effect is far higher than that of ice blocks. Furthermore, the heat transfer in the tunnel is calculated theoretically, and the cooling parameters of the cooling system are obtained. The test is conducted in a long tunnel in China, with the test system 60 m away from the tunnel face, and a 20 kW chiller and an 8 kW surface cooler are used. The test results show the following: (1) the temperature of the outlet of the surface cooler is 27.9 ℃, which is 8.1 ℃ lower than that of the inlet one and meets the temperature requirements specified in tunnel construction; (2) the air supply distance and volume of the air outlet of the surface cooler are small, resulting from the low residual pressure of the surface cooler. According to the result of the field test, four optimization recommendations are made as follows: adding condensate water recovery device, installing dust removal equipment in the air inlet, optimizing the performance of system equipment, and improving the integration degree of the system.

Key words:

tunnel with high ground temperature, assistant cooling in tunnel, local cooling, air-cooled chiller