Variation Law of Air Temperature of a High-Geotemperature Tunnel during the Construction

High geotemperature seriously impacts personnel and equipment during railway and expressway tunnel construction. In this study, the Nige tunnel in the expressway from Gejiu to Yuanyang in Honghe Prefecture was used as an example. Firstly, automatic temperature recording devices were used to monitor the variation characteristics of the tunnel temperature. Afterward, the variation characteristics of the temperature at 5-10 days and 150 days after tunnel’s completion were revealed. The results showed that the evolution laws of air temperature in each stage could be revealed by logarithmic functions of increasing type and decreasing type. Based on the monitoring over 5-10 days after tunnel’s completion, the temperature range was 26-44°C, and the highest temperature in the tunnel is located near the middle of the tunnel. The temperature fluctuation near the tunnel entrance is relatively small, while it fluctuates greatly near the tunnel exit. Based on the monitoring over 150 days, the air temperature was maintained between 16 and 31°C. The temperature near the tunnel entrance was high, while the temperature near the tunnel exit was low. The performance had a guiding significance for the design and construction of the high-geotemperature tunnel.