Temperature reduction for extra-long railway tunnel with high geotemperature by longitudinal ventilation

Abstract A wide geothermal anomalous zone exists around the Hengduan Mountains in China. The construction of railway tunnels in geothermal anomalous zones encounters the phenomenon of high geotemperature, which has serious impacts on personnel and equipment during the construction and operation of the tunnel. In this study, a convection-conduction model in a transverse section is built to represent a high-geotemperature tunnel with longitudinal ventilation. Taking the Gaoligongshan Tunnel as an example, the influence of ventilation frequency and longitudinal velocity on the ambient temperature in the tunnel is studied by numerical simulation. Then, a scale model test is carried out to study the temperature field of the surrounding rock and air flow in the tunnel with longitudinal ventilation. Finally, the experimental and numerical results are compared and analyzed. Results show that the mechanical ventilation frequency and ventilation velocity have a huge effect on the temperature field. In order to make the ambient temperature in the tunnel lower than 28 °C, the longitudinal velocity should not be less than 3.5 m/s and the ventilation frequency should not be less than 3 times a day. The experimental results have a good agreement with the numerical simulation results and validate the reliability of the numerical method.