Ain Shams Engineering Journal (May 2023)
Spatial-temporal evolution principle of temperature field in a high-temperature geothermal highway tunnel
Abstract
The spatial-temporal evolution principle of the temperature field in a high-temperature geothermal highway tunnel is investigated, which aims to shed light on the thermal damage prevention for the high-temperature geothermal tunnels. Taking the Nige Tunnel, a high-temperature geothermal tunnel of Jianshui (Gejiu) to Yuanyang expressway in Yunnan Province as the research case, the temperature fields of air, lining and surrounding rock covering all the thermal damage grade sections are monitored. Furthermore, the numerical simulation is conducted to simulate the temperature field of the tunnel. The results show that 1) the temporal curve of air temperature inside the tunnel shows a slowly decreasing trend with the decrease of air temperature outside the tunnel. In contrast, the temporal curve of secondary lining shows a rapid increase-rapid decrease-stable-slow decrease trend. The temperature of surrounding rock experienced two stages of natural and slow decline. 2) In the spatial dimension, the temperature in the tunnel is distributed in an “n” shape along the longitudinal direction of the tunnel, and the temperature contour of the surrounding rock is parabolic, with the centerline located at the breakthrough point during the tunnel construction. As time progresses, the region where the temperature field of the surrounding rock decreases gradually develops to the interior. 3) The effect of the sprayed thermal insulation layer is significant: the temperature difference of secondary lining and initial support could reach 20.1 °C; the temperature inside the tunnel then reduces to the standard value. 4) There is no thermal insulation layer in the cable trench of the Nige Tunnel, and the “thermal bridge effect” appears. The cable trench needs a targeted design, and the research of electromechanical heat resistance should be paid more attention.
