Abstract
In cold regions, heat-insulating layers play a crucial role in frost prevention in tunnels. This paper presents a numerical study on the anti-freezing behavior of a cold region tunnel (the Dege tunnel) with heat-insulating layers. A numerical model based on the temperature field coupling theory is firstly proposed and validated using field test data of the Dege tunnel. Subsequently, a comprehensive parametric study is carried out to investigate the influences of heat-insulating layers on the temperature characteristics of airflows inside the tunnel, the surrounding rock, and the tunnel lining. Furthermore, a numerical investigation based on the proposed numerical model is carried out to propose reasonable design parameters of heat-insulating layers for different velocities of mechanical ventilation, and different heat-insulating materials for cold region tunnels. The numerical results show that using the heat-insulating layer can effectively reduce the heat transfer between the surrounding rock and the airflow inside the tunnel. It is also found that the design parameters for the heat-insulating layer are greatly affected by the tunnel ventilation conditions and heat-insulating materials.
Highlights
In cold region tunnels, damages from frost may cause cracking, peeling-off and ice-covering of lining systems, which may even lead to more serious consequences, such as tunnel discard.The damages from frost cause safety issues for public transportation, and increase maintenance costs of tunnels during operation
In 1998, Mai et al [14] studied the influences of ventilation velocity and external air temperatures on airflow temperatures in the Qinling mountain tunnel based on the heat transfer theory
To further investigate the influence of the heat-insulating layer on temperature fields of cold results in the deep surrounding rock is compared on the surface region tunnels, a parametric study presentedto in those the following section. of the secondary lining
Summary
Damages from frost may cause cracking, peeling-off and ice-covering of lining systems, which may even lead to more serious consequences, such as tunnel discard. In 1998, Mai et al [14] studied the influences of ventilation velocity and external air temperatures on airflow temperatures in the Qinling mountain tunnel based on the heat transfer theory Two years later, He et al [15] proposed a mathematical model for the heat convection between airflows and surrounding rocks based on turbulence equations, which was used to investigate the temperature distributions of airflows in the Qilian mountain tunnel. He et al [15] proposed a mathematical model for the heat convection between airflows and surrounding rocks based on turbulence equations, which was used to investigate the temperature distributions of airflows in the Qilian mountain tunnel They carefully examined the differences between using turbulence equations and laminar equations. A three-dimensional (3D) model was proposed based on the temperature field coupling theory (airflow-lining/heat-insulating layer-surrounding rock). The heat transfer between different physical domains is realized by means of convection through adjacent domain interfaces
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