Investigation on temperature distribution in cold region tunnels during the excavation and optimization for insulating layers

Abstract

Extra-long highway tunnels in cold regions experience frost heave disasters near the entrances, consequently, the designation of insulation layers is crucial in guaranteeing stability and safety. Temperature distribution functions as a pivotal indicator in assessing the onset of frost heave, which is notably influenced by airflow and water/ice phase transitions. In this study, a new coupled model was developed on the foundation of heat transfer, Richards equation, and aerodynamics theories, with the objective of predicting the spatiotemporal distribution of temperature within tunnels. k-ε equation was utilized to delineate the airflow movement and deformed geometry method was employed to simulate the excavation process. On-site monitoring of temperature was conducted at selected typical sections to validate the proposed model. Subsequently, the proposed model was utilized to determine the optimal thickness and length of the insulation layers in order to prevent frost heave damage to the lining. The findings indicate that the model introduced in this paper possesses the capability to accurately predict the temperature distribution within the tunnel, both axially and longitudinally. The optimal thickness and length of the insulation layer, as proposed for this specific environment under varying airflow velocities, can serve as pertinent references for the design of cold region tunnels.