Abstract
Deepening our understanding of temperature and stress evolution in high-temperature tunnels is indispensable for tunnel support and associated disaster prevention as the rock temperature is remarkably high in hot dry rock (HDR) utilization and similar tunnel engineering. In this paper, we established a two-dimensional thermal–mechanical coupling model through RFPA2D-thermal, by which the temperature and stress field of the surrounding rock in a high-temperature tunnel with and without thermal insulation layer (TIL) were studied, followed by the evolution of thermal cracks. The associated sensitivity analysis of the TIL and airflow factors were then carried out. We found that (1) the tunnel rock is unevenly cooled down by the cold airflow, which induces thermal stress and damages the rock element when it exceeds the tensile strength of the rock mass. Those damaged rock elements accumulate and coalesce into visible cracks in the tunnel rock as the ventilation time goes, reducing the tunnel stability. (2) TIL effectively reduces the heat exchange between the airflow and tunnel rock and weakens the cold shock by the airflow, delaying the crack initiation which provides efficient time to adopt engineering measures for tunnel supporting. (3) TIL parameters are of pivotal importance to the long-term cold shock by the airflow. Increasing the TIL thickness and reducing the TIL thermal conductivity both significantly enhance the thermal insulation effect. The results cover the gap in the study of cold shock in high-temperature tunnels, which is helpful in designs to prevent thermal damage in high-temperature tunnels.
Highlights
Tunnel hazards caused by extremely high/low temperatures, such as freeze–thaw damage in cold regions [1,2] and heat disasters in high-temperature zones [3,4,5], have always been an overwhelming concern [6,7,8]
Affected by the cold airflow, a cold front appears in the tunnel rock, disturbing the temperature field near the tunnel wall and forming a thermal disturbance circle [42]
[29], weakening the tunnel stability. Figure when it exceeds the tensile strength of the tunnel rock [29], weakening the tunnel stability
Summary
Tunnel hazards caused by extremely high/low temperatures, such as freeze–thaw damage in cold regions [1,2] and heat disasters in high-temperature zones [3,4,5], have always been an overwhelming concern [6,7,8]. The tunnel rock is cooled and frozen in the winter by cold airflow but heated and melted in the spring as the airflow temperature increases [7,16]. Such freezing–thawing cycles induce freeze–thaw damage, weakening the tunnel rock strength and reducing the tunnel safety [17]. Such damage is effectively prevented by installing TIL on the tunnel wall, which decreases the heat flux between tunnel rock and airflow due to low thermal conductivity [8,18]. Numerous studies have focused on the temperature variation before and after TIL installation by analytical [6,19], numerical [7,20], 4.0/)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
