This study analyzed the unique aspects of smoke movement and control requirements in metro tunnel fires, and summarized the key scientific issues in the research of metro tunnel fires. This study reviewed the research progress and achievements of domestic and foreign scholars in various aspects including metro train fire combustion and plume behavior, smoke temperature distribution characteristics under the tunnel ceiling, smoke control characteristics, and characteristics of personnel evacuation. It highlighted the importance of integrating traditional subway section smoke control systems with new technologies such as artificial intelligence and the internet of things to enhance section fire prevention and control capabilities, which is deemed a crucial direction for future research.

To provide a scientific basis for emergency responses to tunnel fire safety in our country, a systematic exposition has been conducted on the current status and progress of research in four areas: the characteristics of smoke behavior in highway tunnel fires, tunnel fire prediction technologies, tunnel fire detection and early warning technologies, and tunnel fire control technologies. To ascertain the combustion behavior and smoke spread characteristics of multiple fire sources in highway tunnels under the influence of complex coupled factors; to develop digital and intelligent tunnel fire prediction technologies based on advanced algorithms and techniques such as deep learning, AI data, and big data analytics; to employ next-generation information technologies like the internet, Internet of Things, and cloud computing to achieve rapid, real-time monitoring and intelligent early warning for tunnel fires; to develop integrated tunnel fire control technologies that combine fire extinguishing materials, smart emergency devices, multifunctional ventilation smoke exhaust technology, and intelligent evacuation systems; to establish a "comprehensive-efficient-collaborative" emergency technology system for the entire process of highway tunnel fires.

Based on a large-diameter tunnel in Jinan, a full-scale numerical analyze model was performed to analyze the temperature field distribution, structural deformation and internal force distribution of the shield tunnel in fire. A thermal-mechanical coupling analysis method for shield tunnel lining structures was proposed. The results showed that the temperature of the inner heating surface area was significantly higher than the outer surface during fire, 300 mm part of the lining from the inner heating surface was not affected by fire; The lining expanded due to the heating in fire; The deformation of the vault and the bottom gradually decreased, the horizontal deformation of the arch waist continued to increase, some segment joints were significantly opened under the effect of fire. The stress of lining entered the yield state from the heating surface, while stress redistribution developed and connection bolts partially yield; The axial force of overall structure decreased and the bending moment increased dramatically, the bending moment of the arch waist even doubled compared with before.

In order to cope with the challenge of smoke control in tunnel fire caused by extreme rainfall, a scaled tunnel fire test platform was established based on Froude similarity criterion, and the law of smoke movement, vertical temperature rise and stratification of smoke under the effects of rainfall and longitudinal ventilation were investigated. The results showed that the longitudinal airflow induced by rainfall would hinder the movement of smoke to the rainfall side. As the rainfall intensity increased, the smoke was gradually controlled on the ventilation side, and the thickness of the smoke layer increased. After longitudinal ventilation running, the smoke was affected by both rainfall-induced airflow and forced ventilation airflow. The mixing of hot smoke and cold air intensified under the combined effect of the two airflows, and the thickness of the smoke layer increased. As the longitudinal ventilation velocity continuously increased, the smoke was gradually controlled at the rainfall side, and the smoke settled to the lower space of the tunnel. The increase of rainfall intensity and ventilation velocity destroyed the smoke stratification. When the longitudinal ventilation airflow was equal to the rainfall-induced airflow, the smoke stratification could be maintained stable.

To evaluate the influence of fire-retardant coating on the fire resistance of assembled frame tunnel, the temperature field distribution law of tunnel joint components coated with intumescent fire-retardant coating was analyzed by fire test, and the influence of fire-retardant coating on the temperature, deformation and damage of assembled frame tunnel under fire was studied by finite element numerical simulation. The results showed that the fire-retardant coating hindered the heat transfer to the tunnel lining, greatly reduced the temperature peak of the tunnel lining, and delayed the time of the temperature peak. The thickness of fire-retardant coating affected the heating rate and temperature peak of tunnel lining under fire, but when the thickness of the intumescent fire-retardant coating was greater than 10 mm, changing the thickness of fire-retardant coating couldn't effectively reduce the deformation of tunnel under fire. The maximum deformation of the prefabricated frame tunnel under fire was the mid-span position of the roof, and the most serious damage was the position of the tunnel joint, which could indirectly improve the fire resistance of the prefabricated frame tunnel by optimizing the mechanical performance of the joint structure.

Addressing the unpredictability of tunnel fire accidents, this paper presented a dynamic quantification approach to ascertain the probabilistic metrics of traffic tunnel fires, complemented by a statistical case study analysis. Causal analysis of tunnel fires identified vehicles as the principal disaster-inducing factors. Taking into account the conditions of the vehicles and the environmental impact within the tunnel, the individual fire frequency for each vehicle type was corrected. Then synthesizing above modification value with the number of vehicles inside the tunnel could obtain the tunnel's vehicle fire probability, which was amalgamated with the statistical probabilities of other incendiary events to construct a probabilistic quantification model for tunnel fires. Two empirical case studies analysis were conducted on a specific tunnel, resulting in the fire probability distribution within a 24-hour period. This achieved a dynamic quantification of the potential for fire occurrence, which provided a basis for real-time risk identification and accident prevention of tunnel fires.

Inorder to solve the heat damage caused by high temperatures in construction tunnels at high temperatures, based on the construction of the Jianshui(Gejiu)to Yuanyang section of the Honghe Hani and Yi Autonomous Prefecture in Yunnan Province, the temperature field of the tunnel under ventilation and ice cooling was numerically simulated using CFD software to compare and analyze the effect of cooling measures on the Nige Tunnel. Fluent was mainly used to establish a ventilation model for construction tunnels. Under the same air volume, a comparative analysis was conducted on the cooling effects of two ventilation methods combined with ice cooling under different ventilation air volumes. The results showed that when the surrounding rock temperature was 45 ℃, for the two ventilation and cooling methods assisted by ice, arch top pressure ventilation and side wall ventilation could not effectively control the air cooled by ice blocks near the palm face. Cold air was easily carried away by the return air, and the reduced temperature was not easy to maintain. On the other hand, wind curtain ventilation could control the low-temperature air cooled by ice blocks near the palm face, and the wind curtain ventilation method could reduce the temperature near the palm face by 3~5 ℃ more than the pressure ventilation method, and the cooling range was wider and more stable, with a more significant cooling effect.

In order to figure out the most-dangerous fire location and the disaster prevention design for curved tunnels, the typical fire scenarios, the factors affected critical velocity, as well as the disaster-prevention jet fan configuration of curved tunnels was discussed in this paper. The results showed that: The disaster prevention ventilation design for curved tunnelsshould be considered in case of the fire accident occurred at the convex wall in the steady stage of curve. The maximum critical velocity of curved tunnels was higher than that of the straight tunnel. Therefore, the correction coefficients on fire location, curve radius and tunnel slope for critical velocity of curved tunnelswere proposed respectively. Moreover, the number of operating jet fans for disaster preventionof curved tunnels was higher than that of the straight tunnel andthe calculation method for the number of operating jet fans for disaster prevention in curved tunnels was proposed.

To optimize and control the over/under-excavation phenomena observed in the excavation of flat and super-large cross-section tunnels using the drill and blast method. A highway tunnel served as a case study, where numerical models for tunnel sections with grade Ⅲ and Ⅳ surrounding rock were established. The blasting process of the tunnel cross-section was replicated, and field-measured data were utilized to validate the numerical models. Analyses were performed on the variations in blast damage nephograms, blast profiles, maximum and average over/under-excavation distances, and over-excavation areas across different blasting schemes. These analyses quantified the impact of varying peripheral and cut hole spacings, as well as the charge quantities in blast holes, on the over/under-excavation during tunnel blasting. Subsequent to these analyses, the blasting schemes were optimized. By integrating numerical simulation outcomes with field-measured data, an optimal construction scheme was deduced that effectively minimizes over-excavation: the peripheral hole spacing was adjusted to 1 m for grade Ⅲ surrounding rock and to 0.8 m for grade Ⅳ.

To solve the problem of local damage and water seepage and leakage of lining structure caused by the longitudinal uneven deformation in shield tunnel, the influence law of construction time of the secondary lining and the reasonable construction time were researched in this paper. A three-dimension longitudinal refined numerical model of shield tunnel with double-layered lining was established, and the mechanical properties of the bolts and the interface between segment and secondary lining were realistically simulated. The deformation degree of segment lining when the secondary lining was constructed was used as the construction time of secondary lining, and the influence of the construction time of secondary lining on the longitudinal mechanical properties of double-layered lining shield tunnel was analyzed through the longitudinal equivalent flexural stiffness, longitudinal deformations and longitudinal internal forces of shield tunnel. The researches shown that the ability of shield tunnel structure to resist longitudinal deformation was improved and the longitudinal internal force of segment lining was reduced owing to the construction of secondary lining. The earlier the construction time, the better the effect. However, the secondary lining load-bearing became prominent and the load-bearing capacity of segment lining could not be utilized sufficiently when the secondary lining was constructed early, resulting in a waste of structural capacity. Considering the longitudinal internal force situation of the double-layered lining structure, the reasonable degree was introduced as the judgment criterion, and the reasonable construction time of secondary lining was determined to be 37.5%-62.5%. In this condition, the segment lining deformation was within the tolerance range, and the requirements of engineering economy and structural reliability of tunnel structure could be satisfied at the same time.