## 4 Conclusions  
The tunnel insulation lining structure plays a key role in the tunnel fire protection system. After the fire, the damage to the tunnel fire protection material will affect the repair and recovery speed of the tunnel. In this paper, the numerical simulation method was used to simulate the fire scene of the new electric truck and the combustion engine truck in the tunnel. The heat release rate, temperature, and smoke distribution of the fire were analyzed so as to compare the combustion characteristics of different types of vehicle fires. Based on the electric truck fire, the temperature distribution characteristics and fire resistance of different lining materials under high-temperature conditions were studied. The main conclusions are as follows:  
1. Through the simulation analysis of different types of vehicle fires, the results show that electric trucks show higher heat release rate and temperature than combustion engine trucks in tunnel fires and release a large amount of toxic gases and smoke. This shows that the fire of electric trucks is more dangerous in the tunnel environment, and special attention should be paid to its fire safety performance.
2. Through the temperature distribution curves, material properties, and incident heat flux of five different fireproof lining materials under heat, it was found that, under the same fire intensity and other boundary conditions, the amount of heat transferred by each material is influenced by its thermal conductivity and emissivity.
3. Among the five thermal insulation lining materials, SiO2 gel material is more effective than others in reducing the amount of heat entering the lining during tunnel fires, thereby minimizing fire damage to the support structure and ensuring the safety of the lining and the integrity of the tunnel.
4. In this study, the tunnel fire caused by lithium battery vehicles was simulated and analyzed, and five kinds of lining fire-proof materials were evaluated to lay the foundation for the follow-up work. Future research will further explore the mechanical performance of lining structures in extremely high-temperature fire environments under different ventilation conditions and lining thickness combinations so as to optimize the fire resistance design of tunnel lining structures and provide a more accurate and scientific reference for fire risk assessment.  
Figure 15: Incident heat flux 10 m downstream during a fire.  
**Author Contributions:** Study conception and design, X.L. and Y.C.; data collection, Y.C.; analysis and interpretation of results, X.L. and Y.C.; draft manuscript preparation, Y.C. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research was funded by the Shaanxi Province Special Funds for Technological Innovation (grant number 2021 QFY04-02), the Special Funds for Central Administration Guiding Local Science and Technology Development of Shaanxi Province (grant number 2021 ZY-QY-08-04), the Research Program of Shaanxi Anjian Investment Construction Co, Ltd. (grant number KY-2022-B15,B16), Special Key Research Project of Integration of Industry and Innovation Chain of QINCHUANGYUAN Industrial Cluster Programme (grant number 2023 QCY-LL-24), 2024 Henan Province Key Research and Development Project (grant number 241111322100), and Shaanxi Provincial Department of Transportation 2023 Annual Traffic Science and Research Projects (grant number 23-100K, 104K).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Data are contained within the article.  
**Acknowledgments:** The author sincerely appreciates the valuable suggestions provided by the reviewers.  
**Conflicts of Interest:** Author [PERSON] was employed by the company Shaanxi Anyite New Material Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.