## 1 Introduction
Static strength tests and Richtlinien fur den Ausbau von Brucken und Tunnel (RABT) fire load tests were conducted using a liquefied petroleum gas (LPG) furnace. The results indicated that the optimal thickness of the fireproof coating material is 30 to 40 mm. This material not only improves fire resistance but also exhibits excellent strength. [PERSON] et al. [17] designed a potassium-based geopolymer (k-geopolymer) prepared by mixing FeNi slag doped with pure alumina with a highly alkaline potassium hydroxide aqueous phase. The performance was evaluated by applying a 5 cm thick passive fireproof layer on concrete slabs. The results showed that the designed k-geopolymer exhibited excellent fire resistance in small-scale passive fire tests. The material helped maintain the structural integrity of the concrete slabs and kept the temperature at the geopolymer/concrete interface below 100 \({}^{\circ}\)C. [PERSON] [18] developed an experimental evaluation method to determine the required thickness of passive fire protection for high-strength concrete tunnel linings under RABT fire loads. The study found that a 30 mm thick layer of volcanic ash could prevent concrete spalling and limit the surface temperatures of the reinforcement and concrete to below 160 \({}^{\circ}\)C and 300 \({}^{\circ}\)C, respectively. Additionally, he discovered that the maximum effective thickness of the fireproof layer is 55 mm, beyond which the concrete protective layer no longer influences the temperature development inside the reinforcement. [PERSON] [19] pointed out that effective coatings can significantly improve the fire resistance of tunnels. [PERSON] [20] and [PERSON] et al. [21] estimated thermal insulation layers can effectively reduce the air temperature in high-temperature tunnels. However, this method has limitations. The maximum efficiency is achieved when the thickness of the insulation layer is between 4 and 6 cm. To address this limitation, [PERSON] et al. [22] proposed installing a corrugated steel shell between the insulation layer and the tunnel. They found that the shell effectively prevents the tunnel lining from spalling, and its thermal insulation performance can reach between 101.94% and 107.14%. In summary, previous research has primarily focused on the combustion characteristics of lithium batteries in electric vehicles, full-scale fire tests of electric vehicles, and ways to enhance the passive fire protection systems of tunnels. However, studies specifically addressing the fire characteristics of lithium battery electric trucks and the potential impacts of such fires on different lining insulation materials remain relatively scarce. Therefore, to effectively analyze the combustion mechanisms of electric truck fires and prevent potential damage from high temperatures on tunnel lining structures, this paper utilizes PyroSim software to simulate the thermal runaway process of a lithium battery pack in an electric truck within a tunnel. It analyzes the characteristics of the combustion of the lithium battery pack and compares the temperature field variations of different lining insulation materials under these fire conditions, ultimately evaluating the most fire-resistant lining materials to mitigate damage from severe fires to tunnel lining structures.