## 1 Introduction  
The rapid development of electric vehicles (EVs) has introduced new challenges for tunnel safety, especially in the event of a fire. Compared to traditional internal combustion engine vehicles, EV fires are characterized by faster combustion, rapid fire spread, greater difficulty in extinguishing the fire, and the release of large amounts of high-temperature toxic gases. These factors could cause thermal damage to tunnel lining structures, leading to concrete spalling and affecting the normal operation of tunnels. Therefore, it is particularly important to study the fire characteristics of electric trucks and assess the fire performance of existing passive fire protection materials under such fire conditions. To understand the combustion characteristics of electric vehicle fires, researchers both domestically and internationally have conducted full-scale experiments and numerical simulation studies on electric vehicles. [PERSON] et al. [1] carried out a battery core ignition test, battery module fire test, and electric vehicle fire test in the safety project and evaluated the fire protection program. [PERSON] et al. [2] studied and solved the problem of vehicle fires caused by thermal runaway of lithium-ion batteries. The maximum external flame temperature reaches 843.6 \({}^{\circ}\)C, and the maximum compartment flame temperature reaches 696.8 \({}^{\circ}\)C. [PERSON] et al. [3] summarized the published vehicle ignition test results, including pure electric vehicles, including peak HRR, THR, H, and loss of mass. In addition, [PERSON] et al. [4], [PERSON] et al., [PERSON] et al. [5] [PERSON] et al. [6], and [PERSON] et al. [7] conducted combustion tests on pure electric vehicles. [PERSON] and [PERSON] [8] discussed in detail the standardization of pure electric vehicle testing. [PERSON] et al. [9] (2015) used propane sand burners to ignite several electric vehicles and measured the heat release rate (HRR) and temperature in electric vehicle fires. They discussed some parameters that may affect HRR in the experiment, such as electric vehicle type, state of charge (SOC), and battery capacity. [PERSON] [10] (2017) studied the combustion behavior of pure electric vehicles under mechanical shock. After the accident, the battery pack immediately emitted smoke, and 9 min later, the Battery Electric Vehicle (BEV) was engulfed by flames. The highest temperature measured during the test was above 1000 \({}^{\circ}\)C. Due to the high cost of using full-size electric vehicles for fire tests, some fire risks of electric vehicles are inferred by simulating the fire test of electric vehicle battery packs. [PERSON] et al. [11] simulated and calculated eight kinds of lithium batteries for new energy vehicles and measured the temperature under the tunnel ceiling. [PERSON] et al. [12] analyzed the flame combustion characteristics, flame propagation, and cabin smoke of pure electric vehicles. It was found that the smoke entered the cabin through the gap of the body, and the smoke concentration reached 100% within 40 s. [PERSON] et al. [13] simulated the influence of door opening on the development of bus fire and personnel escape and found that the key time for passengers to escape was within 20 s after the door was opened. [PERSON] et al. [14] studied the combustion characteristics and heat release rate of pure electric vehicles. The formula is reasonable for estimating the heat release rate of pure electric vehicles. [PERSON] et al. [15] numerically simulated the fire process in the engine compartment of a bus and found that the faster the wind speed, the shorter the time required for the bus fire to reach the maximum heat release rate. The integrity of tunnel lining structures is affected by the scale of the fire. In response to thermal damage caused by fires, researchers have conducted extensive studies on fire protection materials for tunnels. [PERSON] et al. [16] developed a new fire-resistant binder coating that can withstand both fire loads and traffic loads.