Abstract

To systematically examine the effects of ambient wind speed on the fire behavior of inclined tunnel cables, this paper determines the combustion characteristics of ZR-RVV cable combustion parameters using synchronous thermal analysis and cone calorimetry. A 1:20 scaled tunnel platform was established based on Froude similarity criterion to conduct combustion experiments under varying wind speeds (0–0.7 m/s) and inclination angles (−30°–30°). Results indicate the ignition time of the cable decreases gradually with increasing external heating radiation intensity (25–50 kW/m2), with ignition at 295.1 °C. A modified Richardson number (Ri*) is introduced to quantitatively identify the dominant flow regime. It is confirmed that when |θ| ≈ 20°, Ri* ≈ 1, and the fire behavior transitions from “domination” (Ri* < 0.5) to “buoyancy-driven stack effect domination” (Ri* > 2). This critical inclination angle provides decisive guidance for fire source localization, smoke control, and exhaust design. Increasing ambient wind speed significantly reduces the fire temperature and dilutes the smoke; at a wind speed of 0.7 m/s, the maximum temperature drop at the ceiling monitoring point reaches 67%, while CO/CO2 concentrations decrease correspondingly. The findings provide a theoretical basis for smoke exhaust design and fire monitoring in tunnel fire protection.

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