Numerical study on temperature distribution of tunnel structure in fires

A series of simulations with different heat release rates (HRRs) are conducted in a full-scale horseshoe-shaped tunnel model. Thermocouples are arranged in 21 cross-sections of the tunnel to obtain entire temperature field. The prediction formulas of the ceiling maximum temperature and the longitudinal temperature attenuation beneath the ceiling are obtained, which are consistent with the model of Albert and Gong. It is found that the dimensionless transverse temperature rise distribution under the semicircular ceiling conforms to the Boltzmann curve, but the coefficients of the fitting formula are different for the near field zone and the far field zone. Transverse temperature distribution in the sidewall part can be regarded as constant, which is equal to the temperature at the bottom of semicircular ceiling in most engineering applications. A prediction model is established to estimate the temperature of each position of tunnel structure. It provides a more accurate and detailed temperature field prediction method for tunnel fire prevention and structural damage research.