Operating Environment and Pollutant Distribution in Xiang’an Undersea Tunnel

In order to clarify the distribution of environmental parameters and pollutants in the urban undersea road tunnel, a field test was carried out for the ventilation effect of Xiamen Xiang'an undersea tunnel. The atmosphere pressure, temperature and humidity, air speed, CO, NO₂, and PM concentration in the tunnel were tested during the peak and off-peak periods. Combined with the one-dimensional diffusion theory and the Fluent component transport model, the distribution of environmental parameters and pollutants along the traffic volume in the undersea road tunnel was studied. The results show that: (1) during the rush hours, the temperature increases gradually along the direction of traffic flow and reaches to 36℃ at the outlet. The humidity decreases gradually along the direction of traffic flow and reaches to 94% at the inlet. The CO, NO₂, and PM concentrations increase gradually with the direction of traffic flow and reach to maximum at the outlet, the maximum concentrations were 21.00 ppm, 3.73 ppm and 1.76 mg/m³, respectively. The PM concentration at the bottom of the V-shaped slope reaches to 2.03 mg/m³. According to the conversion formula of particulate matter concentration and extinction coefficient, the extinction coefficients at the outlet and the bottom of the V-shaped slope are 0.008 3 m⁻¹ and 0.009 5 m⁻¹ , respectively. The NO₂ and PM concentrations exceed the threshold value. (2) The maximum concentration of NO₂ during off-peak hours is 1.68 ppm, and the extinction coefficients at the outlet and the bottom of the V-shaped slope are 0.006 9 m⁻¹ and 0.007 7 m⁻¹ , respectively. The NO₂ concentration at the outlet and the extinction coefficient at the bottom of the slope exceed the threshold value.