Search

• Three 1.6 m (Length) × 1.6 m (Width) diesel oil pool fire tests were carried out on two URTS in hot summer. • Shafts exhausted out of much smoke, but backflow occurred farther away from the fire sources. • Temperatures/velocities under the ceiling decayed longitudinally with the power index law. • The measured mass flow rates out of unit shafts were in range of 0.31 ∼ 1.76 kg/s.m2. • Dimensionless number Ri′ was adopted to assess the smoke flow under the shafts. Shallow-buried urban road tunnels with shafts (URTS) have been operated in large cities of China, and successfully released the traffic congestion. Fire smoke is expected to exhaust out of one-side shaft groups driven by its own thermal buoyancy. However, full-scale test data of the fire smoke spreading in such tunnel are still lacked, and the prediction models needs to be verified. In hot summer of year 2020, three full-scale experiments were carried out on two URTS. A 1.6 m (length) × 1.6 m (width) iron pan was placed on ground with diesel oil used as the fire source. Testing systems were arranged under the ceiling, on top openings of shafts and at bottoms of shafts. Lots of smoke were rapidly exhausted out of the shafts closer to the fire sources, but backflow occurred at bottoms of those shafts farther from the fire sources being not conducive to smoke extraction. Other three results of full-scale fire experiments conducted on one URTS in cold winter are provided here for comparison. The findings are that both the ceiling smoke temperatures and the smoke spreading velocities decayed longitudinally well with the exponential function, and the downstream temperature attenuation coefficient k 2 were in range of 0.042 ∼ 0.188 being smaller than that of the upstream, also the hotter the weather, the smaller the k 2 ; maximum values on top openings of the shafts were measured to be 47 °C in temperature, 5 m/s in velocity and 180 ppm in CO concentration; mass flow rates of the unit shafts were measured to decrease away from the fire sources that were 0.30 ∼ 1.77 kg/(s·m2) in Fires 1 and 2, and 0.46 ∼ 1.27 kg/(s·m2) in Fire 3, also the prediction models were confirmed not to be accurate enough; number R i ′ differed among all unit shafts of Shaft 6#, and were about 13.5 ∼ 15.2 in Fire 1, but smaller to be about 1.4 in Fire 2. [ABSTRACT FROM AUTHOR]