Abstract
The work gives the study results for 1:10 scale physical models of the road tunnels. The tunnel slope changes from 0 to 10% with a 2% spacing. As the models show, the fire strength varies within the range of 5 to15 MW with 5 MW increments. The properties of the tunnel geometry in nature are as follows: cross-sectional area: 46.7m2, length: 120 m, width: 8.5m, height: 5.5m and width and height ratio: 1.54. The models are made of 2 mm-thick stainless-steel sheets. We studied the nature of the spread of smoke, the variation of critical velocity depending on the tunnel slope and the characteristic value of such variation - the grade correction factor. The observation over such values is done depending on the air temperature variability in the tunnel model. The measurements are made with K-type thermocouples with open and closed detectors. Maximum temperature measurement is 800°C. The thermocouples are located in the holes provided in the ceiling of the tunnel model. The distance between the holes is 5 and 10 cm what corresponds to the natural length of the tunnel of 5 and 10 m. Fire is modeled by using the natural gas. The indications of thermocouples and air and gas meters are measured simultaneously and the primary analysis and the digital data transmission are provided with a Data Taker DT85 data logger. The gained results may be used to develop ventilation and emergency management projects for transport tunnels as well as to train personnel and rescuers.
Highlights
The critical velocity of ventilation and the opposite diffusion of smoke in the fresh air current are important technological values in ventilation projects that determine the ventilation efficiency
The prediction of the critical velocity and backlayering length using the grade correction factor is done according to well-studied fire spread scenarios in the horizontal tunnels
We studied the nature of the spread of smoke, the variation of critical velocity depending on the tunnel slope and the characteristic value of such variation - the grade correction factor
Summary
The critical velocity of ventilation and the opposite diffusion of smoke in the fresh air current (backlayering) are important technological values in ventilation projects that determine the ventilation efficiency. The prediction of the critical velocity and backlayering length using the grade correction factor is done according to well-studied fire spread scenarios in the horizontal tunnels. We studied the nature of the spread of smoke, the variation of critical velocity depending on the tunnel slope and the characteristic value of such variation - the grade correction factor. The observation over such values is done depending on the air temperature variability on the tunnel model. The gained results may be used to develop ventilation and emergency management projects for transport tunnels as well as to train personnel and rescuers
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