저심도 도로터널에서 터널의 Hydraulic Diameter가 Plug-holing 현상에 미치는 영향에 대한 수치해석 연구

When the plug-holing occurs, the actual amount of smoke exhaust could not be able to satisfy the design criteria of the smoke ventilation. The plug-holing phenomenon is influenced by heat release rate, geometry of tunnel and shaft. However criterion of plug-holing has not yet suggested accurate criterion for the plug-holing. Especially, in previous researches, the effect of tunnel geometry was not considered, despite the smoke movement is influenced by hydraulic diameter of tunnel. In this study, we performed the numerical simulation to analyze the effect of the hydraulic diameter of a tunnel on plug-holing. Size of the subject tunnel, 1/7th geometrically scaled, is 7m long, 1.1 m high. Also, the tunnel width is varied from 0.8 m to 1.6 m to change the hydraulic diameter of the tunnel. Shaft has square cross section 0.4 m and height of shaft is 0.5 m. The factors such as the heat release rate have been held as a constant 40.14 ㎾. According to the numerical result, modified Froude number is suggested for estimating the occurrence of plug-holing by including the effect of the hydraulic diameter for shallow tunnels. Additionally, the critical value of the modified Froude number is suggested as 0.37 to 0.42 based on the results of the numerical simulation.