Abstract
The branched tunnel with inclined mainline is increasingly common to link ground and underground transportation network. The smoke movement characteristics and critical velocity in branched tunnel with uphill mainline are still unclear. This work investigated the smoke back-layering length and critical velocity in branched tunnel with inclined upstream and horizontal downstream via model-scale (1/20) experiments. The mainline slope varied from 1% to 7%, and three bifurcation angles of 10°, 20° and 30° were considered. Results show that the increasing of the uphill mainline slope promotes the shorter backflow distance in inclined mainline that requires smaller wind speed to control smoke return. The smoke back-layering length monotonically ascends with the heat release rate, but the effect of bifurcation angle is fluctuant. The critical velocity is higher for greater heat release rate. The logarithmic function can well express the relationship between Q*/V*3 and L/Hc that the correction factor of bifurcation angle is used to modify the expression. A new model of critical velocity is characterized by considering the mainline slope and bifurcation angle. The proposed model for critical velocity shows good agreement with experimental results, which can apply to horizontal branched tunnel and branched tunnel with uphill mainline.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.