Abstract:

The ventilation resistance characteristics of confluence and distributary ramps of Xiangjiang Rivercrossing Tunnel on Yingpan Road in Changsha is studied by field monitoring, scale model experiment and software CFD numerical simulation; and then the influences of Reynolds number, air volume ratio and bifurcation angle on resistance characteristic of confluence and distributary ramps of the tunnel are analyzed so as to know the air flowing characteristics of urban underground passageway with bifurcated ramps. The results show that: 1) The air volume ratio and bifurcation angle are the key factors on the local resistance coefficients of confluence and distributary ramps. 2) The parameters of triplet joint component of ventilation pipe cannot be applied to characterize the variation of local resistance of confluence and distributary ramps. 3) The multiplefactor regression analysis of calculation results is carried out by least square method and software Matlab, which provides the expression equation of local resistance coefficient of confluence and distributary ramps of Xiangjiang Rivercrossing Tunnel on Yingpan Road in Changsha. The study results can provide reference for analysis of resistance characteristics of ventilation system and optimization of ventilation engineering design of urban underground passageway with complex structure.

Key words: urban bifurcate tunnel, confluence and distributary ramp, local resistance coefficient, scale model experiment, numerical simulation