Scale Model Experiments and Simulations to Investigate the Effect of Vehicular Blockage on Backlayering Length in Tunnel Fire

This study used model experiments and numerical simulations to investigate the backlayering length of a vehicle-blocked tunnel fire. The experimental setup included two types of obstacles (low obstacles and high obstacles), as well as three configurations: no obstacles, one side with a car obstacle, and two sides with a car obstacle. If there were vehicles on one side of a lane, it would have little effect on the elongation of the backlayer length. When there were vehicles on both sides of a lane, the elongation of the backlayer length was greatly reduced. In addition, the effects of the vehicular blockage ratio and blockage configuration on the properties of the backlayering length were investigated. We created Pattern A, where fire is was in the center, and Pattern B, where fire was on the side of the tunnel. In Pattern A, almost all obstacles could be approximated using the formula. When the vehicle blockage ratio of a single lane was small, an approximation formula for Pattern B was applicable. However, if the distance between stationary vehicles on the upstream side of the fire source was small, the backlayering length could have been longer than in the case with no vehicular blockage.

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