Optimization of smoke exhaust efficiency under a lateral central exhaust ventilation mode in an extra-wide immersed tunnel

Abstract

This study focused on increasing the efficiency of the smoke exhaust system of an extra-wide (eight-lane, dual-directional) immersed tunnel with a specific quantity of exhaust. The Shenzhen-Zhongshan immersed tunnel was selected as the application example. A numerical simulation based on fire dynamics simulator was conducted. In the model, the concrete structure of the main body of the immersed tubes was not altered. The adoption of supplementary exhaust ducts increased the efficiency from 73% to 98% under the condition of no longitudinal wind. When a 50-MW fire occurred between two adjacent ducts, with a longitudinal wind velocity of 2 m/s, the efficiency reached 88% or more when the two ducts were opened. Furthermore, a safety evacuation path was developed. The results suggest that the addition of supplementary exhaust ducts combined with a rational longitudinal wind velocity is necessary for an extra-wide immersed tunnel.