Exploring the Feasibility of Ventilation without Shafts for an Ultralong Subsea Tunnel in the Bohai Strait Channel

The Bohai Strait Channel (BSC) is a strategic infrastructure project connecting the Shandong Peninsula and northeastern China. One challenge related to building the BSC tunnel portion is that ventilation shafts cannot be constructed due to certain limitations, which leads to a barrier for ventilation design. To explore the feasibility of ventilation without shafts, we first compare the tunnel ventilation design methods in China and the European Union. We also present the development process of emission standards, base emission rates, and design concentration values. Then, a new ventilation calculation for the BSC tunnel with reference values from the World Road Association (PIARC) is presented. The results show that the longitudinal ventilation design without shafts is feasible under normal traffic conditions when adopting values designed by PIARC under both the Chinese method and the European method. Furthermore, the influence of new energy vehicles and the necessity of ventilation rate on ventilation design are discussed. We suggest considering new energy vehicle fire situations and ignoring the ventilation rate for BSC tunnels. We hope to provide a strong reference for the ventilation design of BSC tunnels and for the improvement of relative ventilation codes in China.