Influence of arch lattice-shell hood length on micro-pressure waves at portal of a high-speed maglev tunnel

The considerable increase in train velocity has intensified mutual aerodynamic effects between a train and a tunnel. How to effectively reduce the micro-pressure wave (MPW) amplitude at the high-speed railway tunnel exit is significantly important and has been recognized as an extremely challenging study, especially for the high-speed maglev tunnel when the train travels through it at 400 km/h or even more. To effectively mitigate the phenomenon of “sound explosion” caused by micro-pressure waves, this study provided a newly novel solution to mitigate the micro-pressure wave amplitude, which breaks up the traditional design idea and introduces a completely new arch lattice-shell structure inside the tunnel hood. In addition, the effect of the arch lattice-shell length on initial compression waves at high-speed maglev tunnel entrance and MPWs at exit were analyzed. The findings indicate that compared to the typical section-expanded tunnel hood, the new section-expanded lattice-shell hoods have a positive effect on the mitigation of micro-pressure waves emitted at the high-speed maglev tunnel exit. As the hood length increases, the alleviating effect is strengthened, resulting in a substantial decrease in the peak of the pressure gradient (Pg) and amplitudes of MPWs. When the section-expanded lattice-shell hoods are 50, 80, and 100 m in length, the pressure gradient peaks (Pg) are decreased by 6.2%, 34.9%, and 41.8%, respectively, while the corresponding amplitudes of MPWs are reduced by 9.4%, 46.8%, and 51.9%, respectively. Therefore, the new arch lattice-shell structure added inside the section-expanded tunnel hood can significantly mitigate the amplitudes of MPWs, which provides a newly novel solution for the tunnel hood design during the high-speed train passing through the tunnel at a higher speed.