Field study on pressure fluctuations and comfort analysis when high-speed train passes through large-slope tunnels and tunnel groups

Abstract

High-speed trains passing through 25 ‰ sloped tunnels and tunnel groups experience complex and varying pressure environments within the tunnel. When these external pressure fluctuations are transmitted into the carriages, they alter the internal pressure environment and affect the passenger comfort. In this paper, field measurements have been used to study the influences of tunnel lengths, slopes and tunnel groups on the interior and exterior pressure variation of the train and pressure comfort. The key findings reveal that the atmospheric pressure in single-slope tunnels changes linearly with tunnel altitude at a rate of 10.21 Pa/m. External negative pressures in the uphill tunnels and external positive pressures in the downhill tunnels demonstrate a linear and positive relationship with tunnel lengths. Tunnel slopes and tunnel groups worsen the pressure comfort environments. Additionally, during actual operation on a 25 ‰ uphill railway line, delayed valve closure upon tunnel entry and premature valve opening within tunnels significantly degrade the pressure comfort environment inside the train, resulting in ear discomfort for passengers. Hence, optimizing the logic for opening and closing pressure protection valves based on line characteristics is essential. These findings can provide valuable references for optimizing operating environments and pressure comfort in high-altitude, large-slope and multiple-tunnels lines.