New Delhi, June 13 (PTI) The National High Speed Rail Corporation Limited (NHSRCL), which is constructing the Mumbai-Ahmedabad bullet train corridor, is building 16 ventilated hoods at both ends of eight mountain tunnels to regulate the booming sound generated by train operations.
Officials said the technology is a first for India, as existing railway tunnels do not require ventilated hoods because conventional trains operate at much lower speeds. The bullet train will run at a maximum speed of 320 kmph.
The 508-kilometre corridor passes through challenging terrain and includes seven mountain tunnels in Maharashtra and one in Gujarat. An expert associated with the project said when a high-speed train enters a tunnel, it pushes a large volume of air ahead of it, similar to a piston moving inside a cylinder.
He said, “This sudden compression of air generates pressure waves that travel through the tunnel. If not properly managed, these pressure waves can create a booming noise when the train exits the tunnel.” Outlining the benefits, engineers said tunnel hoods act as a transition zone between the open environment and the confined tunnel space.
They said by allowing air to enter and exit more gradually, the hoods help control pressure changes and improve the system’s overall aerodynamic performance.
The NHSRCL, in a press statement, highlighted several advantages of tunnel hoods, including minimising tunnel boom and noise generated by high-speed trains as they exit tunnels, reducing disturbance to surrounding communities, and supporting the safe and efficient operation of trains travelling at very high speeds.
“In simple terms, the tunnel hood helps the train and the air adjust to each other gradually rather than abruptly, making high-speed rail travel quieter, smoother and more comfortable,” the NHSRCL said.
“One of the distinctive features of these tunnel hoods is carefully designed pressure-relief vents or windows,” it said. These windows or openings allow a portion of the compressed air to escape gradually into the atmosphere as a train enters the tunnel.
This reduces the intensity of pressure waves, minimises tunnel boom and helps maintain smoother airflow. Tunnel hoods are a common feature on high-speed rail systems in countries operating bullet trains, where trains travel at speeds exceeding 300 kmph.
“Their adoption on the Mumbai Ahmedabad bullet train project reflects the use of advanced engineering solutions and international best practices to ensure world-class standards of safety, comfort and environmental performance,” the NHSRCL said. PTI JP ASD ASD
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