Why are piston relief ducts installed in the Channel Tunnel?
Why are piston relief ducts installed in the Channel Tunnel? 
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The Channel Tunnel is linking England and France beneath the English Channel. Crossing the violent English Channel via an underground tunnel has been one of mankind’s greatest engineering dreams.
This dream was fulfilled in 1990 after a massive tunneling and sophisticated railway work. This simple tunnel-train method has a very big technical issue. Can you spot it?
Train and spring experiment
Consider a child trying to push a toy train that's pressing against a spring. After pushing the train for some distance, the child will struggle to push it. The compressed spring is resisting the train.
What's the solution here? To solve this, imagine removing a section of the spring and reattaching the remaining portion. The child can now push the train further with less resistance.
Importance of the piston relief ducts
As a high-speed train passes through a tunnel, the air in front of the train gets compressed and creates high resistance against the train. The motion of the train would be extremely difficult due to this compressed air.
Similar to releasing a compressed spring, the solution involves venting the compressed air from the tunnel, which is managed by 194 piston relief ducts as shown.
I hope you understand the importance of piston relief ducts in channel tunnels.
Published On : October 29, 2025
Nice articles… please provide more articles like this on inshort news app
Thank you so much Prince Kumar! Glad you liked it 😊 I’ll definitely share more interesting articles like this soon.