What is the Channel Tunnel?

A tunnel connecting England and France underwater.

How were Tunnel Boring Machines used?

To advance forward, support tunnel walls, and manage pressure.

To shuttle staff along the tunnel with higher air pressure.

Through piston relief ducts and a service tunnel for ventilation.

Folkestone in the UK and Calais in France.

Tunnel Boring Machines (TBMs) played a critical role in constructing the Channel Tunnel, utilizing hydraulic cylinders to advance, support tunnel walls, and manage pressure to prevent collapse or flooding.
The Channel Tunnel, connecting the UK and France, not only revolutionized cross-Channel travel with high-speed rail services but also overcame numerous challenges during construction, including complex geology, financial struggles, and safety concerns, ultimately becoming a profitable and iconic engineering feat.

What is the Channel Tunnel?
A tunnel connecting England and France underwater.
How were Tunnel Boring Machines used?
To advance forward, support tunnel walls, and manage pressure.
What is the purpose of the Service Tunnel Transport System?
To shuttle staff along the tunnel with higher air pressure.
How does the Channel Tunnel manage air pressure fluctuations?
Through piston relief ducts and a service tunnel for ventilation.
What are the rail terminals connected by the Channel Tunnel?
Folkestone in the UK and Calais in France.

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The Channel Tunnel, also known as the Chunnel or Le tunnel sous la Manche, opened in 1994, connecting England with France.
It is the longest underwater tunnel globally, allowing passengers and cars to cross the English Channel in just over half an hour at speeds up to 99 mph.
The tunnel faced challenges such as complex geology, air and water pressure management, and financial issues during construction.
Tunnel Boring Machines (TBMs) were crucial in the construction, with eleven machines used to create the three separate tunnels.
TBMs use hydraulic cylinders to advance forward, support tunnel walls, and manage earth and water pressure to prevent collapse or flooding.
Crews injected grout into the rock ahead of the machines to strengthen it and simplify drilling through softer soils.
The service tunnel led the construction, exploring geology on a smaller scale and ensuring proper alignment of the main tunnels.
The tunnel features two large rail tunnels, a service tunnel, crossover caverns, and cross passages for emergency escape.
Special vehicles called the Service Tunnel Transport System (STTS) shuttle staff along the tunnel, with higher air pressure to prevent smoke travel.
Piston relief ducts manage air pressure fluctuations caused by trains, while the service tunnel acts as a duct for fresh air and ventilation.

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Enormous chilling plants built on either side of the Channel Tunnel, with miles of pipes carrying chilled water at 95 F, 35 C throughout the tunnel for passenger comfort.
Air conditioners on trains further cool the tunnel for passengers, with heat rejected needing management by the tunnel cooling system.
The Channel Tunnel connects the UK and France with rail terminals in Folkestone and Calais, offering a shuttle for passengers to bring vehicles, connecting highways of both countries.
Passenger train services, including High Speed 1 (HS1) since 2007, allow travel from London to Paris and beyond through the tunnel.
The tunnel features a loop system for shuttle trains at each terminal, with a crossover on the French side to prevent uneven wheel wear.
The Channel Tunnel, a privately funded project, faced safety issues during construction, human costs, and challenges with illegal immigration, asylum-seeking, and budget overruns, but has since turned a profit and remains a significant engineering achievement.