Tunnel facts for kids
A tunnel is an underground passage. Tunnels are like long tubes that go through the ground, under mountains, or even under water. People use them for many things. Some tunnels are for cars, and others are for trains. Sometimes, a tunnel helps ships move through. Other tunnels carry important things like communication cables, electricity cables, or even water pipes. Some special tunnels are even built for animals to cross safely!
Tunnels can be dug in many different types of ground. This can be soft sand or very hard rock. The way engineers dig a tunnel depends on the type of ground.
Contents
How Tunnels are Built
There are a few main ways to build a tunnel.
Digging Through Rock
When the ground is very hard rock, engineers often use a method called 'drilling and blasting'. They drill holes into the rock, place explosives inside, and then blast the rock away. This creates a path for the tunnel.
Another way to dig through hard rock is with a tunnel boring machine. This is a giant machine that slowly grinds and cuts its way through the rock, creating a smooth tunnel as it goes.
Cut and Cover Method
For tunnels that are not very deep, like some road tunnels or subway lines, engineers might use the 'cut and cover' method. First, they dig a big trench in the ground. Then, they build the tunnel structure inside this trench. Finally, they cover the top of the tunnel with soil and rebuild the surface above it. It's like digging a ditch, building a box in it, and then burying the box.
Building Under Water
Building tunnels under water is very tricky! Sometimes, engineers sink large, pre-built sections of the tunnel into a trench at the bottom of the water. They then connect these sections together. Other times, they use special machines that can dig through the ground while keeping the water out.
Building tunnels is a huge civil engineering project. It can cost a lot of money and take many years to plan and build, especially for very long tunnels.
The Channel Tunnel is a famous example. It connects France and England under the sea and is about 50 kilometers long. The Gotthard Base Tunnel in Switzerland is the longest railway tunnel in the world.
Why We Build Tunnels
Tunnels are built for many important reasons:
- For Public Transport: Subway systems use a network of tunnels underground. This helps trains move quickly without getting in the way of cars or people on the surface.
- To Go Through Obstacles: If a railroad track or a road meets a big obstacle like a mountain, a tunnel is dug through it. This avoids having to go all the way around the obstacle.
- To Cross Water: Sometimes, a tunnel is built under a water obstacle instead of building a bridge over it. This can be useful for busy shipping lanes or in places where a bridge isn't practical.
- For Hidden Movement: Tunnels can connect different military areas. This allows people and supplies to move between them without being seen by others.
- For Essential Services: Tunnels are built for important infrastructure like electricity cables, water pipes, communication lines, and sewer systems. This protects them from damage and keeps them out of sight above ground.
- For Animals: In some places, tunnels are built under roads or railways to help animals cross safely without being hit by vehicles.
Images for kids
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Tunnel in Fort de Mutzig, France
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Utility tunnel for heating pipes in Copenhagen, Denmark
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Joralemon Street Tunnel on a 1913 postcard, part of the New York City Subway system
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The Baltimore Harbor Tunnel in Baltimore, which carries I-895, is an example of a water-crossing tunnel.
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Cut-and-cover construction of the Paris Métro in France
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A worker next to a tunnel boring machine used for the Gotthard Base Tunnel (Switzerland).
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1886 illustration showing the ventilation and drainage system of the Mersey railway tunnel.
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Illowra Battery utility tunnel, Port Kembla.
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Shark tunnel at the Georgia Aquarium.
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A utility tunnel in Prague.
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The upper-level traffic lanes through Yerba Buena Island, part of the San Francisco–Oakland Bay Bridge.
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The 1,659-foot (506 m) Donner Pass Summit Tunnel (#6) was used from 1868 to 1993.
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Liverpool Lime Street Approach. Some road bridges seen here are solid rock, acting as short tunnels.
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Small operational brick tunnel in France.
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The Gotthard Base Tunnel is the first flat route through a major mountain range.
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The Big Dig road vehicle tunnel in Boston, USA.
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The eastern entrance of the abandoned Sideling Hill Tunnel, Pennsylvania, USA in 2009.
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Tunnel formerly used for coal mining in New Taipei, Taiwan.
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View through a natural tunnel in South Korea.
See also
In Spanish: Túnel para niños
