What do subway tunnels look like? Why are most of them round?

Have you ever been curious?

What does the subway tunnel we take in daily look like?

Is it a rectangle, hexagon, semicircle or circle?

The answer is a circle

So why are most subway tunnels round?

Let’s find out today!

Want to know the answer to this question

We need to think in terms of mechanics in the subway

To facilitate understanding, let's first change our thinking

Why are chicken eggs and duck eggs round?

Because animals are smart

They use the round shape's "good pressure-bearing properties" to protect unborn babies

Same reason

The reason why circular space is widely used in tunnel construction

This is because the circular structure is evenly stressed and can equally withstand external pressure from all directions.

And transmit the forces to the center to prevent the tunnel from deforming

Image source: Tencent Video

If it is square

There will be stress concentration effect at the four corners, causing direct collapse

At the same time, the circular structure itself has strong stability

This can also be seen in the natural landscape.

Image source: Photo·New Vision

Therefore, most subway tunnels are circular.

Do you understand why most subway tunnels are circular?

Finally, a few tips

Tips

The subway has the advantages of high speed, saving ground space, and being green and environmentally friendly;

On October 1, 1969, China's first underground railway, designed and constructed independently by the Chinese, was completed and opened to traffic;

In the actual construction of subway tunnels, the drilling and blasting method and the shield method are generally used to excavate the tunnel;

Qingdao Metro Line 3 is the first metro line in Qingdao and the first metro line to be completed and put into operation in Shandong Province, China;

The Qingdao Jiaozhou Bay Subsea Tunnel is the longest subsea highway tunnel in my country and the third longest in the world.