Name: Why Do London's Manholes Keep Exploding?
Uploaded: 2020-04-01T01:20:22.000Z
Duration: 2 min 58 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

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the odds of a manhole in a London street suddenly exploding while you're next to it

And the company that handles the cables under London's streets

is spending a lot of money fixing them up.

But, yeah, about once or twice a month on average, somewhere in London,

But no-one wants to license security camera footage of actual pavement explosions

to just someone on YouTube, and no-one wants to be interviewed about it either.

So instead, we are going to create our own underground explosion right here

with the help of a friendly pyrotechnician.

And the easy answer to why London's pavements keep exploding...

well, it would be "electrical faults", and that's what the news often blames.

As seasons change, the ground is going to get warmer and cooler,

it's going to expand and contract, rain and subsidence will move the soil,

that is going to steadily wear out the 36,000km of electrical cables

and 100,000 electrical junction boxes that are under London.

Most of those were laid decades ago. It's a big city. Things will break.

But an electrical fault won't make an explosion.

If electricity goes somewhere it shouldn't,

then the circuit breakers that control the grid will detect that

The trouble is that there's a lot of other old stuff under London's streets.

A steady, slow gas leak in a pipe might not be detected for a while,

and in that time the gas can spread a long distance through narrow underground tunnels.

So if you've got gas in a tight underground space where it can't expand,

thank you, and an electrical spark to set it off...

under that cover there is a fuel source, not enough room for it to expand,

and something to make an electrical spark.

"The burst of flame, the flying manhole cover,

"at 1800 frames per second on a zoom lens it looks like it could do serious damage.

"But even this dramatised explosion, made with the help of a pyrotechnician,

"this worst-case-scenario... is actually not that bad.

"I tried to do the 'cool guys don't look at explosions' shot,

"and when you take away all this style..."

"It'd hurt if you were standing on it, sure,

"but like I said, it's not something to be worried about."

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Why Do London's Manholes Keep Exploding?

stuff

scenario

devastating

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