why are manholes round?

Answer 1

To correspond with round manhole covers. The covers in turn are round because a round cover cannot fall in a round hole. The maximum diameter is the same at every cross-section of the cover and at every cross-section of the hole. And the maximum diameter of the cover is always greater than that of the hole. Therefore, the 50 lb chunk of iron can't fall 10 feet through the hole it came from and crush the skulls of the workers below.

There is another thing I wish to add. This question comes up often in job interviews; yes, I am not kidding! Various answers have been put forth, but the one I've stated above seems to be among the most popular.

Answer 2

I think manholes are made round is because it's more
stronger than a square type. When the force or pressure is concentrated on the center, it spreads out evenly to all and
equal sides of the round circle, thus holding or supporting it
better in strength. Besides, you can't easily fall into a round
manhole than in a square one.
So it's logical to make round manholes.

Answer 3

For safety Reason
You know the answer. That is why you are asking.
They are round because the perimeter is constant due to its circular shape. The perimeter of the lid is a bit bigger then the manhole's frame. The big circle of the lid does not go through the small circle
of the frame.
It is solely for Safety reasons.
Square Manholes have hinges.
Again, for safety reasons.
¿Satisfied?

Answer 4

physically speaking.......manholes are round because a circle is the strongest geometric shape.......with all the traffic that drives over the holes they are protecting you would have to use much more steel to reinforce a square lid than a circular one, which in turn would cost alot more.......so mathematically speaking and economically speaking the circle is by far the best design.

Answer 5

I think Mike's answer is right. And, it's easier to put them back right if they are round. Those things are HEAVY and it isn't as hard to line up a circle correctly.

Answer 6

because they are stronger than a square inch per inch . if you stop a car on the middle of a square it would bend in the middle easier, because all the force would be on the corners

Answer 7

bscause if a square plate was there it could fall in try and make circle fall through a hole almost the same size you cant

Answer 8

people are round

Answer 9

So there are no sharp corners to put someone's eye out?

Answer 10

So they won't fall into the hole when they're removed.