2007-08-24 19:32:56 · 11 answers · asked by cookiesmom 7 in Science & Mathematics ➔ Engineering
so they don't fall in. try turning one on its side and making it go through the hole, it won't.
2007-08-24 19:40:52 · answer #1 · answered by THE GOOD NIGHT 6 · 4⤊ 1⤋
Lots of weird answers above, and most of them at least partly wrong. The correct answer is that round is the only shape that will ensure that the lid cannot fall through the rim. It could really injure someone working below.
It has nothing to do with construction economy. Check out a construction project where a new pipe gallery or cable vault is being dug and filled. The amount of earth excavated will be five to ten times the amount of the manholes when the project is finished.
2007-08-26 00:40:56 · answer #2 · answered by aviophage 7 · 0⤊ 0⤋
Manholes are round because it takes the least mount of effort to make the biggest possible opening. Let's say you need to cut a hole in the ground and you need 10 sq ft of area to get your equipment through the hole. Do you cut a circle or a square? the perimeter of a square with a 10 ft area is 20 ft. The circumference of the circle with a 10 ft area is only 11.2 ft (almost half as much). So you would cut a circle.
2007-08-25 02:49:30 · answer #3 · answered by Skrap 3 · 1⤊ 2⤋
A square manhole could be rotated in such a way so that it would fit into the the hole it was covering and fall through.
This can't happen with a round one.
Saw that on tv once.
2007-08-25 02:41:33 · answer #4 · answered by Anonymous · 2⤊ 2⤋
Easy question! So the covers don't fall in! Any other shape could be a hazard from the covers falling into the hole and injuring someone.
2007-08-25 02:42:10 · answer #5 · answered by Mr. Versatile 4 · 1⤊ 1⤋
Any other shape can drop thought the hole when turned at an angle sideways.
Safety
2007-08-25 02:41:05 · answer #6 · answered by jim 5 · 3⤊ 1⤋
so the cover does not fall in. there may also be a hose that fits just right in a hole that size but im not sure.
2007-08-25 05:06:55 · answer #7 · answered by Jerome54 5 · 0⤊ 1⤋
Because so many men are round. But then again, many men are square too.
Gee I dont know...
2007-08-25 07:03:15 · answer #8 · answered by Anonymous · 0⤊ 1⤋
Optimum access hole size for least circumference (manhole material).
2007-08-25 02:38:38 · answer #9 · answered by Gruntled Employee 6 · 0⤊ 4⤋
Because they cost to much to make them look like billy idol.
Main reason is they cover round pipes.
falling into a hole is a stupid answer as a square cover can't fall into a Round Hole.
2007-08-25 02:40:36 · answer #10 · answered by Yoho 6 · 0⤊ 6⤋