Why are manhole covers for sewers usually round?

The first reason is that a circle has an infinite number of diameters, each of which is equal in length. If the manhole cover is designed into a square or triangle and other irregular shapes, once it is not placed properly, it is easy to fall into the manhole, causing inconvenience to pedestrians. And the round manhole cover will not fall into the manhole no matter from that angle.

Another reason is that it is easy to carry, and you can walk away if you want to pick it up and roll it.

Because then people can fall! Won't get stuck.

The good of the circle is stolen, so the company of the manhole cover will not worry about no business!

To be honest, you're bored enough, of course, I'll tell you for a good reason, but there are two versions: 1: the normal version: because the circle is more stable than other shapes, it will not break when the material is too little at a certain angle, and the round one will not fall into the well, 2:

Funny version: The earth is round, so he is also round" hehe.

The cover of the sewer is round and square, not all the sewer manhole covers are round, on our side, the southern climate is humid and rainy, in order to facilitate drainage, the sewer cover in many places is a square cover. Of course, the main sewer cover is still mainly round.

Why are round lids so widely used?

The road administration in the urban area basically uses circular sewer manhole covers.

There will be a large number of pedestrians and vehicles passing on the road, and if you use a square manhole cover, the manhole cover is easy to fall after falling into disrepair, and there will be no signs to let passers-by know. Moreover, the gap on the square cover is also prone to accidents.

For example, in the case of the picture below, it is easy to step on the pit if you are not careful.

But the round lid is different, and we all know that the distance from the center of the circle to any edge of the circle is equal.

So even if there is a problem with the manhole cover, as long as it is not broken, it is difficult to fall from the sewer mouth.

Even if it is crushed and shaken by a passing vehicle for a long time and shakes out, it will not fall under the manhole cover again, but has become a special reminder sign to remind passing drivers and pedestrians to pay attention to ......

From the perspective of safety, it is obvious that the round square is more safe and reliable.

Therefore, many sewer manhole covers adopt a circular design.

However, this design is not only from the perspective of safety, but also takes into account the ease of transportation.

In order to ensure the quality of the manhole cover of Xiayuqing Bridge and make it have high compression, bending and impact resistance, it is generally thickness and strength. We can also see that the thickness of the sewer is very thick, generally one is about 70kg.

Imagine that such a heavy manhole cover would be very labor-intensive to unload from the car and then install it on the sewer wellhead.

But if it is round, it has one more advantage than the square one, after moving off the car, you can use the rolling method, "roll to the manhole cover", and then seal and reinforce it.

If you can't move it, get out," ......It has also become the second reason for the popularity of round manhole covers.

The third reason is from the perspective of anti-theft.

Qingmeng has mentioned earlier that the square cover can drain water better, and in order to achieve the drainage function, there will be more gaps, which provide convenience for the person who steals the manhole cover to commit the crime.

It is only necessary to pry up the manhole cover from the gap with an iron rod with a qualified load-bearing, and the cover of the sewer can be taken away from ......

Round, generally there will not be so many gaps, or even only a small leakage hole, it is more difficult to warp the whole manhole cover through one hole.

Due to the gaps in the square cover, it is easy to cause sand, soil, garbage, etc. to fall along the manhole cover to the sewer, resulting in the sewer blockage ......

So, for the above reasons, most of the sewer covers use round covers.

Because each of the circles is equal in diameter, if the manhole cover is made into a circle, the cover will not fall into the well from any angle.

There will always be one with the longest inner diameter in other shapes, such as a rectangle, whose diagonal is longer than the side length, and if the manhole cover is made into a rectangle, it is very likely to fall from the angle of the diagonal.

So the manhole cover of the sewer is always made round.

This question was first asked by Microsoft when it was recruiting employees, and the answer was this: any diameter of the lid would not be smaller than the circle in which it was placed, and the lid would not fall off. Any side of the square lid is shorter than the diagonal of the square circle where it is placed, but the lid falls off when it is erected.

This question is designed to test a person's ability to think differently.

This is a figure that has been determined after many attempts, only the circular manhole cover can not find the diagonal, no matter which point to the corresponding side of the distance is the same and take the square, its side length and its diagonal length is not the same, so when the manhole cover moves, only the round one is the safest. And the manhole cover made of the same material is also the largest circular area, if it is put on the wellhead, no matter how it is placed, it is slightly smaller than the diameter of the wellhead, so it can not fall downhole, and the staff operating in the well is safe.

Before this question, let's take a look at what's underneath the lid of Xiangjing. The hole under the lid is round, as the cylindrical shape best withstands the pressure of the surrounding land. Moreover, sewer access holes meant that there was enough space for one person to pass through, and the cross-section of a person climbing down a ladder was basically round.

So the round shape naturally becomes the shape of the sewer access hole. The round manhole cover is only to cover the circular opening.

Sometimes square lids are also seen on some square openings. This lid is larger than the entrance and has rungs around it. Usually this kind of lid is metallic and very heavy.

We can imagine a square hole two feet wide, a rungs 1 to an inch wide. In order for the manhole cover to fall in, one end needs to be lifted, then rotated 30 degrees so that it is not hindered by the rung, and then the manhole cover is at a 45-degree angle to the horizon, at which point the shifted center of gravity is enough for the well to fall. Yes, there is indeed a possibility that the manhole cover will fall, but it is very unlikely.

With a little training for the person in charge of opening the manhole cover, he will not make such a mistake. From an engineering point of view, the shape of the manhole cover depends entirely on the shape of the hole it is intended to cover.