Why are sewer manholes round? Why is the manhole cover round. Cause and effect

Round? And what else can they be? Theoretically, the hatch can be square or rectangular. But such a design, rather, is an exception to the rule. The hatch is not a simple manhole, it must be securely closed. It should be easy to maintain and safe to operate.

If convenience is an amateur, then reliability at the level of standard loads can be ensured precisely by the round design of the cover. The configuration of the base, which, in fact, is a sewer hatch, depends on its shape.

Waste system

Sewer networks are a complex of structures designed to collect and divert from users to treatment facilities. The easiest way to do this is to dig a trench, lay pipes in it, through which drains will be discharged.

To be able to service the system after a certain distance, inspection shafts are required. In the conditions of urban infrastructure with dense buildings, it is possible to conduct sewer networks only along roads or directly under them. In this case, with heavy traffic, the hatches must be securely closed. But why are sewer manholes round? They must have sufficient strength to withstand the maximum possible traffic loads.

In a large city, the number of inspection hatches and all kinds of mines can be in the hundreds of thousands. After all, this is not only sewerage, it is also a network of communications: water supply, heating networks, electricity, gas, telephony, and so on.

Manholes

For ease of access to communications, the well shaft is usually made in a round shape. Sewer rings used for the construction of such structures are most often made of reinforced concrete.

The cylindrical shape of the well is most suitable for maintenance. It is more convenient to work in such mines. They are suitable for ventilation, as the air circulation in a cylindrical object is more intensive.

The cover size, base area and internal diameter are selected in accordance with the purpose of the inspection shaft. In this case, all elements of the system will correspond to each other as much as possible. The location, possible loads, traffic intensity are taken into account.

It depends on the shape of the lid. On the one hand, maintenance personnel must have easy access to underground utilities. On the other hand, the well must be securely closed to exclude the possibility of foreign objects getting inside, to ensure the safe movement of pedestrians and vehicles. A round lid is best suited for this, which means that the hatch itself should be of this shape.

Depending on the purpose, they are divided according to the type of communications laid under them: engineering cable networks, water supply, gas mains, heating mains, storm and sewerage. The size of the sewer hatch in different countries different. In Russia, standard dimensions are most often used (645 and 800 mm). Hatches that are not manufactured in accordance with GOST are designed and developed by manufacturers in accordance with the order and specific technical conditions.

This configuration has a number of advantages. Previously hatches were made various shapes. They could be square, rectangular, oval, and even triangular to indicate the direction of water flow. However round form The cover turned out to be the most suitable.

She will never fall into the well, no matter how she is turned. A round lid is easier to open, so the point of application of force in any place of the circle will be the same. It can be rolled by placing it on edge. In the manufacture of such a design is economically more profitable.

The round shape of the lid is less prone to sagging. It withstands a large load with the same thickness, which means that it can be made thinner without losing quality. In the production of round castings, they give a smaller percentage of rejects (shells, pores, cavities).

Material

The base and manhole covers for those in charge are most often made of cast iron. This material has strength, which makes it possible to withstand heavy loads, and corrosion resistance for a long time. The weight of the structures is sufficient so that passing vehicles cannot accidentally lift and move the cover. are made during the remelting of secondary raw materials, they are cheaper than steel counterparts.

In places where there is no heavy traffic, it is not advisable to install heavy and powerful structures. Recently, hatches made of plastic, polymers and composite material have appeared. They are lighter, cheaper, have a sufficient margin of safety, long service life.

In private houses, reinforced concrete sewer rings are used to equip sewage, manholes and septic tanks. In this case, it is quite justified to install the same base for the hatch on top of them. The cover is also made of concrete. It is made of a larger diameter, does not enter the groove, but simply covers the hatch opening. The massive structure is heavy enough that it cannot be accidentally moved. This provides the necessary safety during operation.

Specification and marking

For increased loads on the roads, heavy hatches (class T) are used. They may have a weight of over 100 kg and a thickness of over 100 mm. Where vehicular traffic is not provided, light hatches (class L) are used. Constructions for the garden, lawn and other areas (class A) have a diameter of 540 mm and a thickness of 50 mm.

Why are sewer manholes round and marked? This is done for the convenience of recognizing their affiliation. On their covers there are letters: GS - gas network, MG - main gas pipeline, PG - fire hydrant, etc.

The text of the work is placed without images and formulas.
Full version work is available in the "Files of work" tab in PDF format

1. Introduction

When our house was being built, they laid water and made a well, which was then covered with a special manhole cover. I noticed that in our city there are round lids everywhere: in our yard, on the roads, and near the school.

And then I became interested in why the manhole covers are round. appeared before me problem: there are many geometric shapes, and sewer manholes are made round for some reason and perhaps there is some other figure suitable for manholes.

TARGET: defining wheel properties that are used in manhole covers.

TASKS:

1. Get acquainted with the new properties of the circle for me and, with the help of experiments, establish the simplest connections and draw conclusions.

2. Search for material about others geometric shapes, which could be used by man in the manufacture of manhole covers.

3. Show the possibility of using circles (and if there is a figure similar in properties) in life.

Hypothesis: in addition to the circle, there are shapes that can be used to make manhole covers.

Research methods

1. Conducting a survey “Why are manhole covers round?”.

2. Search for materials on the Internet.

3. Observations.

4. Conducting experiments.

2. MAIN PART

I asked my parents, classmates and acquaintances my question and got different answers. Most people think that it is so convenient - it is easier to climb into a round hole, several answers were beautiful, and some answered that they did not know. Then I started looking for information on the Internet.

Experience 1. Round objects are easier to move - they can simply be rolled. While objects of rectangular and triangular shape interfere with the corners. And manhole covers are made even more heavy - they are made of cast iron. Then we can conclude that a round heavy cover can be moved by one person. A hatch of a different shape will have to be carried in several hands.

Experience 2. The round manhole cover will never fall into the well, which means it is best suited for performing a protective function. All this is because the diameter of the lid is always larger than the diameter of the well itself. And other figures can fail (for example, at an angle).

Experience 3. Draw two parallel tangent lines and fix the distance between them. Let's start spinning the circle. He constantly touches these lines and one can say that a closed curve (a circle that describes a circle) has a constant width. This is also a property of a circle. And it is taken into account in the manufacture of manhole covers - less likely to make mistakes in production.

Experience 4. Used in the manufacture of round lids less material and reduce their cost.

Here are the reasons why manhole covers are round. But I am interested in one more question: is there a figure similar in properties to a circle. And here the program that I watch - "Galileo" helped me. From it I learned that there is a figure similar in properties to a circle. This is the Reuleaux triangle. It was studied by the German scientist Franz Rehlo in the 19th century. Let's check this out too.

Experience 5. The Reuleaux triangle is a figure that has a constant width. We draw two tangent straight lines, fix their width and begin to rotate the Reuleaux triangle. And always one point, located in one of the "corners" of the Reuleaux triangle, and the other on the opposite arc of the circle, will touch the lines. Experience 6. An object made in the shape of a Reuleaux triangle can roll. Let's install a plank on 2 cylinders in the form of these triangles and see that it rolls.

Experience 7. Reuleaux's triangle, if placed on a manhole, will not fail either. I made such a layout and I suggest you check it out.

3. CONCLUSION

After doing the work, I was able to conclude that the hypothesis put forward by me - in addition to the circle, there are figures that can be used to make manhole covers, was confirmed. But it is easier to make round lids - there is less chance of making a mistake and, therefore, they are made. And now I can answer a question that is often asked when applying for a job at Microsoft. Here are the answers: safety, ease of movement, lower cost, fewer errors in their manufacture.

And I also learned a lot Interesting Facts.

1. When racing cars are held on city streets, the covers are welded to the hatches. When driving race cars, their aerodynamic characteristics create such low air pressure between the road and the bottom of the car that it is enough to lift the lid of the sewer manhole.

2. In the early 2000s, a large art project “Sewerage of all countries, unite!” was held in Moscow. - where photographs of sewer manholes from around the world were presented.

4. LIST OF LITERATURE AND RESOURCES

1.http://www.etudes.ru/ru/etudes/mazda

2.http://otvetprost.com/387-pochemu-lyuki-kruglye.html

3.http://expirience.ru/pochemu-lyuki-kruglye/

4. Recording of the program "Galileo" from May 2012.

Many have faced the question of why sewer manholes have a round shape. Most have heard it in job interviews. In this way, "insidious" HR managers test the general erudition and ability for creative thinking of potential employees.

Also often this question is used in various competitions and quizzes. If you study the device of sewer manholes, then the answer to the question will become obvious and quite understandable. This is what we'll do.

Manhole device

A sewer well usually consists of a shaft and a working room, and the hatch serves as a cover. The working room is equipped and arranged depending on the type of serviced communications and the requirements for their operation. The depth of the shaft and the size of the room also depend on this.

• Usually the height of the room is 1.8 meters, but it can be more or less. The main criterion for its determination is the depth of communications. The length of the shaft directly depends on the depth of the room. Usually the mine is round and 0.7 meters in diameter. There must be a ladder in the mine so that the worker can go down to the room. The material for the construction of the mine is usually brick or concrete.
• The cover on the sewer manhole is necessary to prevent foreign objects and people from entering the mine. The round shape prevents the cover from falling into the shaft if someone steps on it, which means it protects against accidents. This is the main reason why the shape of sewer manholes is made round.
• Also, the covers have a fairly large mass, and sometimes this also raises questions. This fact can also be easily explained. Very often, sewer manholes are located on the roadway and when the car wheels are moving, they fall on the cover. If the cover were light, it would easily turn over, opening the shaft and creating the possibility of accidents. To avoid this, the covers are cast from cast iron, which is considered one of the most heavy metals.
• On the surface of the lid, there are usually raised stripes, letters, or other patterns and images. This is also not done by chance. The ribbed surface prevents slipping and increases the adhesion strength of car tires and pedestrian soles to the surface of the sunroof. There are flat covers, and there are ones that are curved in the middle, but you will never find those that are concave inside.

On the wells of cable ducts, two covers are usually located at once - protective and locking.

The protective one is on top. A lock is additionally located on the locking cover, which prevents unauthorized persons from entering the shaft in order to steal the cable. These lids are lighter than conventional lids because they are made of steel.

Also, sewer hatches can be installed in gas, thermal, water and other wells. engineering networks and storm sewers.

Each one is designed to ensure that none stranger or the animal accidentally or deliberately did not enter the sewer well, mine and did not get unhindered access to underground utilities.

Varieties of sewer manholes

Sewer hatches can be divided into several types depending on the design, the material from which the hatch is made, and the type of communications that it closes. Sewer hatches can close drainage systems, cable (electrical or telephone), storm drain systems.

Depending on the material used in the manufacture, cast iron, plastic, composite, concrete, reinforced concrete and rubber manholes, as well as manholes made of a polymer-sand mixture, can be distinguished.

Helpful information ! Each material has its pros and cons, taking into account which you can choose best option for a specific situation. But anyway traditional option is a manhole made of gray or ductile iron. This material has high strength, is resistant to mechanical stress of various nature, is independent of weather conditions, and its service life exceeds the shelf life of all other materials.

Manhole safety

The main purpose of giving the sewer manhole a round shape is to ensure the safety of the population. Unfortunately, cases of an adult or child falling into an open sewer shaft are not uncommon. If the mine is shallow, then this can result in one or more fractures, but a great depth can even threaten death.

A common cause of such falls is the theft of a manhole cover.

Now many people, walking down the street, are distracted by talking on a mobile phone or writing SMS messages, sometimes getting so carried away that they forget to look under their feet. This distraction leads to accidents.

Also, a car can get into an open hatch, which at best will lead to minor damage to the car, and at worst, to injury to passengers. Fans of riding other modes of transport are also in danger - scooters, motorcycles, mopeds, bicycles, roller skates or skateboards. Hitting the hatch at high speed is fraught with serious injury.

Fun Facts About Manholes

If the sewer hatch was installed a long time ago, then opening it can be a serious problem. In this case, specialists weld a metal handle to the hatch from above, open the hatch, perform the necessary operations, close it, and then cut off the handle.

Also, hatches with existing holes have long been launched into production, into which a hook can be inserted and thus the cover pulled out.

But such hatches cannot be used when closing electrical, telephone and cable networks. This is due to the fact that water can get into the holes due to rain or snow melt, which can damage the networks and adversely affect the operation of the entire system.

The issue of the excess mass of sewer manholes should also be explained.

This weight is given to the lids specifically to make it difficult and sometimes prevent their theft. The fact is that free metal has always attracted fans to profit at the expense of the state. Thus, in the last decade of the 20th century in the territory Soviet Union several thousand manhole covers were stolen. Thieves rented them for scrap, thereby earning substantial money.

Helpful information! To avoid theft, currently used wooden shields, plastic hatches or concrete circles, which cover the main cover from above. Covers fastened with metal hinges have also become widespread. They cannot be simply removed and carried away; special equipment will have to be used, which will complicate the process of theft.

Also, the hatches are made so massive that teenagers do not play games in the sewers or use them for other, less decent things.

There are several other explanations for why sewer manholes are round.

• Firstly, this form facilitates transportation. The hatches are heavy enough to carry the cover, for example, square shape you need to use the power of one or even two adult men. The round lid can be easily rolled on the ground by any teenager and for any distance.
• Secondly, there are no problems when installing the cover. It is unlikely that anyone will have questions about its location in the hatch of the well. The only mistake here may be to install it on the wrong side up, but this is not very critical for operation.
• Well, and thirdly, less material is used for the production of round products.

The eternal question: "Why is the hatch round?"

Almost all hatches in the city are covered with special round covers. If you carefully study such objects, it turns out that they are the same all over the world. This involuntarily leads to the question: “Why are manhole covers round? Why do the technical objects themselves have exactly this shape, and, for example, not square? It turns out that the answers lie on the surface.

Some details about sewer manholes

The described items are made of cast iron or concrete. They are specially made heavy and unbearable so that no one would have a desire to take a “useful” thing with them. It is not so easy to open a technical hole on your own, and this is specially provided for in the design for the safety of passers-by.

Sewer hatches have a conditional classification. They are divided according to the material of manufacture and the type of communications passing under the trigger shafts. Therefore, experts distinguish:

1. Drainage systems.
2. Storm sewers.
3. Electrical networks.

Manholes are produced from high-strength cast iron and plastic, a special polymer-sand mixture, composite materials and reinforced concrete. But they are all invariably round in shape. Why, let's find out.

Logical explanation

So why is the manhole round? The described technical object consists of several parts - a round shaft, an observation room and a cover.

The observation room may different shape. It all depends on what communications are laid in the well. Dimensions are chosen taking into account the convenience of their maintenance. But the mines are invariably made round. The diameter of the oval is 0.7 meters. They are assembled from bricks and equipped with an additional ladder, which helps the service worker to descend unhindered.

From above, such a hatch must be closed with a lid. It prevents various kinds of third-party objects from entering the sewer systems that can provoke the occurrence of accidents. Almost everywhere the lid has a round shape. Why not square? Because in any position, such a cover will never fall in and hit the person there.

A square cover under the influence of vehicles can easily fall inward, slipping there at an angle. After all, the diagonal of a square is always greater than any of its sides. A circle has the same radius, no matter how you twist it.

Typically, manufacturers make lids that weigh more than 50 kg. This is done so that no heavy flow of cars could move them.

Other explanations for the shape of hatches

It is very rare to find such a form.

There are a few more explanations to help understand why manhole covers are round:

• Firstly, the ratio of the cross-sectional area to the circumference of a circle is greater than that of a square or rectangle. This makes it possible to reduce material costs during the production of caps and save on the production of products.
• Secondly, the round shape reduces the internal forces that invariably arise when any cover is placed on an object. And this also provides savings in the production of the product, since in this case it is possible to produce covers of a smaller thickness.
• Thirdly, the round shape helps to reduce the production of defective products. By reducing the number of support lengths, the likelihood of errors leading to the appearance of uneven protrusions and other characteristic defects is reduced.

And further. The round lid is much easier to transport for one person. He can just roll it to the place. And a square or rectangular one will have to be carried in several hands.

The above arguments show that the choice of form is explained by elementary practicality.

Interesting facts

In the world, cases of using caps of a different shape are known. So, for example, in the American city of Nashua, you can still see sewer wells covered with triangular covers. Their acute angles indicate the direction of the flow Wastewater, and this, until recently, helped repair teams to navigate well. But today their use is recognized as unsafe, so the prefecture dismantles them and replaces the triangles with circles.

There are also other forms

Now you know why sewer manholes are made round. But why they are made so massive and heavy is also an interesting question. Although the explanation lies on the surface. Weight provides relative safety from theft and delivery of the described products to metal collection points. About 10 years ago, a wave of characteristic crimes swept across the country. The covers began to disappear en masse, then the designers came up with an interesting solution.

Most modern sewer wells not just covered from above with a massive object, which one person is not able to carry away. The lids were put on strong hinges, and they turned into real doors, which are additionally locked.

It is impossible to leave the wells open, especially those in which storm sewer and plumbing. Their depth sometimes reaches 6 meters, and at the bottom technical room a lot of protruding pipes and pieces of fittings. If a person in the dark falls there, the case will end in death. Therefore, those who are responsible for sewer manholes - and this is the district administration - have a great responsibility for the safe use of this technical structure.

Who else can be responsible for hatches?

But the Russian people are still accustomed to seeing such a hatch

There are wells that are not in municipal ownership, but belong to the property apartment building or to the property of a particular legal entity.

All ownerless objects are first registered by the body that registers the right to property. This happens at the request of the local government. Then, through the court, everyone can challenge their own right. If there are no applicants for a year, all ownerless objects are transferred to the departments of specialized companies.

Generalization on the topic

The round shape of sewer manholes is more practical than all other varieties. Many years of operation of sewer facilities have proven that round holes are more technologically advanced and have a longer service life. And all because such a hatch is more resistant to temperature extremes.

Hello always dear friend!

There is a type of question that is considered to be a quick wits question. Sometimes this is true. But more often such questions are asked with several goals at once.Why hatches are round interview question just from this series. Although it is becoming less and less common, because it has already lost its former originality and the effect of surprise.

Let's remember that at the interview they want to evaluate not so much "Who are you?", but "What are you?".

1. How would you respond to this question? - the first goal of your interlocutor.

He wants to understand the degree of your emotional maturity.

2. Will you look for an answer to this question? is the second goal.

Let's remember that the employer is interested in several questions that he never asks directly. One of them: will you solve the problems that will inevitably arise in the course of your work.

Or you will look for reasons why the problem cannot be solved, or you will transfer problems to other people, including the manager.

3. The content of the response itself is the third goal.

Will you be able to solve problems that require intelligence and analytical thinking, logic?

If you say “I don’t know” or “I find it difficult to answer” instead of answering, this means that when faced with a difficult task, you are likely to save.

How to react?

Let's agree right away that we define this question “why the hatches are round” as, and not manipulative and not. Therefore, we respond constructively.

The worst thing you can do is puff out your cheeks and freeze something like this:

“Listen, what does this have to do with the subject of our meeting?”

After that, consider that you did not pass the test, although in fact you are right. The reason is that you did not accept the rules of the game that are offered to you. Again, this question is constructive and is not an attack on your personality. Therefore, it should be answered constructively.

Let's remember the principles of answering constructive interview questions:

1. If you are asked questions, that's good. If you are not asked anything, how will they know that you are the best applicant?
2. As a consequence of point number 1: Just give the interlocutor the right to ask any questions. Any question is your opportunity to be better than other candidates. You will answer confidently and calmly, and there is no reason to be afraid and nervous.
3. Majority are asked to get to know you better, not to hear the correct answer. That's what you came here for, so they know what a great candidate you are.

How to answer?

1. Listen to the end.
2. Verbal reaction - and with the tips of the lips (teeth closed!), A slight nod.
3. A small pause.
4. Answer.

The most simple and logical answer to this question is:

Round hatch - cannot fall into the well. No matter how hard you try and twist it. The square one has a diagonal longer than its sides, and when raised, it can slide down into the well. Drown or even injure someone. Besides -the diameter of the top of the round manhole is usually larger than the bottom, and it cannot slide in under any circumstances.

In addition, round hatches are more convenient to move - it can be rolled.

A couple more questions from the same series

About the cake

Himself Question: How to divide the cake into eight identical pieces using 3 cuts?

Answer: First, you should make a cross-to-cross cut, thereby dividing the cake into 4 equal parts. Next, make one cut horizontally in half along the entire diameter. The pieces turned out lower, but the problem is solved - you have 8 equal pieces.

The second option: after your two cuts, we have 4 pieces. We can put them on top of each other. Then divide all four pieces in half with one cut.

About light bulbs

There are three light bulbs in the room. There are three switches in the corridor leading to the room.

Question: How many times does the door need to be opened to determine which light corresponds to which switch?

Answer: It is enough to open the door once. We turn on 2 switches at the same time, then turn off one. We enter the room: we see that one lamp is on. It's from the first switch. Place your palm on each of the remaining two bulbs. Which is warm - the one from the second switch, respectively, cold from the third.

In the event that, if any intelligible answer does not come to mind, start thinking out loud. Trying to find the right one is much better than a nervous reaction or a “difficult to answer” response. Keep in mind that some of these questions do not have a clear answer at all.

Your attempts to find an answer, a train of thought, solutions are often more important than the answer itself.

Thank you for your interest in the article. I would appreciate a comment (at the bottom of the page).

Subscribe to blog updates (the form under the social media buttons) and receive articles on topics of your choice to your mail.

Have a nice day and good mood!