What is the problem of independent enrollment Why is the manhole cover round ?

The first weekend after the college entrance examination is known as the "Independent Enrollment Week" It is reported that more than 70 colleges and universities across the country have set their independent enrollment time for June 10 and 11. The independent enrollment topic of a university is actually a question like "why is the manhole cover round".

A candidate majoring in physics said that he was tested in the interview for three topics, all of which tested the relevance of students' professional knowledge to social applications. For example, ask what to pay attention to when a carrier-based aircraft takes off, wave-particle duality in particle physics, and how semiconductors and insulators conduct electricity together.

A candidate who applied for the journalism major said that this year's self-recruited written examination for this major is subject to two essay questions, one is 800 words, accounting for 70 points, and the other is 400 words, accounting for 30 points. In addition to asking questions about hobbies, the interview examiner also impressed her with questions such as "what is the relationship between the blackboard and the toilet" and "why are the manhole covers round".

Shandong University, Ocean University of China, and China University of Petroleum (East China) have all set the exam time for June 11. Shandong University of Finance and Economics also started the comprehensive evaluation enrollment on this day, and many candidates continued to rush on the way to catch the exam after the college entrance examination.

Candidates who are admitted after independent enrollment are enrolled in the same year as those who are admitted to the college entrance examination, and their classmates graduate, and the tuition and accommodation are the same when they are enrolled. The independent enrollment examination is a pilot to further improve the diversified selection mechanism of higher education, and is an integral part of the college entrance examination. After entering the school, students will be treated the same as those of the unified admissions

The main reasons why the manhole cover is round are:

1. After the circular manhole cover is stressed, it will spread pressure to the surroundings, and it is not easy to fragment and collapse due to uniform diffusion.

2. Due to the uneven force, the probability of fragmentation of rectangular manhole cover is much greater than that of a circular one. Therefore, in terms of durability, it is still suitable for round manhole covers.

3. This can ensure that the size of the manhole cover in any direction is larger than the wellhead. In the urban road administration, the circle is generally used, because the circular manhole cover is not easy to tilt, which can better protect the safety of pedestrians and vehicles.

4. Relative saving of the cost of generating materials, compared with rectangles or squares, the area of rectangular inscribed circles is the smallest, and the materials used for generation are also less.

5. Good transportation and construction, rolling up can be moved, urban standard drainage manhole cover weighs dozens of kilograms, and at least several adult men need to act at the same time when handling.

National standard for manhole covers.

There are many kinds of national standards for manhole covers in China, single-layer, double-layer, cast iron, ductile iron, composite, cement, magnesite and so on. According to the latest national standard GB T 23858-2009 latest standard requirements.

The manhole cover load capacity can be divided into the following types: The manhole cover load capacity and the ability of the manhole cover to pass through the vehicle are not a concept.

The manhole cover load capacity refers to the pressure test carried out by a pressure testing machine within the unit area, usually weighing 40 tons. In the case of a passing vehicle, the calculation formula for a 5-axle heavy-duty truck is: 5 axles x 40 tons = 200 tons.

With a gross weight of 200t tonnage, this heavy-duty manhole cover can be guaranteed to pass.

1.The manhole cover is heavier, and the round one is easy to move.

2.As long as the round one is put on, there will be no wrong cover, and the alignment should not be considered.

3.The round object is subjected to a uniform force.

4.Sewer access holes should leave enough space for one person to pass through, and the cross-section of a person climbing down a ladder is basically round.

5.No matter how you spin, you won't fall.

6.From the point of view of making abrasives, it is easier to make round ones.

7.Tools can be rotated by themselves in a circular well, but not others8for the mouth of the hole is round.

9.When people are accustomed to round manhole covers, it is difficult to change.

The manhole cover is round because the round manhole cover is not easy to tilt forward, which can better protect the safety of pedestrians and vehicles. The manhole cover is also square, but most of them are still round, mainly considering that the length of each diameter of the round manhole cover through its circle center is the same, so that when the manhole cover is rolled up by the passing vehicle, its diameter will be slightly wider than the wellhead below, and the manhole cover will not fall into the wellhead.

1. First of all, this involves the practical application of circles and squares (including squares, rectangles, diamonds and other quadrilaterals) on manhole covers. There are vehicles and pedestrians passing by on the manhole cover at any time, and the use of the circle, mainly considering that the length of each diameter of the circular manhole cover through its circle center is the same, so that if the manhole cover is rolled up by the passing vehicle, because no matter how it is rolled, its diameter will be slightly wider than the wellhead below, and the manhole cover will not fall into the wellhead.

2. If the square is adopted, because the diagonal of the square is obviously longer than the length of each side, when the manhole cover is rolled up, it is easy to fall into the well along the diagonal direction of the wellhead, causing potential safety hazards. Some people may ask, if the wellhead is made round or significantly smaller than the manhole cover, the square manhole cover will not fall into the well.

3. This involves the issue of maximizing the utilization and saving of materials. The use of the wellhead depends on the size of the wellhead, if you have to press the square manhole cover with an area far greater than the wellhead, then the utilization and practical value of the material are naturally not more effective than the direct use of the round manhole cover, which not only saves the material of the manhole cover, but also ensures the safety of the wellhead.

4. Because the manhole sometimes needs to be manually combed or wired, etc., the area of the manhole is required to be as large as possible. In these figures, when their circumferences are equal, the circle has the largest area. At the same time, the round shape also fits our body shape, making it easy for staff to get in and out.

5. The side of the triangle or square is composed of straight line segments, and the corners are sharp, which can easily cause injury if touched during repair. The edge of the circle is an arc, so this problem does not occur. The reason why the cover of the sewer is round is the requirement of the structural force.

Use the knowledge of circles to explain why manhole covers are round, and most of them are round, mainly because of its safety and cost saving. The circular diameter is fixed, with fixed width, when the round manhole cover is rented to the wellhead, no matter how it is placed, it will not fall. And the circular force is uniform, can bear the load from the uncertain direction, when the wheel pressure comes, the manhole cover is still flat, can better protect the safety of pedestrians and vehicles.

In the countryside and cable wells, the square shape is generally used, so that the omen can better prevent the entry of rainwater and other liquids.

The original complex causes of the circle are as follows:

First, the manhole is set up on Dabai Road, and people walk every day

It is necessary to pay attention to the safety of the walkers, and Gai'er must not fall into the manhole. If it is designed as a triangle or square, although the Gaier is larger than the manhole mouth, there is still a possibility of falling. And if it is round, since the diameter of the circle is equal, as long as the lid is a little larger, it will not fall.

Because buckets have been round since ancient times.

Let's reduce the force point, after all, people come and go.