Why is the manhole cover on the ground round?

1, because no matter how you turn it, it is round and will not fall down because of which side is narrower.

2, convenient transportation, you can roll around.

3, saving materials, the same large area, using less materials.

4. Bypassing the sewer can reduce the chances of irregular objects (bicycles, stones, etc.). ) The stolen cover fell after being stolen.

5. Roundness can reduce the possibility of pedestrians falling down after looking at the sewer cover, because women are round, their eyes are round, and the sewer mouth is round, which can reduce eye fatigue and physical fatigue caused by uneven stress on their eyes due to looking at objects with other shapes, thus reducing the possibility of falling into the sewer.

Extended data:

Well covers are used to cover roads or deep wells at home to prevent people or things from falling. According to the material, it can be divided into metal manhole cover, high-strength fiber cement concrete manhole cover and resin manhole cover. Generally use a circle. Can be used in green belts, sidewalks, motor vehicles, docks, alleys and so on.

I. Performance characteristics

1, high strength: magnesite test, high compressive strength, bending strength and impact strength, and good toughness. After long-term use, the manhole cover will not be crushed and damaged, and the "urban black hole" accident can be completely eliminated.

2. Beauty: the surface pattern of magnesite manhole cover is beautifully designed, with bright and adjustable colors, beautifying the urban environment.

3. Easy to use and light in weight: the weight of the product is only about one third of that of cast iron, which is convenient for transportation, installation and emergency repair, and greatly reduces the labor intensity.

4, anti-theft: magnesite manhole cover has no recycling value and is naturally anti-theft; According to the needs of customers, it is equipped with a locking structure to realize the anti-theft of property in the well.

5. Strong weatherability: Through scientific formula, advanced technology and perfect technical equipment, the magnesite manhole cover can be used normally at -50℃ ~+300℃.

6, acid and alkali resistance, corrosion resistance, wear resistance, vehicle crushing resistance, long service life.

Second, through the shape distinction

Generally divided into round and square.

In urban road management, circular manhole covers are generally used because they are not easy to tilt and can better protect the safety of pedestrians and vehicles.

In rural areas and cable wells, they are generally square, which can better prevent rainwater and other liquids from entering.

Third, the China standard.

There are many national standards for manhole covers in China, including single layer, double layer, cast iron, ductile iron, composite, cement, magnesite and so on.

According to the latest national standard GB/T 23858-2009, the bearing capacity of manhole covers can be divided into the following categories:

One of them shows that the bearing capacity of manhole cover and the ability of manhole cover to pass through vehicles are not the same concept.

The bearing capacity of manhole cover refers to the pressure test conducted by a pressure testing machine in a unit area, usually 40 tons. And if it is by car, the calculation formula of 5-axle heavy truck is: 5-axle x40 tons =200 tons. Under the gross vehicle weight of 200 tons, the heavy manhole cover can be guaranteed to pass.

However, some manufacturers said that if the technical parameters of 80-ton vehicles are divided by 5 axles, the manhole cover load produced by their factory is 80t/5= 16t, which means that the manhole cover load itself is only 16t.

According to item 4 of GB/T23858-2009, manhole covers are divided into six grades according to their bearing capacity:

Group 1: (the minimum type is A 15): green belts, sidewalks and other areas where motor vehicles are prohibited from entering.

Group II: (minimum type is B 125): sidewalks, non-motor vehicle lanes, car parking lots and underground parking lots.

Group III: (C250 type is the lowest choice): residential quarters, back streets and alleys, areas where only light motor vehicles or automobiles drive, and within 0.5m of kerbs on both sides of roads.

Group IV: (D400 type lowest): urban trunk roads, expressways, high-grade highways, expressways and other areas.

Group V: (minimum E600 type): freight stations, docks, airports and other areas.

Group VI: (minimum F900 type): airport runways and other areas.

References:

Baidu encyclopedia-manhole cover