The main reasons why the manhole cover is round are:
1. After the circular manhole cover is stressed, the pressure will spread to the surroundings. Due to the uniform diffusion, it is not easy to fragment and collapse.
2. Due to uneven stress, rectangular manhole covers are more likely to break than circular ones. Therefore, considering durability, round manhole covers are suitable.
3. This ensures that the size of the manhole cover is larger than the wellhead in any direction. In terms of road administration in urban areas, circular manhole covers are generally used because they are not easy to tilt and can better protect the safety of pedestrians and vehicles.
4. It is relatively economical to generate material costs. Compared with rectangles or squares, the area of ??a circle inscribed in a rectangle is the smallest, and less materials are used to generate it.
5. The round shape is easy for transportation and construction. It can be moved by rolling it. The urban standard drainage manhole cover weighs tens of kilograms. At least several adult men are required to move at the same time during transportation. Extended information
There are many national standards for manhole covers in China, including single-layer, double-layer, cast iron, ductile iron, composite, cement, magnesite, etc.
According to the latest standard requirements of the latest national standard GB/T 23858-2009,
The load capacity of manhole covers can be divided into the following types:
There is one explanation , The load capacity of the manhole cover and the ability of the manhole cover to pass vehicles are not the same concept.
The load capacity of the manhole cover refers to the pressure test performed by a pressure testing machine within a unit area, usually 40 tons in weight. And if it is a vehicle, the calculation formula for a 5-axle heavy-duty truck is: 5 axles x 40 tons = 200 tons. When the total vehicle weight is 200T, this heavy-duty manhole cover can ensure passage.
Reference: Baidu Encyclopedia-Manhole Cover