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Bearing Capacity of Composite Manhole Cover

Bearing capacity of composite Manhole Cover
In order to fundamentally solve the problem of serious theft of cast iron manhole covers for a long time, many manufacturers have developed a number of new anti-theft manhole covers from different materials. These Composite Manhole Covers are protected from theft by users because of their basic non-recycling value. With the increasing progress and successful application of composite manhole covers, users have gradually recognized and accepted.
In the past two years, the manufacturers of composite manhole covers have sprung up, and the covers of various materials have swarmed. Due to the lack of national high standards, the quality of their products has been uneven, and the hidden dangers of problems have been exposed, making the users worry. . Even users and authorities that have just had some knowledge and interest in composite manhole covers have been questioned.
In view of the above situation, we introduce and explain the composite manhole cover of different materials currently on the market.

composite manhole cover
1. Steel fiber concrete manhole cover: It is improved on the basis of concrete manhole cover. Due to the strong brittleness and insufficient strength, steel fibers with a length of 10-30mm are added to the concrete to improve the overall strength of the concrete. Because the phenomenon of chipping is serious during use, most of them are protected by a metal frame outside the manhole cover. . However, there are still defects such as insufficient capacity of the manhole cover, fragile, bulky, difficult to open, and rough in appearance. In the actual production process, many companies did not add steel fiber, and the user misplaced that the steel bar is steel fiber.
2. Magnesite manhole cover: It is a kind of manhole cover which is formed by mixing light magnesium oxide, magnesium sulphate and water in a certain ratio, and using bamboo or wave fiber as reinforcing material. Since the basic material is a crystal-shaped structure with a large amount of crystal water, it is used in the open air, and it is pulverized due to the dry weather and loss of crystal water, and finally results in no bearing capacity. In 2003, Harbin's nine-nine children fell into the well and drowned while playing on the manhole cover. The manhole cover was used at that time. When the manhole cover is just produced, the bearing capacity is high, but in use, the bearing capacity is lost due to the loss of crystal water and pulverization.
3. Recycled resin composite manhole cover (silicone plastic, nylon manhole cover) is made by using waste plastic or nylon and fly ash in a molten state for mixing and pressing. The thermoplastic manhole cover is repeatedly crushed by the vehicle when the temperature is high, and the manhole cover gradually creeps, causing the middle part of the manhole cover to continuously sink and fall off, forming a trap.
4. BMC molded manhole cover: It is made of unsaturated resin as the basic material, using 30-50mm short fiber and steel bar as reinforcing material, using calcium carbonate as filling material and pressing at a certain temperature. Since the steel bar is a metal material and the BMC is an organic material, the thermal expansion coefficient of the BMC is twice that of the steel bar, and the interface of the BMC is not firmly bonded when the steel plate is rusted. When the temperature changes, the steel bar and the BMC material are changed. The interface will form stress, and the repeated rolling of the vehicle will cause the steel bar to separate from the BMC interface, and finally the cover will lose its bearing capacity. And the surface is a mixture of BMC and calcium carbonate materials, and thus the wear resistance is poor.
5. Glass fiber reinforced composite manhole cover: The structure of the bottom of the glass is adopted from the structure (uniform bearing). Compared with the ribbed type (concentrated bearing), the area of the bottom is increased by several times. Secondly, the multi-layer reinforced, The layers are interlocked and the force is even. Therefore, the product has stronger bearing capacity. From the material aspect, the wear layer adopts multi-color quartz sand as the wear-resistant material and adds stabilizer to make the service life of the product double. Improved; the use of a continuous reinforcing fiber skeleton ensures high load carrying capacity of the product, while other composite covers require no fiber reinforcement, even with fiber reinforcement, which uses short fibers (the strength of short fibers is only 20%-30% of continuous fibers). When the strength is not enough, it has to be compensated by steel bars. The whole material of the product is organic material. Different reinforcing materials are used in different parts of the manhole cover, which avoids the separation and shedding phenomenon of other composite materials due to the use of reinforcing materials such as steel bars. The layered composite process is adopted to meet the requirements of institutional innovation and material innovation, and different reinforcing materials are used in different parts of the manhole cover to separate and fall off the different parts of the manhole cover using different reinforcing materials.

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