On July 6, a Nanjing citizen complained that there was a strange manhole cover beside Xianlin Avenue in Nanjing Xianlin University Town. The cover was "as thin as paper", only 0.7 cm at the thinnest point, and the manhole with a big mouth was about 3 meters deep, posing great security risks. The head of the local management committee said that the manhole cover is made of plastic and lined with thin steel bars, but there should be no problem for pedestrians. The committee then ordered someone to transport a cement manhole cover to cover it. (Xinhua, July 7)

The release of the "paper manhole cover" immediately triggered criticism from netizens. The thin manhole cover ignored the safety of pedestrians and became a "trap". Some netizens also speculated that there are moths that harm the country and the people, and they ate rebates in municipal bidding and procurement. Industry insiders said that when bidding for relevant projects involving manhole covers, the selection of manhole covers must be carried out according to national standards, otherwise they will not be eligible to participate in the bidding. In addition, construction units must take out materials for compression tests and entrust third-party testing institutions to inspect them, and products that pass the inspection can only be used. During the installation process, the supervision unit will also supervise the quality of the manhole cover, and the unqualified quality will be stopped immediately. Now, the "paper manhole cover" has been presumed to be a problem product with unqualified quality, and the netizens' judgment is based on just seeing a few photos.

In the network, many times may not be the picture has the truth. People are used to seeing manhole covers made of metal or cement, and when they see plastic manhole covers, they call them "weird". In fact, with the rapid development of science and technology, human understanding of material technology is not the Bronze Age, can not always hold the traditional old concept that only reinforced cement manhole cover is qualified. In line with national standards, in addition to metal manhole covers and cement manhole covers, there are also unsaturated resin-based manhole covers and recycled plastic coal ash composite manhole covers. According to the "Urban Construction Industry Standard CJ/T121-2000" implemented by the Ministry of Housing and Urban-Rural Development in 2001, the definition of the recycled resin composite manhole cover is: the material formed by the physicochemical action of additives under certain temperature and pressure conditions with thermoplastic resin and coal ash as the main raw materials. In 2005, the Ministry of Housing and Construction issued a new industry standard for the inspection of the manhole cover with polymer matrix composite materials. The main raw material sources can also be replaced by various waste polymers and waste particles and fibers. Speaking of which, some people will be surprised that manhole covers can not only be made of plastic, but also be made of discarded garbage. As can be seen from national standards, manhole covers made of plastic do not mean cutting corners.

Traditional cast iron manhole covers have strong carrying capacity, are durable and relatively stable in quality, but they are frequently stolen because of their recycling value. We often see such news that the manhole covers have been stolen overnight on the roads that have just been built and put into use. If not replaced in time, it will also cause safety hazards to vehicles and pedestrians. Many cities stipulate that manhole covers must be repaired within 24 hours after they are damaged or lost, or they will be held accountable. But who can guarantee that there will be no accidents during the vacuum period without manhole covers? What's more, some wellhead standards are different, when a certain manhole cover is lost and in urgent need of replacement installation, it is often difficult to find a fully matched product, even if it is barely made up, it is also due to the phenomenon of driving beating, manhole cover clamshell injury and destruction of the car, defective manhole cover noise nuisance. The problem of the theft of the traditional cast iron manhole cover in the process of use depends on the development of the social and economic level and the improvement of the level of civic morality, which is by no means a complete solution overnight. And plastic and other composite manhole covers because there is no recycling value, reduce the chance of theft, if the quality meets the national standard, but is the safest.

Nanjing "thin as paper" manhole cover in the end whether there are quality problems or corruption problems, but also need to be investigated by relevant departments. If you open the manhole cover, even if there is really a problem behind it, you should not give up eating for fear of choking and deny the value of plastic manhole covers. I noticed that this "paper manhole cover" is not on a driveway or sidewalk, but on a green lawn, and people should not step on the lawn at will. In some occasions where the load-bearing capacity of manhole covers is not too strong, can we introduce new manhole covers with new materials? At present, China is building a conservation-oriented society and vigorously developing a circular economy. This is not only a slogan, but also the implementation of frequent replacement of metal manhole covers in details such as "manhole covers", which consumes human cost and natural resources. Correspondingly, the new manhole covers can turn waste into treasure. What needs to be done now is to strictly control the quality of the new manhole cover and convince the public to accept new things with inexpensive and high-quality products.

Wen/Pujia

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