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. ?
From 2065438 to March 2009, the manhole cover monitoring system independently developed by 203 Aerospace Science and Technology Institute came out? .
key property
technical parameter
Test load of technical parameters: heavy-duty 400KN, ordinary 250KN, light-duty 125KN? [ 1]?
Bending strength: average 22MPa impact strength: average 10J/m2.
Water absorption: 1%
Acid resistance: the sample is at 20%
Soak in sulfuric acid solution for 48 hours.
The surface has no corrosion, and the mass loss is 65438 0%.
operating characteristic
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.
Manhole covers standard
Chinese 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.
Japanese standard
Engineering level
1958, Japan made mandatory standards for key indicators such as thickness, material and bearing capacity of manhole covers. The current industry standard requires that the manhole cover must be cast with high-strength ductile iron, with a thickness greater than 17 cm and a weight of 40 kg.
Shou Wu Kang, director of the Presidium of Japan Ground Cover Industry Association, said that all manhole covers in Japan must pass the quality acceptance of Japan Sewerage Association and other industry organizations. You can't leave the factory until you get permission. After that, there are regular quality inspections every year, and the quality of the manhole cover is guaranteed through such a supervision mechanism.
meet a criterion
In China, most manhole covers are not closely attached to the road surface, and tires will collide with manhole covers when vehicles run over them, so manhole covers have become one of the noise sources in cities. In the 1970s, many Japanese people suffered from the noise of manhole covers, and they asked local governments to solve the "noisy manhole covers". The Japanese government immediately revised the standard of sewer manhole cover, changed the cylindrical manhole cover into a conical manhole cover with a large top and a small bottom, and required that the manhole cover casting must be accurate to millimeter. In this way, the manhole cover and the road surface can be seamlessly attached together, which not only eliminates the noise, but also increases the difficulty of stealing the manhole cover.
security issue
20 10 a sudden rainstorm in Kochi, Japan, caused some manhole covers to fall off or be damaged, causing many pedestrians to fall into the sewer. The Japanese Ministry of Homeland Security immediately convened experts and local governments to set up the "Emergency Safety Countermeasures Committee for Sewer Covers" to conduct on-the-spot investigations on the sewer sites with problems. The investigation found eight kinds of manhole cover safety problems that need to be solved. According to the principle of "according to the danger level and existing capacity, lock the dangerous area, delimit the danger level and completely eliminate the potential safety hazards", the corresponding "emergency safety countermeasures for manhole covers" were formulated.
Specifically, it includes replacing the decompression anti-falling manhole cover, setting a camera to monitor the state of the manhole cover, setting a ladder in the sewer to avoid falling pedestrians, and establishing a manhole cover information and damage monitoring system.
Management technology
guard against theft
In order to realize the effective utilization of waste resources, Japan has promulgated a series of laws and regulations, such as the Law on the Promotion of the Utilization of Renewable Resources and the Law on the Disposal of Waste, which stipulate that consumers have the obligation to seal the waste and discharge it in a classified way, and shall not throw it away illegally, and pay the fees according to the regulations. Therefore, from a legal point of view, the Japanese can not only benefit from handing over scrap metal to recycling enterprises, but also need to pay treatment fees to recycling enterprises. If thieves want to steal the manhole cover, they can only find illegal metal recyclers, and these illegal metal recyclers are often the key targets of the Japanese police.
distinguish
In Japan, most manhole covers have unique numbers and will be included in the sewer management system. Taking Tokyo as an example, Tokyo Sewage Treatment Bureau gives each manhole cover a unique number, which consists of the manhole cover type, the manhole cover identification code and the manhole cover construction date. On the one hand, it can quickly identify the damaged manhole cover, on the other hand, it can know when the manhole cover expires and should be repaired and replaced. Most manhole covers in Japan are maintained by private public utilities.
In addition, the pattern design and shape of Japanese manhole covers also vary from region to region and from department to department. The sewers managed by the municipal, district and town governments are distinguished by the city flowers, district flowers and town flowers on the manhole cover. If the manhole cover is damaged and needs maintenance, the responsible subject can be identified immediately. Individual-owned sewers will be marked with the word "private" and the owner's surname on the manhole cover to show the difference. The manhole covers of fire hydrants are mostly rectangular or engraved with cartoon patterns of firefighters.
Japan is a country with frequent natural disasters, and there are "emergency shelters" near residential areas. The manhole covers around some shelters are painted in color in addition to indicating the direction with arrows. The yellow arrow means within 200 meters from the shelter, and the red arrow means within 100 meters.
Reference source: Baidu Encyclopedia-manhole cover