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 load capacity of manhole covers can be divided into the following categories: one point is that the load capacity of manhole covers and the ability of manhole covers to pass through vehicles are not the same concept. The load capacity of the manhole cover refers to the pressure test conducted by a pressure testing machine within a unit area, usually weighing 40 tons. If it is through a vehicle, the calculation formula for a 5-axle heavy-duty truck is: 5-axle x 40 tons=200 tons. At a total weight of 200T, the heavy-duty manhole cover can ensure passage.