Before answering this question, we must first understand how the subway is excavated . The shield machine is a kind of professional engineering machinery for tunneling. It is widely used in large-scale projects such as subways, railways, and municipal projects. It is also known as the "King of Engineering Machinery". It plays a key role in the process of tunneling. For example, when encountering hard rocks that are difficult to excavate, or where the soil is soft, the shield machine can solve the problem. Its appearance has increased the efficiency of tunnel digging by about 10 times. So how does the shield machine "eliminate" the soil?

The head of the shield machine is a circular turntable covered with blades, which can cut open the soil in front of it during operation. Some of these soils will be very firm around the tunnel, which not only reduces the cost of transporting the soil, but also increases the firmness of the subway tunnel. In addition, in the process of excavating the tunnel, you may also encounter holes and places that need to be filled, and then the reserved soil will come into play.

In addition, in order to ensure that the subway does not collapse, it is necessary to use a large amount of highly cohesive soil to reinforce the road, so the workers will directly backfill the excavated soil to the subway during the operation. building. Of course, if there is still some excavated soil left, it will not be wasted casually.

The municipal council directly transports these soils to other urban constructions, or puts them into the construction of green belts. In this way, the utilization rate of resources has also been improved. Using this soil backfill method, on the one hand, it saves the cost of subway construction, and on the other hand, it also facilitates the work of workers and shortens the construction period. However, in order to minimize the disturbance to surrounding urban residents, these transport vehicles usually work at night, so it is naturally difficult to see the soil dug for the subway.

Having said so much, do you know how much money it takes to build a subway?

The external cost of the subway is extremely expensive, and the price of one kilometer in some cities has reached 800-1000 million. But although it is expensive, it has a long service life, and it is relatively simple to maintain in the later stage, so it is still very worthwhile in the later stage. Take the subway in Moscow as an example. Their subway is over 80 years old, and it is still in use after simple maintenance and upgrades. If there are no geological disasters, their general lifespan can reach at least four to five hundred years. Of course, in the process, people must continue to upgrade it.