Before answering this question, we must first understand how the subway is excavated . Shield machine is a kind of professional engineering machinery for tunnel excavation, which is widely used in large-scale projects such as subways, railways, municipalities, etc. It is also known as the "king of construction machinery". For example, when it is difficult to excavate hard rocks or areas with soft soil, the shield machine can solve the problem. Its appearance has improved the efficiency of tunnel excavation by about 10 times. So how does the shield machine "eliminate" the soil?

The head of the shield machine is a circular turntable full of blades, which can dig up the soil in front of it when it is running. Part of these soils will be very firm around the tunnel, which not only reduces the cost of transporting soil, but also increases the firmness of the subway tunnel. In addition, in the process of digging the tunnel, you may also encounter caves 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, a large amount of soil with strong adhesion needs to be used to reinforce the road, so the workers will directly backfill the excavated soil on it during the operation for the subway. building. Of course, if there is any leftover soil, it will not be wasted casually.

The municipality will directly transport these soils to other cities for construction, or be put into the construction of green belts. In this way, the utilization rate of resources has also been improved. The use of this soil backfill method saves the cost of subway construction on the one hand, and on the other hand, it facilitates the work of workers and shortens the construction period. However, in order to minimize the disturbance to the residents of the surrounding cities, these transport vehicles usually work at night, so it is naturally difficult to see the soil digging the subway.

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

The external construction cost of subway is extremely expensive, and the price of one kilometer in some cities has reached 800 to 10 billion. But although the cost is expensive, the service life is long, and the maintenance is relatively simple in the later stage, so it is still worthwhile in the later stage. Take Moscow's subways, which are in their 80s and still in use after simple repairs and upgrades. If there are no geological disasters, their general lifespan can reach at least four or five hundred years. Of course, in the process, people need to constantly upgrade and transform it.