Why did the subway dig so deep, but no soil was transported out? Where did the excavated soil go?

Why did the subway dig so deep, but no soil was transported out? Where did the excavated soil go?

In 20021year, Hangzhou plans to open a total subway mileage of145.98km, Guangzhou plans to open a total subway mileage of 91.15km, Wuhan 72.3km and Beijing 62.6km.. These four cities add up to a total mileage of 372 kilometers. The construction of so many subways is bound to dig up a lot of soil, but why can't people living in cities see the soil coming out of the tunnel? Where are all these dirty things?

Subway is usually built at a depth of 20 to 30 meters underground. The tunnel diameter is 7 meters on average, and the cross-sectional area is about 38 square meters. Because the subway is a two-way track, our mileage will double, and 372 kilometers will become 744 kilometers, so the soil dug up by these four cities will reach 28.272 million square meters. What is the concept of this soil quantity? The storage capacity of the West Lake is 6.5438+0.4 million square meters, and the soil can fill two West Lakes. What's the use of so much dirt?

Some of them have been used in the excavation process. There are two ways to dig a subway tunnel. The simplest and most direct method is open-cut backfilling, that is, digging a big pit in the street, building a tunnel structure underground, and paving the road again after the tunnel has enough support. In this method, except the ground is cut, other lines, meters, etc. It also needs to be resurfaced. At present, the most commonly used method is drilling and excavation, using special construction machinery shield machine for tunnel excavation and TBM full-face hard rock tunnel boring machine. Shield machine is suitable for soft soil stratum, and TBM is used for geotechnical stratum. This kind of tunnel boring machine is mostly used in places with dense buildings, which can reduce the impact of ground construction on cities and can also be used in some places with water. Shanghai Metro Line 5 crosses Huangpu River.

The drilling and excavation method, as its name implies, is to dig a shaft on the ground first and dig at the bottom of the well with a shield machine. The shield machine is a movable steel tube structure, and the excavation part of the head is a circular turntable covered with blades. When it comes to desperation, close to 1/4 soil. Under such pressure, the subway tunnel becomes solid. In the process of propulsion, most of the soil is cut off by the cutter head of the shield machine and then enters the soil bin through the opening of the cutter head. The soil is stirred into tassels in the warehouse and transported to the soil wall of the truck by screw and belt conveyor, and the books are transported to the ground. About 65,438+00% of earthmoving will remain, and the tunnel and pavement will be backfilled after the tunnel is completed.

Where did the rest of the dirt go? Why haven't you seen many transport vehicles running at ordinary times? The reason why we can't see the earth-moving truck is because the transportation time is almost at night, the vehicle bumps on the road, and it is inevitable that the muck will fall. Night transportation can be cleaned before dawn, so as not to interfere with daytime traffic and affect nearby residents. Moreover, there is a waste soil treatment center in the suburbs, which is specially used for storage and professional treatment, and the treated soil is sent to various green belts.

You know, the growth of plants in the green belt needs suitable soil, and the excavated soil can come in handy. In addition, some expenses are used for the construction of roads and river banks, as well as land for buildings and parks. Usually need a lot of soil, just can be sold as building materials.