As one of the daily means of transportation, the subway is becoming more and more popular, so do you know how the subway tunnel is dug out? Now digging the subway tunnel is not like before shovelled manpower digging, of which the shield machine is indispensable, it is an important mechanical equipment in the construction of the subway project, generally used to dig the interval between two stations.

Shield tunneling machine, full name of shield tunneling machine, is a special tunnelling engineering machinery, modern shield tunneling machine has the excavation cutting soil, rock, conveying soil ballast, gravel, assembly tunnel lining, measurement guidance correction and other functions, in the shield tunneling machine through the formation of a spacious underground cement tunnel.

The body of the shield machine is made of thick steel plates welded together to withstand the pressure of the surrounding soil layer, creating a working face for digging the tunnel. Its nose is cut out with a large, slow-rotating disc containing a number of fast-rotating tools, shaped less like a drill and more like the cutterhead of a Philip razor. At the tail of the shield machine, tunnel lining segments (a kind of prefabricated parts to construct tunnel walls) are assembled into a tunnel, and concrete is poured into the gap between the lining and the well wall to strengthen the tunnel and prevent the infiltration of groundwater. When the shield tunneling machine is driven forward to a certain distance, its forward pushing force can be borne by the friction between the tunnel lining and the formation. In the concrete tunnel formed by the shield tunneling machine, two rails are laid, one is used to transport excavated slag and gravel, and the other is transported into the lining segments and concrete.

When the front of the shield machine encounters loose soil or groundwater, the shield machine will use refrigeration technology to make the loose soil or groundwater in front of the cutter head ice, so as to break the ice forward. Therefore, the shield machine is also suitable for digging cross-river or undersea tunnels.

The process of digging a subway tunnel is: first dig a large deep hole at the platform, install a shield machine in the deep hole, and then start to drill the ground. In order to speed up the process of subway civil construction, two shield machines can be used between two platforms to move towards each other and carry out excavation. The shield machine can increase the underground digging efficiency of the subway by 8 to 10 times, and in the construction process, there is no need for large-scale demolition on the ground, no blocking traffic, no noise in the construction, the ground does not settle, and does not affect the normal life of residents. Editor/Xu Shengpeng