With so much water in the sea, how was the submarine tunnel built? After reading it, I admire Chinese engineers

In order to relieve the traffic pressure on the ground, the underground transportation network is also increasingly developed, and the subway and the submarine tunnel are the main forms of underground transportation. We are no strangers to tunnels. When building a road on the ground, if a large mountain is encountered, in order to improve efficiency and convenience, a tunnel is often dug from the bottom of the mountain to go directly through it.

But can you imagine digging a tunnel under the sea? The sea is full of water, how are underwater tunnels dug?

At present, there are still quite a lot of construction methods for submarine tunnels. There are conventional tunnel excavation methods such as the stubborn machine method and the drill-and-blast method. However, these two methods are only suitable for excavating the seabed with a large number of rock layers. Most of the construction of submarine tunnels adopts the immersed tube method and the shield method.

The immersed pipe method is to sink the pre-cast pipes to the seabed and then connect them to each other. The most important thing for the immersed tube method is to do a good job of waterproofing. Before the pipeline sinks, both ends should be plugged to ensure 100% water tightness. After sinking into the seabed, it will be assembled into a tunnel through precise butt joints.

The subsea tunnel of the Hong Kong-Zhuhai-Macao Bridge in China uses the immersed tube method.

It was constructed by connecting 33 pipes on the seabed. In order to prevent the urban management tunnel from being washed by the waves for a long time in the deep sea, the urban management tunnel must be deeply buried in the seabed silt. And the use of gravel backfill technology to cover the pipeline.

Although the immersed tube method is particularly advantageous in terms of water tightness, it can achieve 100% watertightness. However, this method is only suitable for short-length subsea tunnels, and it is difficult to carry out immersion operations on the seabed with turbulent currents.

Of course, there is also a shield method, which can just make up for the shortcomings of the immersed tube method. It uses a large shield machine with extremely high sealing performance. Push directly into the silt on the seabed, laying pipelines in the process, and assembling concrete segments while excavating.

The surrounding rock is supported by the shield shell and segments to prevent collapse inside the tunnel, which can be regarded as a fully mechanized construction method. Therefore, the shield method is the most widely used. Of course, the construction of submarine tunnels is often based on the actual conditions of different sea areas, and a variety of methods are used to excavate in order to achieve the best results.