How was the undersea tunnel built? Why can it be watertight? China's infrastructure is too strong

Before the submarine tunnel technology could not be conquered, two land separated by the ocean or two independent islands could only rely on ships for transportation. When there was bad weather, the ships could not pass, and the traffic was very inconvenient. Therefore, some people think that since there are tunnels through mountains on land, why not build a tunnel that can cross the ocean? If this tunnel can really be built, it will bring a lot of convenience to the traffic on both sides of the strait, but due to technical limitations, the idea of ​​this undersea tunnel can only be temporarily stranded.

Now this idea has been successfully realized. More than 20 undersea tunnels have been established around the world. The establishment of undersea tunnels not only connects inconvenient places, but also makes the traffic no longer affected by the weather, and the impact on the ecological environment has also reached minimum. For example, in the Hong Kong-Zhuhai-Macao Bridge built by China, the underwater tunnel is 40 meters deep, but it has never leaked once in 120 years. Then there are also many people who are very curious about the construction process of the undersea tunnel. How was the undersea tunnel built in a place full of water? Since the undersea tunnel is in sea water, will there be a risk of leakage?

First of all, how is the submarine tunnel built? There are a total of 4 methods for digging a submarine tunnel, namely the drill and blast method, the immersed tube method, the roadheader method and the shield method.

The first drill and blast method, the drill and blast method, is also known as the mine method. This is a method of excavating the section by drilling and blasting and then constructing the tunnel. Before using this method, the section must be excavated and the outline must be designed before construction. The drill-and-blast method has various characteristics such as strong adaptability, so it is used in the construction of the Xiamen Xiang'an Subsea Tunnel and the Qingdao Jiaozhou Bay Tunnel in China. Xiamen Xiang'an Tunnel is the first undersea tunnel in China, and it is also the tunnel with the largest cross-section drill and blast method in the world. Up to now, Xiamen Xiang'an Tunnel has been in use for eight years, and all functions are still normal, and there is no water leakage. In good condition, you can continue to use it.

The second method is the roadheader method. The roadheader method uses a large machine to crush the rock, and at the same time uses the supporting equipment to transport the crushed rock away to form a tunnel. The roadheader is more suitable for the excavation environment with hard stones. For example, the British and French tunnels connecting the United Kingdom and France are built by the roadhead method.

The third method is the shield method. The shield method is also one of the most commonly used methods for excavating submarine tunnels. The shield method is to propel the shield machine under the ground, and use the casing and segments to support the tunnel. The equipment sends the soil out of the hole, and then splices out concrete segments to form the tunnel body. Different from the roadheader method, the shield method is more suitable for use in the case of soft soil. The Tokyo Bay Tunnel in Japan is constructed by the shield method.

The fourth method is the immersed tube method. The immersed tube method is to build a section of tunnel on the land in advance, and then seal the two ends with a partition wall to prevent seawater from entering, and dig a flat ditch on the seabed after the preparation is completed. Since the pre-sealed pipe is filled with air, the pipe can float on the water with great buoyancy. Use the boat to drag the tunnel pipe to the planned position, then fill the pipe with water to increase the weight, and then the pipe will Submerge to the position where the trenches were dug in advance, gradually connect the various pipes, and waterproof the joints. At the same time, fill in the previous trenches, pump out the water, and remove the partition walls. Done.

The submarine tunnels built by this method have the characteristics of high seismic safety, fast construction speed, and less disturbance to the environment. The Pearl River Tunnel in Guangdong and the Hung Hom Submarine Tunnel in Hong Kong are both constructed by this method.

The Hong Kong-Zhuhai-Macao Bridge is the first offshore immersed tunnel built in China. It is also the longest undersea tunnel in the world. The total length of the undersea tunnel is 5,664 meters. After years of use, it is watertight. Why is it so amazing?

First of all, because the soil of the Hong Kong-Zhuhai-Macao Bridge is relatively soft, if this problem is not solved, it will easily cause water leakage. Therefore, after many experiments, the engineers laid 2-3 meters of stones underneath to form a composite foundation. To meet the needs of various aspects of strength and durability, it took a few years to prepare concrete that meets the above conditions, which very meets the needs of immersed tube engineering. At the same time, in order to ensure the quality of the project, the project also has a special document, which strictly manages the implementation of each project, and has a set of very complete and strict standards for quality.

At the same time, because most of the tunnels are buried in the silt, special personnel are also equipped to conduct regular maintenance and inspection of the tunnels, and in order to ensure various safety issues, there is a safety gate in the tunnel every 135 meters to avoid accidents. unexpected situation. Although the construction methods of these undersea tunnels sound very simple, it is very difficult to know that the undersea tunnels are built in the deep sea, and the undersea tunnels built in China have not leaked for a long time. It does not make people feel the superb construction technology of China.