Why build a tunnel?

Since ancient times, building roads and bridges has always been regarded as a benefit to the people. In modern society, roads and bridges are also considered as the basis of economic development, and they are as important as blood vessels in human body. However, when people build roads or railways, they will inevitably encounter obstacles from mountains and rivers. In the case that it is difficult to implement the traditional "opening the road on the mountain and bridging the bridge when encountering water", building a tunnel may be the most practical and effective method. The railway or highway tunnel that passes through the mountains is much simpler than the Panshan railway or highway. When the sea blocks the way and it is not convenient to bridge, the cross-harbour tunnel is like the magic of the Monkey King, which enables us to reach the other side smoothly.

In addition, tunnels have many functions, such as underground drainage or water supply tunnels in cities, tunnels for laying gas pipelines or large transmission lines, subway tunnels, water diversion tunnels for agricultural irrigation, and special tunnels for national defense and military affairs. It was once a fantasy to open the cross-harbour tunnel, but today it has become a reality, serving mankind day and night. For example, the cross-harbour tunnel across the English Channel is 50 kilometers long, of which 37 kilometers pass through chalk rocks at a depth of 40 meters below the seabed. The diameter of the tunnel is 7. 3 meters, and two railways.

The Channel Cross-Harbour Tunnel started in July 1987 and was completed in June 1993. This is one of the largest civil projects in Europe. The opening of this tunnel shortened the train time from Paris to London to three hours, which played an important role in the economic development of Europe, especially Britain and France. The longest subsea tunnel built in the world is the Japanese Han Qing subsea tunnel. It spans the Tsutsugaru Strait in Japan and connects the main island of Japan and Hokkaido. Its total length is 53. 85 kilometers, the deepest point is 240 meters from the sea, and the inner diameter of the tunnel is 9. 6 meters, can drive high-speed trains and ordinary trains. The whole project cost US$ 4.5 billion, and more than 65.438+million people participated in the construction. At the same time, the project also won the 19 patent technology award and set a number of world engineering records.