How to build an undersea tunnel? What difficulties need to be overcome?

We know that human beings have been trying or looking for ways to change nature since the dawn of time, and now, as human science has been constantly evolving, bringing progress and bringing about some ways to change nature, such as skyscrapers.

Rockets, cell phones, satellites, and so on are all things that humans have created by altering nature. These are all things that human beings have made with their wisdom and hands-on ability. And one of the things that also shocked us, is the undersea tunnel.

If you want to build an undersea tunnel, you need to start from the following points, and the difficulties to overcome are also as follows. <>

1. The following methods should be used to build an undersea tunnel. First of all, if we want to build an undersea tunnel, we must plan and design, after all, the undersea tunnel must refer to the seawater conditions in the area, as well as its geological landform and other shapes to ** whether such an undersea tunnel can be built in the area. Because in the undersea tunnel, it has to withstand a huge pressure, because the sea water has not fallen, 10 meters and 20 meters, its pressure is different, which urgently needs to test the designer's skills.

When the design drawings are planned, it is the actual construction, and the construction process must be completed by large machines, and it must also be isolated from the seawater, which is its difficulty. <>

Second, technological breakthroughs need to be overcome. Secondly, we also learned that if we really want to build an undersea tunnel, we have to overcome technological breakthroughs. Because the undersea tunnel has been popularized in many regions in China, this is also a task that has only been completed in recent years.

In the past, if we wanted to complete such an undersea tunnel, we would definitely have to declare or learn from other countries. <>

Third, huge financial and human resources are needed. The last point is that if you really want to build an undersea tunnel, you will definitely need a huge amount of capital and human resources. Because every meter of the nautical tunnel needs to be piled up with money, and the construction of the undersea tunnel is completely smashed with money.

The construction of submarine tunnels is a costly and difficult thing, in the construction process, we need to overcome the seabed is not a way, directly from the foundation to build, and another is that the water leakage requirements of our building materials are quite high.

There are still many problems to be solved in the construction of the submarine long shield tunnel, such as the waterproof performance of the waterproof gasket under the high water pressure of the seabed and the durability of the 100-year service life; Film-forming effect of slurry in seawater environment; long-distance slurry transport; Wear and replacement of shield long-distance tunneling tools; The possible impact of the submarine fault zone on the shield tunnel, etc., a series of problems are waiting to be tackled by scientific researchers!

First, all materials need to be waterproof, and the treatment between faults must be even more delicate; Second, the danger of workers' work is higher, and drowning accidents will inevitably occur when working in water.

There are two ways to construct undersea tunnels:

The first is excavated in rock formations on the seabed, such as the long tunnels in the English Channel, which are opened by advanced shield machines. The second is to use prefabricated large steel pipes or concrete square boxes, sink them to the pre-treated foundation of the seabed, and seal the joints with concrete on the outside to drain the internal seawater. Then make a reinforcing lining on the inside, and it becomes a tunnel.

This is the case with the Straits Tunnel in Hong Kong. An undersea tunnel is a tunnel dug into the rock formation under the seabed. The train enters the undersea tunnel from the ground through the approach road and then up to the surface from the opposite coastal approach road.

The middle horizontal part is not the undersea tunnel, the slopes on both sides are the coastal approach roads, and the upper horizontal part is the exposed part of the ground. Sometimes, the undersea tunnel is not necessarily completely horizontal depending on the topography, geology and other specific conditions. The cross section of the tunnel is circular or horseshoe-shaped when excavated, and the bottom of the tunnel can also be laid with oil pipelines and cables, etc., and some double-track tunnels are dug into two single-line submarine tunnels.

Nowadays, technology is constantly advancing, and transportation has become more and more convenient and fast. Now people want to go**, even if it takes two or three days to get there, they can play and enjoy the scenery in their favorite places. But do you know why tunnels are being built under the sea?

What is the reason for this? Let me answer your doubts.

The land or islands across the sea can only be navigated by ship. In the event of rough sea conditions and weather, it becomes extremely dangerous to rely on ships to cross the strait. As a result, people suddenly wondered if it was possible to build underground tunnels under the sea to provide a faster and safer way for people on both sides of the strait to pass.

However, at the time, the construction of the undersea tunnel was extremely difficult and costly, so the idea was just a dream.

Today, this seemingly impossible task has become a reality! More than 20 undersea tunnels have been built around the world, which connect the mainland with the mainland, the land with the island, and the island with the island, bringing great convenience to transportation and people's life and travel. Especially for some straits with strong winds and waves, and long distances, because it is inconvenient to erect cross-sea bridges, the construction of undersea tunnels has become the best choice.

It does not occupy an area, does not hinder the navigation of ships, and is not affected by strong winds, fog, and has little impact on the ecological environment, which is really a very safe all-weather traffic method.

The most famous undersea tunnel in the world is the English Channel Tunnel, located on the seabed between Cheriton in the UK and Freyton in France, with a total length of one kilometer, which is an electric traction double-track railway tunnel and is also known as one of the world's seven engineering wonders. In order to facilitate the communication between Britain and the European continent, Britain and France finally broke ground to dig the Channel Tunnel after more than 200 years of brewing. After 7 years of arduous construction, it was completed and opened to traffic on May 6, 1994.

The Channel Tunnel connects the British Isles in the Atlantic Ocean to the European mainland, and has become a very important link in Europe's transportation network. It consists of two main tunnels and one service tunnel. The main tunnel has a diameter of meters and is used by high-speed trains between London and Paris, and by trains that specialize in carrying a variety of vehicles.

The service tunnel is built in two main tunnels with a diameter of one metre for ventilation and maintenance services, with a transverse tunnel at intervals to the main tunnel. In the past, it took 5 hours to travel from Paris to London by boat through the Channel, but now it takes only 35 minutes to take a high-speed train through the tunnel, which greatly reduces the travel time. At present, the tunnel can carry 45 million passengers and 26 million tons of freight a year.

1. Shield method.

The shield method is a fully mechanized construction method in the construction of the underground excavation method, which is to advance the shield machinery in the ground, and prevent the collapse of the tunnel through the shield shell and segment support the surrounding rocks.

At the same time, the soil body excavation is carried out with a cutting device in front of the excavation, and the hole is transported out of the hole by the excavation machinery, and the jack is pressurized and jacked in the rear part, and the precast concrete segment is assembled, and a mechanized construction method of tunnel structure is formed. The Tokyo Bay Undersea Tunnel in Japan was constructed using the shield method.

2. Drill and blast CRD excavation.

The drilling and blasting method is mainly a construction method for excavating sections and building tunnels and underground works by drilling hole blasting method. When the drill and blast method is used, the entire section is excavated to the design contour, and the lining is built accordingly. The undersea tunnels that have been built and are under construction in mainland China, Xiamen Xiang'an undersea tunnel, Qingdao Jiaozhou Bay undersea tunnel, and Xiamen Haicang undersea tunnel are all constructed by mining method.

3. Immersed tube method.

The immersed tube method is a construction method for building tunnels underwater. The immersed tunnel is an underwater tunnel built by floating several prefabricated sections to the sea surface (river surface) site separately and sinking them one by one and installing them in the dredging foundation groove. A number of cross-harbour tunnels in Hong Kong are constructed using the immersed tube method.

4. Roadheader method.

The TBM method is a method of excavating tunnels, roadways, and other underground spaces. Referred to as TBM method, it uses special large-scale cutting equipment to shear, extrude and crush the rock, and then transport the crushed stone out through supporting transportation equipment. The Channel Tunnel, which connects the UK and France, was excavated using the TBM method.

Famous tunnels

1. Bering Strait Undersea Tunnel.

The Bering Strait Undersea Tunnel is a 105-kilometer-long undersea tunnel that runs through the bottom of the Bering Strait, which can be called the "world's longest undersea tunnel". The tunnel connects Siberia, Russia, and Alaska, USA. The undersea tunnel will include a high-speed rail and a highway, multiple oil pipelines, cables and fibre optic cables.

2. Shenzhong Bridge Undersea Tunnel.

In accordance with the "East Tunnel and West Bridge" scheme, the Shenzhen-Zhongshan Bridge has a total length of kilometers of cross-sea bridges and tunnels, adopts a combination of bridges and tunnels, and has two navigable holes, and adopts a submarine immersed tunnel at the branch channel and the alum waterway of Shenzhen Airport, with a total length of kilometers.

The project officially started on December 30, 2016, and the construction of the west artificial island began, and it is expected to be completed and opened to traffic in 2024. It is expected that the land formation of the western artificial island will be completed first; The start of the East Artificial Island Project was started; Finally, the main tunnel project was fully started.

The undersea tunnel is constructed in the following way:

1. The construction method of tunnels and underground engineering is mainly used to excavate the section by drilling and blasting method, and the entire section is excavated to the design contour when the drilling and blasting method is used, and the lining is then built. The undersea tunnels that have been completed in mainland China include the Xiamen Xiang'an Tunnel and the Qingdao Jiaozhou Bay Undersea Tunnel, both of which are constructed using the mining method.

2. The immersed tube method is a construction method for underwater construction tunnels, and the immersed tunnel is to float a number of prefabricated sections to the sea surface (river surface) site, and sink them one after another and install them in the dredging foundation groove, so as to build underwater tunnels, and many submarine tunnels in Hong Kong are constructed by immersed tube method.

Introduction to the Cross Harbour Tunnel.

An undersea tunnel is a tunnel built on the seabed to connect the two sides of the Taiwan Strait, and is for vehicular traffic. The undersea tunnel can be divided into three parts: the submarine section, the coastal section and the approach road, of which the submarine section is the main part, which is buried under the seabed, connected with the coast at both ends, and then connected with the ground line through the approach road.

Generally speaking, the construction of undersea tunnels requires the installation of shafts on both sides of the river, and the installation of ventilation, drainage, power supply and other equipment. There are more than 20 undersea tunnels that have been completed or planned to be constructed in the world, mainly in Japan, the United States, Western Europe, Hong Kong, Kowloon and other regions. The undersea tunnel does not occupy an area, does not hinder navigation, and does not affect the ecological environment, and is a very safe all-weather strait passage.

The construction method of the undersea tunnel is as follows:

1. Drilling and blasting method.

The drill and blast method, also known as the mining method, is a method of excavating a section and then building a tunnel by using drill hole blasting. Before using this method, the section must be excavated and the profile must be designed before construction. The drilling and blasting method has various characteristics such as strong adaptability, so it is used in the construction of Xiamen Xiang'an Submarine Tunnel and Qingdao Jiaozhou Bay Tunnel in China.

2. Roadheader method.

The TBM method uses a large machine to crush the cover, while the crushed stone is removed and the tunnel is formed using supporting equipment. TBMs are more suitable for excavation environments with hard stones, such as the Anglo-French tunnel connecting England and France, which was built using the TBM method.

3. Shield method.

The shield method is also the most commonly used method for excavating undersea tunnels today, in which the shield machine is propelled under the ground while the shell and segments are used to support the tunnel. In front, the cutting device is used to excavate the soil, and the soil is sent out of the hole with supporting equipment, and then the concrete segment is put together to form the tunnel pipe body. Unlike the TBM method, the shield method is more suitable for use in soft soil, and the Tokyo Bay Tunnel in Japan was built using the shield method.

4. Immersed tube method.

The immersed tube method is to build a tunnel on land in advance, then seal the ends with a partition wall to prevent seawater from entering, and dig a flat ditch on the seabed after preparation. The tunnel pipe is dragged to the planned location by boat, and then the pipe is filled with water to add weight, and then the pipe sinks to the pre-dug trench, gradually connecting the individual pipes. The undersea tunnel established by this method has the characteristics of high seismic safety, fast construction speed and low interference to the environment.

The Anglo-French Channel Tunnel

The Channel Tunnel, also known as the Channel Tunnel, the Eurotunnel and the Channel Tunnel, is a railway tunnel connecting the British Isles of the United Kingdom to Europe and France, which opened on 6 May 1994. It consists of three parallel tunnels with a length of 51 km, with a total length of 153 km, of which the length of the tunnel in the submarine section is 3 38 km, which is currently the longest submarine tunnel in the world.

The diameter of the lining of the two railway tunnels is, the diameter of the excavation tunnel is, and the diameter of the lining of the middle logistics service hole is, and the diameter of the excavation tunnel is. From the signing of the Treaty of Canterbury on February 12, 1986 between France and Britain on the tunnel connection to the official opening of the tunnel on May 7, 1994, it lasted more than eight years, and it is also the world's largest construction project with private capital.

The above content reference: Encyclopedia - Cross Harbour Tunnel.