The distance between the two places is the shortest in a straight line , but sometimes, in many areas , the communication between the two places is blocked by rivers or the ocean . To develop the economy , communication must be indispensable , so people invented water transportation .

But for some areas that are very close to each other, what else can be used to strengthen communication? Yes, build bridges .

The longest sea-crossing bridge in the world - Hong Kong-Zhuhai-Macao Bridge

The history of Chinese bridges can be traced back to the era of clan communes 60 million years ago . Although the development of modern bridges is only more than 100 years old, China is a country called "infrastructure crazy" , so our technology for building modern bridges has reached It has reached the world 's leading level , such as the construction of the Hong Kong-Zhuhai-Macao Bridge .

What are the benefits of cross-sea bridges ? What issues need to be considered when building a sea-crossing bridge ? What kind of difficulties will the construction of cross-sea bridges face ? Why did you choose to build a subsea tunnel instead of a bridge across the sea?

Next, let's find out why Dalian and Yantai , facing each other across the sea , did not choose to build a sea-crossing bridge ? Let's increase knowledge together!

How was the undersea tunnel built?

Dalian and Yantai facing each other across the sea

How can I go from Dalian to Yantai ? There are three ways, by car, by boat and by plane .

From the map, Dalian and Yantai are both located at the chin of the "rooster" , but they are far away from each other because of the Bohai Sea . In terms of straight-line distance, it must be 150 kilometers .

There are many ships in the Bohai Sea area

If you choose to take a boat , it will take about 6.5 hours , and if you take a plane , it will only take about 1 hour .

It seems that it is quite convenient to choose between Dalian and Yantai, and it will not take a lot of time .

But now many people choose to drive by themselves when traveling , so there are more ways to go.

From the navigation point of view, it takes at least 1,384 kilometers to travel, and it takes nearly 15 hours to arrive after passing through 10 expressways such as Qinbin Expressway and Jingha Expressway .

More and more people have the need to buy a car and are more inclined to travel by car

However, the toll cost is more than 600 yuan , and the fuel cost is not included. If there are any holidays such as "May Day" and "11th" Golden Week , it is not impossible to block the expressway for a day or two.

The whole journey is connected by a big C , so some people have to ask, why not directly connect Yantai and Dalian from the Bohai Sea? Wouldn’t it be more convenient to communicate between two or more places by directly erecting a sea-crossing bridge , like the Hong Kong-Zhuhai-Macao Bridge, Zhoushan Sea-crossing Bridge and Donghai Bridge ?

The Zhoushan Cross-sea Bridge is 27 kilometers long

The benefits of cross-sea bridges

If the sea-crossing bridges between Yantai and Dalian are built, then for the two provinces of Shandong and Liaoning , the exchanges will be more in-depth.

And the traffic will be more convenient . If it is a 55-kilometer Hong Kong-Zhuhai-Macao Bridge, the whole journey will only take half an hour to 40 minutes . If it is a 150-kilometer sea-crossing bridge between Dalian and Yantai, the whole journey will only take About an hour and a half .

The beautiful scenery of Yantai

In terms of transportation costs and time-consuming, the cross-sea bridge can crush ships and planes , and as an important foreign economic and trade seaport in Northeast China, Dalian is also developing continuously in terms of tourism.

If the two places are connected, it will not only promote the economic development of the two places , but also drive the economic development of the surrounding cities .

At that time, as a former industrial city , it will also have more opportunities to revitalize the industrial industry in Northeast China , drive the development of transportation in Liaoning and Shandong , and further develop it into a modern metropolis .

Bohai Rim Port Group—An Important Support for Regional Economic Construction

Difficulties in building cross-sea bridges

But building a sea-crossing bridge is not an easy task, and according to the environment of the Bohai Sea , the country prefers to build an undersea tunnel between the two places rather than a sea-crossing bridge .

It is understood that the submarine tunnel project connecting Dalian and Yantai has been planned and designed in 2010 , and in 2015, the construction plan of the Yantai submarine tunnel has been officially released . It is planned to invest 260 billion yuan , but there is no movement in this project.

Concept map of the undersea tunnel

Let’s put the matter of the undersea tunnel first, and now let’s understand why we don’t build a bridge across the sea . In fact, we can see from the plan of this undersea tunnel that the country wants to develop the two places jointly .

But building a bridge over 100 kilometers across the sea is not an easy task.

The second longest bay bridge in China - Jiaozhou Bay Bridge

• Too expensive and time consuming

How much did the construction of the Hong Kong-Zhuhai-Macao Bridge cost? More than 120 billion , how long does it take? In 9 years , the Hong Kong-Zhuhai-Macao Bridge is currently the longest sea-crossing bridge in China, with a length of 55 kilometers .

However, it may take 150 kilometers to build the sea-crossing bridge between Dalian and Yantai . Whether it is time-consuming or expensive , it is almost three times that of the Hong Kong-Zhuhai-Macao Bridge , which is a huge investment of more than 300 billion yuan and more than 20 years .

Three ways to build bridges across the sea

If the cost of building the bridge is recovered through tolls, we can roughly calculate how long it will take.

Before 2020 , according to the relevant forecast of the cross-sea passage of the Bohai Strait, the potential passenger flow between the straits can reach about 300 million person -times. 240 million passengers.

The maximum daily traffic flow on the Zhoushan Sea-crossing Bridge is more than 60,000 vehicles

According to the current toll charging standards of some sea-crossing bridges, we propose that the toll of this sea-crossing bridge is 80 yuan . Calculated by a single person, the annual toll can reach 19.2 billion yuan at most , so at least 16 It takes about a year to recover the cost .

But obviously, this is already the maximum limit of our calculation, and the actual cost recovery is still unknown. This is only a matter of capital and time , and the bigger problem is the difficulty of construction .

The Zhoushan Sea-crossing Bridge under construction was the largest island-land connection project in the world.

• Marine geology and weather have a big impact

The sea areas of Dalian and Yantai are just in the seismic zone . There are mainly three seismic zones in the Bohai Rim region , namely the North China Plain Zone, the Zhangjiakou-Bohai Sea Zone and the Tanlu Fault Seismic Zone . These three seismic zones are all staggered. Earthquakes frequently occur in the Bohai Rim region .

For example, Tangshan, where the Great Tangshan Earthquake occurred that year , is located in the North China Plain . Therefore, the construction of cross-sea bridges here may face the situation that the bridge will break due to the impact of the earthquake .

Schematic diagram of seismic zones near the Bohai Sea

Secondly , the water area for the construction of the cross- sea bridge should not be too deep, otherwise it will increase the difficulty of underwater piling. The average water depth of the Hong Kong-Zhuhai-Macao Bridge is 30 meters , but the difficulty it faces is indeed world-class , and the maximum water depth in the Bohai Sea area reaches 85 meters . , obviously there will be more difficulties in underwater piling.

In addition, although the Bohai Sea is an inland sea , the climate change in the water area will also have a great impact on the construction.

The Bohai Sea belongs to the temperate monsoon climate , with northwesterly wind blowing in winter and southeasterly wind blowing in summer. The average wind speed in winter can be 6-7 m/s . In January, the frequency of strong winds above level 6 will exceed 20% .

How sea water affects climate

In addition, there is still a severe ice age in the Bohai Sea in winter . The outer edge of the floating ice in Liaodong Bay can reach 46 nautical miles , accounting for 30% of the sea area. The thickness of some sea ice can even exceed 25 cm .

So if you want to build a sea-crossing bridge, there is definitely no way to build it on the sea in winter .

In winter, the Bohai Sea and the Yellow Sea enter a severe ice age

• Affect the navigation of ships

Generally, sea-crossing bridges mainly appear in waters without a main channel , because a sea-crossing bridge needs to make piers underwater . That is to say, on the inner side of the sea-crossing bridge, it is best not to have a large port , and the bridge cannot cross the channel .

Drive the pillars into the seabed section by section with an offshore pile driver

The Bohai Sea is an inland sea that is close to closed. The most important transportation in the Bohai Sea is water transportation. The port group around the Bohai Sea is one of the five major port groups in China and plays an important role in the economic development of the northern coastal and inland areas of China.

There are many 100 million-ton ports along the route , such as Dalian Port, Qinhuangdao Port, Qingdao Port, Rizhao Port, and Tianjin Port , which directly account for half of China's 100 million-ton large ports .

If a sea-crossing bridge is built, it is estimated that one of the masts on those ships will break every ten minutes , and it will also affect the route and speed of the ship's navigation. In this way, not only will it not promote economic development, but it will also affect freight efficiency .

The port group has gradually become the logistics base in the global international trade and transportation system

Therefore, to build a cross-sea bridge in the Bohai Sea, no matter the cost, time or difficulty of the project , it will not be lower than the Hong Kong-Zhuhai-Macao Bridge.

In contrast, the construction cost of the submarine tunnel will be lower than that of the cross-sea bridge, the construction difficulty will be lower, and the time will be shorter, and the submarine tunnel will not affect the navigation of ships in the ports around the Bohai Sea , and the car will not drive on the seabed. It will be affected by weather such as strong wind and fog on the sea surface .

A sea-crossing bridge produces short-term vortex vibration due to strong winds

Therefore, when considering connecting Dalian and Yantai, the country will give priority to undersea tunnels instead of sea-crossing bridges.

Although the Yanda Undersea Tunnel has not yet officially started construction , there is very little information received . Perhaps this huge project is still under intensive research .

The first cross-harbour traffic tunnel in Hong Kong - Hung Hom Cross-Harbour Tunnel

After all, the Seikan Tunnel, the longest in the world, is only 54 kilometers long , and the seabed part is only 23 kilometers long , but our Yanda submarine tunnel is more than 100 kilometers long .