The rise of nanometers

November 26th.

Qiongzhou Strait in the southwest corner of Xuwen County.

On the seabed about 17 kilometers away from Lighthouse Point, at the construction site of the first phase of the Qiongzhou Strait Undersea Tunnel, all construction workers entered safety special vehicles.

Huang Xinming, chief engineer of Feipeng Engineering, and Li Feng, deputy chief engineer of China State Construction Engineering Corporation, stared at the simulation screen on the operation page.

Since the undersea tunnel is excavated from both ends to the middle, the 37-kilometer-long Qiongzhou Line 1, which is under the sea, is 33.6 kilometers long, and the meeting point of the two ends is at 16.8 kilometers.

After more than a year of full-scale construction, taking into account the geological conditions where the sediment layer is prone to collapse, after breaking through the land rock layer area, the construction team adopted a pipe jacking construction method combined with a shield machine.

On average, we can advance 50 to 60 meters every day, and today is the day when the two ends finally meet.

The construction of the section of tunnel from Lingao County has been completely stopped, waiting for the last 10 meters of sediment layer in Xuwen County to be excavated.

"5 meters, temporary pipe jacking to keep up." Li Feng shouted nervously.

"receive."

The temporary pipe jacking made of super materials slowly moves forward with the shield machine under the action of eight sets of hydraulic presses.

Behind the jacking pipe is a huge alloy barrier net to prevent sudden collapse in the front and seawater carrying a large amount of soil from hitting the construction area.

Behind the sediment barrier, hundreds of workers are busy. They are all equipped with special exoskeletons, which are specially customized diving exoskeletons.

Even if the front suddenly collapses, they can survive in the sea water. There was a collapse in the Lingao section last month, and a large amount of sea water rushed into the construction area. The workers successfully evacuated with the help of exoskeletons and special safety vehicles.

The construction of the Qiongzhou Strait Undersea Tunnel has accumulated a lot of experience and technology for domestic tunnel construction under complex geological conditions. These experiences and technologies can be used in the future construction of undersea tunnels in other regions.

Time passed by minute by minute.

The shield machine and pipe jacking are advancing slowly, and the workers are quickly laying the pipe wall.

4 meters...

3 meters……

…

The moment when the last few dozen centimeters of the temporary cement layer were chipped away and pushed down by the shield machine.

The surveillance camera arranged on the Lingao section clearly recorded this scene and was synchronously transmitted to the safety car.

"Successful!" Huang Xinming, who had been silent all this time, raised his arms and shouted.

"Very good!"

"We did it!"

"Ha ha……"

Many people cried with joy, or were so excited that they could not speak incoherently.

As the last 10 meters of soil were penetrated, a group of engineers and workers woke up from their excitement and began to do the final finishing work.

The pipe jacking continued to move slowly southward with the TBM, and the workers spent more than three hours connecting the final pipes.

Stepping out of the safety car, Li Feng looked at this huge tunnel. It is the largest and most difficult submarine tunnel in the history of mankind to build a series of submarine tunnels.

Standing at the bottom of the tunnel, Li Feng seemed to have entered the kingdom of giants.

"Very shocking!" Huang Xinming on the side was also amazed.

Due to the casing solution, they have only completed the outer pipe so far, and there is an inner pipe behind it. The inner pipe does not need to consider tunnel excavation or rock and soil collapse. The construction speed is very fast. Currently, 31 kilometers of length have been built. The last 6 kilometers remain.

Li Feng put on his helmet to relieve the chest tightness: "The outer tube is completed, and the inner tube will be closed in about two months."

"We have to prepare for the next step." Huang Xinming said while returning to the safety car.

Just because the outer pipe is closed successfully and the inner pipe is closing soon does not mean the work is completed. They also need to consider the construction of the ventilation well.

The ventilation issue of the ultra-long undersea tunnel is actually very important. Unless the highway passing function is not set up and only railways are allowed to pass through, the ventilation issue does not need to be considered.

The interior of the undersea tunnel is very airtight, and the average depth of the Qiongzhou Strait undersea tunnel is 150 to 180 meters below sea level, and the length reaches 37 kilometers.

Once a large number of motor vehicles enter it, the engine needs to burn and do work, which will cause a large amount of oxygen inside the tunnel to be consumed and exhaust gas to increase rapidly.

If you only rely on natural ventilation, it will not be able to meet the consumption inside the tunnel, and hypoxia will soon occur.

Due to the lack of oxygen inside the tunnel, although electric vehicles can be used normally, fuel-based engines will shut down, and the driver and passengers on the vehicle may suffocate to death.

It’s not possible for every car that enters a tunnel to be equipped with an oxygen bottle!

That picture is too beautiful to imagine.

To maintain normal gas composition inside the tunnel, building ventilation shafts has become an essential task.

The safety car drove north, and Huang Xinming and Li Feng came to the ventilation shaft No. 001. The design of the ventilation shaft was not to be placed directly on the outer pipe, but to open a horizontal longitudinal pipe first.

The diameter of the horizontal longitudinal pipe is 12 meters and the length is 500 meters. It is also designed as an inner and outer pipe. There are three gates inside to separate the ventilation shaft and the tunnel in an emergency.

Inside the horizontal longitudinal pipe, there are air intake pipes and exhaust pipes, which are forced to ventilate through the electric motor. The diameter of the air intake pipe and exhaust pipe is 1.5 meters. Two air intake pipes and exhaust pipes are arranged in a ventilation well.

The air intake pipe and exhaust pipe extend from one end of the horizontal longitudinal pipe to the ventilation platform on the sea surface. In order to maintain the balance of the ventilation well, a balance fixed column with a depth of 200 meters is set below the horizontal longitudinal pipe.

Huang Xinming entered the construction site of ventilation shaft No. 001. Currently, the ventilation shaft is almost completed. As long as the ventilation platform from China Shipbuilding Industry Corporation is delivered, it can be connected.

The Qiongzhou Strait Undersea Tunnel requires a total of 8 ventilation shafts, 6 of which are on the sea and 2 on land.

Originally, four ventilation wells were enough, but for safety reasons, we designed twice as many as just in case.

Although the probability of a major earthquake is relatively small, it is not impossible, and Qiongzhou is an area prone to typhoons. In the event of an accident on the ventilation platform, backup ventilation shafts can be used to ensure normal ventilation inside the tunnel.

Huang Xinming checked it and found no problems. He turned to Li Feng and said, "The problem here is not big. Let's go to the inner pipe construction area to have a look."

"Okay." Li Feng nodded and recorded the situation of the ventilation shaft on his tablet.

The safety car continued to go north, and there were inner tubes along the way. Hundreds of workers, wearing work-type exoskeletons, were busy silently.

The inner tube is actually a super highway.

However, since it is under the sea, there are more things to consider.

For example, lighting systems, emergency systems, rescue systems, and fire extinguishing systems must be considered.

During the design process, many engineers and designers still felt that the inner and outer casings were not enough, so they also added a watertight cabin design plan.

If in case one of the pipes, both the inner and outer pipes, breaks, a watertight hatch can be used to separate the broken area from the normal area.

In addition, emergency escape passages are designed using the horizontal longitudinal pipes of the ventilation shaft. In an emergency, these four ventilation pipes can be turned into escape passages for personnel to leave, and can also be turned into entry passages for rescuers.

Designers and engineers have considered possible unexpected situations to ensure that the Qiongzhou Strait Undersea Tunnel can be used safely for more than a hundred years.

Thank you for your support (ω｀)