Looking at the screen, the thick sediment on the surface of the tunnel bed, everyone was silent.

If it looks so thick to the naked eye, then when measured, I'm afraid it's six or seven centimeters deep, right?

The immersed tube in front was installed so smoothly that even the fourteenth section of the immersed tube, which had been installed the day before yesterday, did not have any problems, so that everyone could not believe the reality in front of them.

The sun was shining on this day, and it was a rare good weather.

There are no torrential rains, no ocean currents, why is there such a thick accumulation of sediment in this foundation trough?

"What about yesterday's test results?" Chief Engineer Su lowered his eyes and dragged over the thick stack of materials at hand.

Chief Engineer Lin has a good memory, and raised his hand to pull out a document: "This, yesterday's situation was very good, and there was feedback this morning, there was sediment in the foundation groove, but it was not much at that time, and it was not so thick within the controllable range." ”

Everyone knew that the matter was serious, and no one was idle, all desperately calculating.

Divers quickly delivered the latest data, which they carefully analyzed and verified before submitting the latest report.

"The sediment thickness reached 6 to 8 centimeters in less than 24 hours, which is just over the standard!"

"According to the latest measurements, the thickest accumulation of sediment reached 8.6 centimeters. ”

"If by the previous standards...... The standard bulk density of sediment siltation on the foundation bed surface of immersed tube installation is 1.26 kg cubic centimeter, and the siltation thickness of the returned silt shall not be greater than 4 cm......"

But that was the previous standard, which was developed in accordance with international standards.

In fact, with the addition of Lu Zi'an, their standards have long been raised to a jaw-dropping height.

Lu Zi'an always has a way to make the accuracy reach the most perfect state.

But at the moment, let alone according to Lu Zi'an's standards, even according to international standards, this section of the immersed tube is not in place.

Chief Engineer Lin pinched the sweat in his palm, but in just a few minutes, his back was soaked with cold sweat: "This ......"

He exchanged glances with Chief Engineer Su and saw the heaviness in each other's eyes.

And the inquiry at the construction site also pierced everyone's hearts like a needle: "Then this immersed tube, is it still installed?"

On the screen, seawater gently caresses against the immersed tube.

The huge immersed tube hangs above the foundation trough and has been parked for a long time.

The entire command room was in a state of agitation.

If the installation is withdrawn, it will mean that the construction of the world-famous undersea tunnel will have to be delayed......

But if it continues, even if Lu Zi'an is here, it will be impossible to erase the existence of these sediments.

Chief Engineer Su is still thinking about a solution, and Chief Engineer Lin has made a decisive decision: "Notify everyone and hold a meeting." ”

The construction team was on standby, and the headquarters had quickly assembled in the conference room.

After many days of running-in, these people led by Lu Zi'an are now named the technical support team.

The same team as them, there are two more teams with them.

Chief Engineer Su and Chief Engineer Lin sat down at the chief with serious expressions: "Okay, everyone can speak freely, and you can say anything you have directly." ”

The headquarters and the teams are basically divided into three parties.

One side, represented by Lu Zi'an, insists on quality first: "If the quality can't keep up, what's the point of building this bridge?"

On the one hand, the construction period is the first: "The construction period is so rushed, and the time that was finally squeezed out should be postponed because of the mere sediment?"

The remaining ones abstained.

They want quality, but they are reluctant to build the project, so they are in a dilemma and simply abstain.

Is it quality or duration?

Heated discussions ensued.

"The standards of consultants are too high, in my opinion, many bridges and tunnels are implemented according to international standards, and there have been no problems!"

"If you can do your best, why compromise?"

"If you can do your best, who doesn't want to do it? The problem is that you can't do it now! Who knows whether this sediment will be silted in the long term or in the short term, so if you don't install it this time, what will happen if there will be more sediment piles next time? Every day it drags on, it's a huge amount of money being exported!"

"If it is installed like this, there will be more sediment in the later stage, which will have a bad impact on the entire tunnel, have you thought about the maintenance cost in the later stage?"

Both sides have their own opinions, and no one can convince anyone.

When they quarreled to a certain extent, Chief Engineer Su asked in a deep voice, "Consultant Lu, what do you think?"

Lu Zi'an, who was named, raised his eyes and glanced at him, and lightly touched his fingertips on the table: "I think it's best to make the situation controllable, and then dock, don't try to be quick for a while, leaving a bunch of worries." ”

That's really true.

Chief Engineer Lin pressed his eyebrows and looked at the time, from the time the problem was discovered to now, they had been discussing for four hours.

"Alright. His voice was low and hoarse.

When he raised his eyes, everyone looked at him, as if he had aged ten years in an instant.

"Stop sinking. Chief Engineer Lin's eyes were sad, and he made this decision that made him very painful, but had to make: "Pass the order to go down and withdraw the immersed tube to the dock!"

"Chief Engineer ......" Someone looked at Chief Engineer Su and Lu Zi'an in disbelief.

Is there really no other way?

Chief Engineer Su waved his hand and interrupted their inquiry: "Go ahead." ”

The news spread to Beiqi and the whole country paid attention.

Under the coordination and guidance of the Ministry of Transport, CCCC Fourth Harbor Engineering Survey and Design Institute, Tianjin Water Transport Engineering Research Institute of the Ministry of Transport, Nanjing Hydraulic Research Institute, and Estuarine and Coastal Research Institute of Sun Yat-sen University all dispatched senior experts for emergency support at the first time......

25 top experts in China who have studied sediment, tides and meteorology in the Pearl River Estuary all year round have established a "national team" for technical research.

The expert group has held 36 special meetings, carried out more than 300 risk investigations in 9 categories, and set up 6 sets of fixed monitoring base stations and 24 sets of monitoring instruments in the 120 square kilometers of sea around the construction site.

It has completed 200 groups of geological sampling surveys and more than 30 density tests to analyze and study the causes of sediment.

Formulate response measures and explore the possibility of establishing early warning and prediction mechanisms.

Everyone was nervous and worried.

Lu Zi'an was also in a hurry, but he was really powerless.

Marine sediment dredging is a worldwide engineering problem, and engineers have considered the sediment dredging on the seabed of the Pearl River Estuary as early as the design stage and formulated a construction solution.

Previously, they had been following this plan and completed the installation of the first 14 immersed tubes without danger.

However, as the tunnel was extended, the hydrological conditions of the seabed gradually changed.

The foundation trough east of the immersed tube "E15" is located at the southern tail of the Tonggu Shoal, which is directly affected by the fresh water of the estuary and the sediment discharge from the shoal, and the siltation at the tail of the Tonggu Shoal moves southward, and the construction of the immersed tube is in a hydrodynamic sediment environment that is conducive to sediment siltation.

Especially in winter and spring, due to the action of tidal current, eastward wind and waves, the sediment of Tonggu shoal starts to spread again, which directly affects the area of the foundation trough east of the "E15" immersed tube, so the siltation of the foundation trough becomes more and more serious.

Based on a large number of on-site measured data, and combined with dynamic geomorphology, satellite remote sensing inversion, mathematical model experiments and other related research, the experts have conducted countless heated discussions and meticulous research.

During this period, the only thing Lu Zi'an could provide was to make a detailed model deduction of the content they proposed.

Amazingly, as one possible factor after another was ruled out, they finally found some problems in this model.

In the nearby sea, there are many sand mining ships.

These surrounding sand mining activities seem to be common, but in fact, they have a great impact on the siltation of the immersed pipe foundation groove of the Hong Kong-Zhuhai-Macao Bridge Island Tunnel Project.

The main source of sediment for the abnormal siltation of the foundation trough is caused by the sand mining operation near Neilingding Island, and the high sand content muddy water formed by sand mining enters the foundation trough by direct transport and re-handling.

When the situation was discovered, the project department immediately made a detailed report to the superior.

According to the results of a large number of detailed and rigorous research by the research team, the official announced the latest statement the next day: from now on, sand mining will be stopped at 7 sand mining sites within more than 10 kilometers upstream of the immersed tube operation area.

During the Spring Festival this year, everyone stayed in Zhuhai.

There was no hard and fast rule, but no one left.

Everyone is making detailed preparations for the re-docking of the E15 immersed tube after the holiday.

After all sand mining activities stopped, the sea water gradually became clearer, and the amount of quicksand silt on the seabed slowly entered a controllable range......

On the morning of the sixth day of the Lunar New Year, the divers sent back the latest data, confirming that the sediment in the foundation tank had been cleared, and the floating crane dragged the E15 and slowly sailed out of the dock again.

The wind on the sea was biting, but everyone's hearts were warm.

The most troublesome problem has been properly solved, and now the image of the seabed is much clearer, so this time it will be fine!

Halfway through the immersed tube, the construction team had already seen the boats of the construction team from afar, and before everyone could breathe a sigh of relief, the construction team urgently sent back the latest news: "Oh no, a large amount of silt suddenly appeared on the seabed, according to our estimates, the total amount of cover is about 2,000 cubic meters!"

Chief Engineer Lin propped his palms on the table and said in a condensed voice: "Repeat, how much?"

"Not less than two thousand cubic meters!"

Someone in the command room couldn't help but shout: "Why didn't you find out before! Why did you say it now!"

The ship has sailed out, the immersed tube has been undocked!

This is a waste of millions of dollars!

"Report! I really didn't have it before, it just happened all of a sudden!"

Originally, all of them were anxiously waiting for the arrival of the immersed tube, but the staff who had been staring at the sea found that the originally clear water suddenly became extremely turbid, and then they realized that something was wrong and quickly reported it.

At the same time, everything on the bottom of the sea began to be clearly displayed on all screens.

Looking at the overwhelming mud, Chief Engineer Su sat back in his seat.

The situation is worse than they imagined.

After data analysis, someone said in a deep voice: "Chief engineer, according to our calculation results, this should be an avalanche-like collapse of the newly returned silt on the slope of the foundation trough!"

There was silence in Headquarters.

How much I was looking forward to it before, how desperate I am now.

Lu Zi'an lowered his eyes and did not speak.

To say not to be sad, that is false.

I have made so many models, and even many people have thought of solutions to various unexpected phenomena, but in the face of reality, they have no power to fight back.

Two thousand cubic meters.

Chief Engineer Su and Chief Engineer Lin looked discouraged, but they still remained calm and gave the most urgent order: "E15 return to the dock." ”

"Chief Engineer ......"

Thinking of the hard work of these days, thinking of the sleepless nights, some people can't help but burst into tears.

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