I! Pretending to Be Reborn, Director of Doomsday Hoax

He felt that the education he had received for so many years and his research on shield machines were gradually being subverted.

Just because of Xu Qiu's words...

Xu Qiu gave the answer to this question and said: "The earth pressure sensors of the shield machine are mainly distributed in the soil chamber, and they reflect the pressure in this area in the earth chamber. The pressure of the earth chamber is only the shield machine's advancing The parameters in the process can be large or small, and are related to the geotechnical characteristics of the formation where the shield machine is located."

"Is that clear enough? To put it more simply, if the ground is quite hard, then no matter what the depth is, the pressure felt by the sensor in the soil bin will be very large!"

"On the contrary, even at 1000 meters underground, if the soil here is abnormally soft, the pressure will not be too high!"

Xu Qiu paused, and continued: "One more thing, the excavation condition of the shield machine is the factor that least disturbs the rock and soil."

"It only causes local shear failure and punching shear failure to rock and soil, rather than overall shear failure."

"Therefore, the earth pressure of the shield machine is related to the self-stabilization performance of the soil at this time, and cannot be simply calculated by Coulomb earth pressure and Rankine earth pressure."

Xu Qiu found a piece of paper and simply drew a schematic diagram of the structure of the earth pressure balance shield machine.

In an earth pressure balance shield machine,

There are generally six earth pressure sensors in the earth bin.

The position of the sensor is different, and its pressure changes with the height, the upper part is smaller and the lower part is larger, and the pressure near the inlet of the screw machine is the highest.

Xu Qiu clicked on the design drawing and said: "Since the slag outlet of the screw machine is at normal pressure, there is a pressure difference between the inlet and outlet of the screw machine. When the screw machine rotates, the slag in the soil bin will be discharged along the screw machine. to the slag outlet belt

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"Moreover, the soil bin of the shield machine should keep half or one-third of the soil during excavation, and it should be continuously mixed with dispersant, water, and gas to increase its flow plasticity so that it can be discharged from the screw machine mouth."

"When the shield machine is advancing, the knife first touches the tunnel surface, and the balance of the tunnel surface is broken by mechanical force, so as to achieve the purpose of cutting the soil."

Ni Jianbai swallowed his saliva, his pupils shrank, his eyes were horrified, and he asked: "Director Xu, here, you marked the pressure gas and shield body, what is the purpose?" Xu Qiu glanced at it and said: "The pressure gas and shield body body, which can play a role in maintaining pressure and supporting the soil."

"What about earth pressure? How do you calculate earth pressure?!"

Ni Jianbai's eyes were dull, and he suddenly felt that he didn't understand the shield machine.

In front of Xu Qiu's knowledge, for the first time, he felt crushed, it was completely incomparable greatness and talent!

The supervisor of the construction technology department also looked dull and shocked at this moment.

Neither the earth pressure nor the world's engineering community can give an authoritative calculation scheme.

Basically, it can only be roughly estimated based on the sensors on the surface of the shield machine.

no way,

The shield machine is indeed an important engineering tool, but the theoretical knowledge involved in it is too much.

Even Ni Jianbai dare not say that he fully understands shield machines.

Moreover, human beings' scientific and technological capabilities still have too many limitations when facing nature.

Even now, there is no authoritative way to measure earth pressure.

Xu Qiu searched in his mind.

I was pleasantly surprised to find that the earth pressure balance shield machine is also equipped with earth pressure measurement method!

Xu Qiu laughed.

At this moment, Ni Jianbai suddenly burst into joy.

Could it be... Director Xu has a solution? !

Xu Qiu said quietly: "Earth pressure is not impossible to calculate."

"The key is the calculation formula of Terzaghi's earth pressure."

"The soil bin is behind the cutter head and in front of the front shield. In addition to the stirring rod, the center rotation device, and various pipelines, the maximum seal of the rotation center is 1mMpa, and the general setting pressure is 0.3Mppao." "According to Taisha The calculation formula of foundation soil pressure can estimate the average pressure at the center of the excavation bin with appropriate corrections."

Ni Jianbai was short of breath, of course he also knew that it could be estimated after correction, but how to correct it?

This is the difficulty that plagues the engineering world! !

Xu Qiu's eyes were deep and his voice was steady, and he said: "The friction between the foundation and the foundation is very large, this is because the surface of the foundation is completely rough."

"When the foundation fails, the foundation soil wedge interface under the foundation bottom is in an elastic equilibrium state, which is called the elastic core. The angle between the two boundary surfaces and the foundation bottom is equal to the internal friction angle of the foundation soil.

"When the foundation fails, it will slide along the curve along one of the boundary corners. The passive stress state area can be obtained..."

"On the basis of the above assumptions, the Terzaghi ultimate bearing capacity formula can be obtained from the static equilibrium condition of the rigid core, and this is the current earth pressure!"

At this moment, the construction site was extremely silent.

Only the sound of the shield machine digging the tunnel in the distance and the workers yelling at work is left.

gollum..

After a long time, Ni Jianbai blushed, looked at Xu Qiu excitedly, and said, "Director Xu, if...you can really design such a shield machine according to your statement!"

"Then, our excavation speed will be further improved!!"

At this moment, the eyes of this group of engineers are filled with irrepressible excitement!

The earth pressure balance shield machine means that Longguo once again breaks through the world's engineering problems......

This is an epoch-making shield machine, which will completely mark the shield machine technology of Longguo, leading... no, it is to dominate the world! !

"According to the tunneling speed of this shield machine, the speed of our Tiandu Dungeon can be increased."

"More importantly, for some areas with more complex strata, such as the wilderness and mountains in the north, and the plateau in the northwest... With the help of the earth pressure balance shield machine, we will be able to open a thousand tunnels faster, Consolidate the dungeon structure and start building!!"

Zou Botao's body was also shaking.

He thought that Xu Qiu was just providing an idea to get the water-rich sandstone formation faster.

However.…

This young bureau chief directly took out a shield machine technology that dominates the world! !

From today onwards, the shield machine technology of Longguo will completely surpass industrial powers such as Berry Country, Cherry Blossom Country, and Orthopedic Country. Weak times

II

. .

"Director Xu, the treasure of the Dragon Kingdom!" Zou Baitao looked at Xu Qiu excitedly and muttered to himself.

Boom boom boom.

After Xu Qiu left, Tiandu Dungeon began a thorough construction!

Previously, upon hearing the news that Xu Qiu was coming to inspect,

Ni Jianbai and the others specially asked the construction site to take it easy, so as not to cause too much dust and affect Xu Qiu's body.

At this moment, Xu Qiu had already left.

And, leaving an earth pressure balance shield technology!

Ni Jianbai kept recalling Xu Qiu's teachings in his mind.

On this day, this group of engineers seemed to have been enlightened, and they were completely transparent.

The shield machine... can it be designed like this?

They thought that knives and blades were the most important thing. However, Xu Qiu's appearance told them that these things were just auxiliary devices.

Using the pressure of the soil silo to excavate layer by layer, this method... is unique! !

"Director Xu must not be disappointed." After a long time, Ni Jianbai opened his eyes.

He put on his hard hat and said: "Let's go, back to the construction site, Director Xu has already taught us the earth pressure balance shield technology, as a student, we have to bring this idea of ​​Director Xu to reality Come!!"

He kept deducing it in his mind.

The three most critical issues are retightening the connecting bolts, keeping the true circle, and segment assembly.

Retightening the connecting bolts is a good solution.

After the first ring segment is assembled, the axial connecting bolts can be fully tightened by using all the shield jacks to apply pressure evenly.

However, the problem is,

After the shield continues to excavate, under the thrust of the shield jack, the soil or water pressure behind the shield tail will deform the lining,

At this time, the connecting bolts that were tightened during assembly will loosen.

In the process of consulting with Xu Qiu, Ni Jianbai has already thought of a solution.

That is, after advancing to a position where the thrust of the jack cannot be affected, use a torque wrench, etc., to tighten the connecting bolts again, and then re-tighten.

Of course, the position of retightening will change with the outer diameter of the tunnel, tunnel alignment, segment type, geological conditions, etc., and needs to be changed according to the soil quality.

In earth pressure balance shield technology, true circle maintenance is also very important.

Because the segments are assembled into a true circle and remain in a true circle state,

This is very important to ensure the dimensional accuracy of the tunnel, improve the construction speed and water-tightness, and reduce the settlement of the ground.

It is not difficult to achieve this. After the segment ring is released from the shield tail, the grouting slurry is hardened and the segment gap is filled with density. At this time, a true circle holding device is used to restrain the segment deformation.

The most difficult point is the assembly of the segments.

Due to the use of earth pressure balance technology, the segment structure of this shield machine is different from other shield machines.

Its most critical parts are several soil bins.

The quality of splicing will directly affect the quality of the soil bin, which will eventually affect the excavation efficiency of the earth pressure balance shield machine and the mechanical wear rate.

The splicing process is very cumbersome, which can only be carried out in detail.

For example, before the segments are assembled, the previous lining surface should be cleaned.

Control the thrust and stroke of the shield propulsion jack, and keep the posture of the shield and the stability of the excavation surface;

According to the segment position and assembly sequence, the rings are assembled piece by piece...

Ni Jian[Bai said: "There is another key point. The tightening torque of the segment connecting bolts should meet the design requirements. After the segments are assembled and come out of the shield tail, the segment bolts should be retightened in time."

"It's not only about the quality of the splicing, but also the retightening of the connecting bolts."

Ni Jianbai heaved a long sigh.

He tapped his hard hat and stepped into the management department of the shield machine where the workers come and go...

In the near future, the world's first epoch-making shield machine that can pass through water-rich sandstone strata will be born here.