I! Pretending to Be Reborn, Director of Doomsday Hoax

After a while, Xu Qiu said: "Follow what I said and improve the shield machine."

"For the shield tail seal, use three rows of steel wire water-stop seal brushes, and fill the inside with sealant."

"Joint seals are lip-shaped rubber seals."

"And, on the outside of the main bearings, triple lip rubber seals filled with grease and HBW seal grease!"

The more Ni Jianbai listened, the more clear his mind became.

Xu Qiu used rubber seals, sealing grease and other materials on such a large scale to improve the waterproof and sealing performance of the shield machine?

Can relying on this alone prevent water pressure breakdown?

However, Xu Qiu just paused for a while, then continued to speak.

"Another point is to adopt a controllable two-stage screw conveyor slag removal system with anti-surge function!"

Xu Qiu looked at Ni Jianbai and said, "Professor Ni, what is the configuration of our shield machine?"

In the underground city of Tiandu No. [-], Ni Jianbai is responsible for the excavation of [-] tunnels with shield machines.

Therefore, he knew these things very well, and blurted out: "Considering the limitation of the slag discharge capacity of the screw machine, the size of the opening size of the cutterhead, and the characteristics of adapting to the abrasiveness of sand and pebbles, we have improved the wear resistance of the cutterhead. ."

He continued: “Additionally, to break the harder sand pebbles, break the pebble glue structure, and protect the soft soil cutters, we have hobs.”

"In order to increase the rigidity and wear resistance of the cutter, and at the same time prevent hard pebbles from damaging the cutter, we have prepared large blades and scrapers for the shield machine."

"The type and opening ratio of the cutter head are all carefully measured and finally screened out to prevent the occurrence of collapse accidents."

The stratum that Tiandu Dungeon passes through has poor stability, high air permeability, rich groundwater, high water level, and high water pressure.

The optional ground reinforcement measures in the sand and pebble formation are not effective. When changing the tool, if the tool is changed under pressure and the ground grouting is used to strengthen the bottom layer, the risk of tool change will increase.

However, conventional jet grouting piles or hole-digging piles are used to reinforce the tunnel surface, which is inconvenient in terms of time and environment.

Speaking of this, Ni Jianbai was very embarrassed.

Unless a new tunneling technology is designed, how can these problems be solved?

After a brief silence, Xu Qiu spoke again and said, "From now on, follow the method I said to improve the configuration and related parameters."

Ni Jianbai and the others looked at each other, not understanding what Xu Qiu was going to do.

"The cutter head is replaced with a panel-shaped structure, and the "zero three three" grinding-resistant steel plate welded with HARDS400 is selected."

"The excavation diameter is 6.28 units, the opening ratio is 20.00%220, and the particle size of sand and pebbles that can pass through the cutter head opening is controlled at [-] mm."

"In terms of knife configuration, it has increased to 32 single-edged hobs, four double-edged center knives, 28 front blades, and eight edge scrapers."

"Finally... on the top of the blade of the screw conveyor, a HARDS400 wear-resistant steel plate with a thickness of [-] mm is welded!"

Ni Jianbai, Zou Baitao and others were stunned.

Ni Jianbai was in a daze. He always felt that if he modified the shield machine according to Xu Qiu's method, he would create a machine completely different from the huge shield machine of Longguo today...

His eyes were filled with shock and uncertainty, and he asked: "Director Xu, you...are you going to transform a brand new shield machine?"

Xu Qiu nodded slowly, with deep eyes, and said, "I call it Earth Pressure Balance Shield Tunneling Machine."

Earth pressure.....Balanced TBM?

At this moment, Zou Baitao, Ni Jianbai and others were completely silent and full of doubts.

Xu Qiu didn't hold back, and explained:

"The so-called earth pressure balance shield is to fill the soil bin between the excavation surface and the partition with the excavated soil and sand, inject improved materials into it as needed, and use appropriate earth pressure to ensure the stability of the excavation surface. "Through the screw conveyor installed through the partition, the soil can be discharged while advancing."

"The earth pressure balance shield tunneling machine is the shield machine that perfectly adapts to this tunneling method."

"During construction, soil and sand are filled between the excavated two-layer partition, and it is pressurized to meet the stability requirements of the excavated surface."

"At the same time, in order to obtain the amount of soil displacement suitable for the thrust of the shield, it is necessary for the inspectors to measure the earth pressure and the unearthed disk, and to control the number of revolutions of the screw excavator and the advancement speed of the shield to achieve a balanced state! "

Ni Jianbai's hands were trembling slightly, "A... a shield machine that specializes in conquering water-rich sand and pebble formations?"

According to what Xu Qiu said, he kept rehearsing in his mind, and soon his train of thought got stuck.

Ni Jianbai asked in astonishment:

"According to your design, the earth pressure balance shield is different from ordinary shield machines in that in order to ensure the stability of the excavation surface, the pressure of the pressure chamber needs to be properly maintained."

"Once the pressure in the soil bin is insufficient, the risk of water gushing or collapse at the excavation surface will increase."

"And if the pressure is too high, it will cause an increase in the torque or thrust of the cutter head, which will cause problems such as a decrease in propulsion speed or ground uplift."

"Director Xu, how to manage the pressure on the soil warehouse?"

In Xu Qiu's mind, the structure of the earth pressure balance shield tunneling machine and the details of the tunneling technology emerged.

After a while, he gave the answer, saying: "There is a basic idea for soil warehouse management."

"The pressure is the highest, and the static earth pressure needs to be used for the purpose of controlling the settlement of the ground surface. The minimum pressure must also be able to allow a small amount of surface settlement, but the active earth pressure can be used for the purpose of ensuring the stability of the excavation surface!"

Ni Jianbai nodded and said, "Director Xu, this is the way to balance the pressure of the soil warehouse in a static state!"

"Once the excavation starts, then our shield machine can no longer use static earth pressure and active earth pressure! It can only passively accept the force of water-rich sandstone formation!"

Xu Qiu looked at Ni Jianbai appreciatively.

He has mastered the knowledge of mechanics at the master level, and on this basis, he has comprehended the earth pressure balance shield technology rewarded by the system.

Xu Qiu understands how ingenious this design is, it is not a mechanical solution that humans can think of at all!

Otherwise, the world's engineering community would not have been plagued by water-rich sandstone formations for nearly 100 years, and could not give a solution.

however,

After Xu Qiu gave the general parameters of the earth pressure balance shield machine and explained the working principle and characteristics,

Ni Jianbai actually completed the rehearsal of this new type of shield machine and shield tunneling technology in the first place, and has already discovered some of the most difficult points to solve!

"Professor Ni, you are right. This can only solve the pressure balance of the soil silo when the machine is at rest."

When Xu Qiu said these words, everyone was suddenly discouraged.

Could it be that Director Xu has no solution?

Ni Jianbai looked at Xu Qiu eagerly,

He has already noticed that there is a smile on the corner of Xu Qiu's mouth. This smile proves that Xu Qiu has already made up his mind!

really,

As soon as Xu Qiu's voice changed, his face instantly became serious, and he said:

"During the excavation process, three points must be achieved to ensure the balance of the pressure in the soil bunker."

"The first is to use the screw soil remover to control the number of revolutions, so as to control the speed of the soil entering the shield machine."

"Second, control the propulsion speed of the shield jack!"

"If the internal pressure is small, the speed will be reduced, and if the internal pressure is large, the propulsion speed will be increased."

"Third, ensure that the soil bin is full when excavating the muck!"

"Control the amount of muck to a certain amount. In this case, the pressure of the soil chamber formed by the muck is easier to balance with the water and soil pressure outside the excavation surface of the cutterhead!" Ni Jianbai's eyes lit up.

Actively control the excavation speed, rotation speed, etc. to regulate the pressure of the soil bin.

This method is indeed very clever!

"but."

Ni Jianbai discovered the problem again, "However, Director Xu, the third point you mentioned, to achieve this condition, you must ensure the balance between the amount of soil excavated and the amount of soil excavated!" "However, in the strata of Tiandu Dungeon In the excavation process, due to the weight of the surrounding rock will fluctuate to a certain extent during the excavation,

And affected by factors such as the type of additive, the amount added or the way of soil discharge, the weight of the discharged muck will also change.

Therefore, it is very difficult to properly grasp the amount of soil displacement!

In addition, as a dumping soil, its state can be changed from a semi-solid state to a fluid state, and its properties are various...

It is very difficult to control the collapse of the excavation surface, the settlement of the foundation and the balance of the pressure of the soil bin only based on the management of the amount of soil discharged! "

Xu Qiu looked at Ni Jianbai and answered, "Pressure management and excavation volume management are never isolated."

"The pressure management of the pressure chamber and the management of the excavated soil volume must be carried out simultaneously!"

"Pressure chamber management has already been said."

"Then the key point is the management of the amount of excavated soil!"

"At present, I can think of two kinds."

"Volume Management and Weight Management."

"Volume management method, using the method of calculating the number of muck trucks or calculating from the number of revolutions of the screw earthmover."

"The weight management method is to use the weight of the muck truck for acceptance!"

"Although it will not be too precise, the shield machine also has its own pressure regulation system inside, and it is enough to control the pressure within a certain range of pressure difference!"

Xu Qiu looked at the construction site in the distance.

A thousand tunnels are now being excavated simultaneously.

For the dungeon scene, three tubes were used to assemble.

The workers are very skilled. Starting from the lower standard A segment, the standard segment is installed alternately on the left and right sides, and then the next adjacent B segment is spliced, and finally the wedge-shaped K segment is installed.

In Xu Qiu's mind, the precise structure of the earth pressure balance shield machine emerged.

He slowly taught everyone the subtlety and greatness of this new shield machine!

Ni Jianbai and others were fascinated, like students, eagerly absorbing this knowledge...

They knew for the first time that the earth pressure balance established by the shield machine had nothing to do with the buried depth of the shield machine!

Xu Qiu's explanation followed, "According to the principles of rock and soil mechanics, Coulomb's earth pressure theory and Rankine's earth pressure theory are not suitable for calculating the earth pressure of shield machines..."

"The earth pressure balance setting of the shield machine is related to the parameters of the shield machine. When the roadheader is trying to excavate, it is necessary to establish the earth pressure parameters of the formation according to the geological conditions. The earth pressure parameters are mainly based on the screw machine in addition to the formation reasons. The excavation efficiency has a great relationship with the ratio of slag soil improvement, dispersant and foam bentonite."

Everyone felt that their understanding of the shield machine had been refreshed.

Their previous calculation of the pressure of the shield machine was based on rock mechanics and pressure theory.

So...they've been on the wrong track all along?

"Why... why?" Ni Jianbai couldn't accept it for a while.