Chapter 130

"I remember that this question was left to Professor He and Gu Lu to complete separately yesterday. Zheng Chun said, glancing at Gu Lu with deep meaning, and then his gaze fell on Professor He in the front row.

"Professor He, have you got an answer to this question about the impact of tidal action on waterproof performance?" asked Zheng Chun in a calm tone.

Professor He, who was named, lowered his head in shame, "I...... No. ”

Yesterday he had a busy day, until two or three o'clock in the morning.

But it will take him at least half a day to come to a conclusion.

This answer had long been expected by Zheng Chun, so he did not mean to blame Professor He.

Then, Zheng Chun refocused his gaze on Gu Lu, who had a pair of panda eyes, and asked with a smile, "What about you, Gu Lu?"

At the same time, dozens of pairs of eyes fell on Gu Lu in unison.

Being stared at by so many people, Gu Lu didn't look uncomfortable.

He looked calm, nodded slowly, and said with a smile, "I think I can tell you my conclusions." ”

Receiving a completely different answer from what he expected, a hint of surprise flashed in Zheng Chun's dark eyes.

Zheng Chun leaned forward, his eyes as sharp as an eagle staring at Gu Lu.

"Gu Lu, are you sure you made it?"

Gu Lu shrugged his shoulders and smiled bitterly, "Zheng Gong, I don't think you think I deceived everyone on such a big occasion." ”

"Then please begin your story. Zheng Chun stretched out his hand and motioned to Gu Lu.

Then, leaning back in his chair, he exhaled softly.

Others may think that it is not a big deal that Gu Lu can solve that problem in one day, because there are fourteen academicians standing behind him.

But Zheng Chun knew very well that Gu Lu had not consulted any academicians about that question.

In other words, Gu Lu completely relied on his own strength to solve the problem that even Professor He couldn't solve in one day!

In other words, in the field of engineering, Gu Lu's ability is no less than that of an average level of professor.

But Gu Lu is a mathematician!

…………

In the auditorium, countless pairs of eyes were locked on an inconspicuous corner in the back row, the young over-the-top figure.

The average age of the more than 100 experts attending the pre-construction seminar on the Bohai Tunnel was about 40 years old.

And Gu Lu, who is just in his early twenties, is particularly eye-catching among them.

Gu Lu connected the computer to the large screen in the center of the hall.

Then open a file in paper format.

The title is "Research on the Influence of Tidal Action on the Waterproof Performance of Segment Joints of Large-section Submarine Shield Tunnels".

Gu Lu cleared his throat, and under the gaze of a pair of scrutinizing and probing eyes, he began to tell the question in a tone that was not in a hurry.

"For submarine shield tunnels, the focus of waterproofing is on waterproofing joints, which is the weakest point in the entire waterproofing system. The waterproofing of the joints is mainly achieved by the elastic gasket, and the current mainstream shield tunnel gasket is the EPDM gasket. For EPDM gaskets, the amount of opening directly determines the ability of gaskets to resist water pressure when the gasket material, cross-section and gasket groove cross-section are constant. ”

“…… My method is to establish the longitudinal equivalent stiffness model of the shield tunnel, use the finite element method to calculate the internal force of the shield segment under tidal load, and then calculate the opening of the annular joint at different positions of the tunnel, and analyze the influence of tidal load on the waterproof performance of the segment of the large cross-section submarine tunnel. ”

"The first step is to establish a longitudinal equivalent stiffness model for shield tunnels......"

Due to the existence of a large number of circumferential and longitudinal joints between the segmental structures of shield tunnels, the cooperative load deformation mechanism between segments and between segment rings is very complex.

So the construction of this model is very complicated.

In order to more easily analyze the mechanical deformation performance of the segment ring at the longitudinal joint, Gu Lu adopts a mathematical model called "longitudinal beam-spring model".

"In the second step, a stratigraphy-structural model was established, the shield tunnel was simulated using beam188 beam elements, the cross-section type was defined as a circular pipe cross-section, the inner diameter was 13.5 m, the outer diameter was 14.5 m, and the model cross-section was calculated ......"

Gu Lu's narration continued.

In the front row, more than a dozen academicians were whispering while listening to Gu Lu's narration.

"Gu Lu's idea is very ingenious!" an academician sighed.

"That's right. Academician Guo stroked his beard and commented, "He completely converted this engineering problem into the language of mathematics, and then used mathematical modeling methods to solve it." ”

"To be honest, I really can't see through this kid Gu Lu now. He has a strong talent in the field of engineering, but after all, the contact time is short and the foundation is not solid. I thought that this question would stump him, but it seems that his ability is still at ease?" Academician Li shook his head and smiled bitterly.

"But this kid has suffered a lot! You don't see his dark eyes, they are almost like pandas. I don't know what time it was last night. ”

"Young people, you still need moderation, it's always too empty and it's not good. ”

"Give him a few strings of kidneys at noon today and let him make up for it. ”

"Correct solution!"

Gu Lu, who was entering the state of speech, did not realize that several academicians and bigwigs were concerned about their health problems.

He was already fully in the state, and under the surprised eyes next to him, he talked eloquently.

“…… Once the model is constructed, the next step is to calculate the parameters, first of all, the first parameter, tidal load!"

“…… The second parameter is the longitudinal equivalent anti-bending system reduction coefficient of the tunnel, according to the specific size of the shield tunnel structure, 9 ring segments are established along the longitudinal direction. The segmental structure is simulated using the solid element SOLID95. ”

"When 56 M36 bolts are arranged between the rings, the flexural stiffness of the elastic and plastic two stages of the ring is Kθ1 = 5.45 × 10^11 N· m/rad， Kθ2 =5.32 ×10^10 N·m/rad。 The equivalent flexural stiffness reduction factor is: ηM=(EL)eq/EI=Kθ/El/l. ”

Gu Lu's speed of speech was neither fast nor slow, so most of the people present were able to keep up with Gu Lu's train of thought.

But the more they listened, the more surprised they became.

Because Gu Lu's solution idea was very different from what they expected.

An engineering problem, in the hands of Gu Lu, was forced to become a mathematical application problem by constructing a mathematical model and formulating parameters!

This is the existence that surprised many of them, and even surprised them.

However, there are no loopholes in Gu Lu's narration, which is enough to prove that Gu Lu's thinking is correct.

Gu Lu's narration gradually came to an end.

"The rotation angle θ of the annular indirect seam surface under the action of bending moment can be calculated by the formula θ=cosφ (π/2 φ)·sinφ/sin^3φ, and the maximum annular seam opening caused by tidal load is 0.271 mm. ”

Gu Lu concluded: "This value means that the impact of tidal action on the waterproof performance of the joint is low, but the rubber gasket is required to meet the water pressure resistance of at least 0.5 MPa when the dislocation amount is 10 mm and the opening amount is 15 mm in the limit state!"

That's all for me. Gu Lu closed the file, raised his head, and looked at everyone with calm eyes.

Bang Bang Bang ~~

Zheng Chun looked at Gu Lu with appreciative eyes, and was the first to take the lead in applauding.

Then there was a flurry of applause in the auditorium.

Gu Lu solved such a problem at such an age, and he really deserves such applause.

Among those who looked at Gu Lu, there were not a few questioning eyes.

After all, Gu Lu's performance today really didn't look like what he should be at his age.

But what is more in sight is a kind of praise and appreciation for the younger generations.

"Gu Lu, can I ask a question?" In the front row, an old expert looked at Gu Lu with curious eyes.

You say. ”

"That question is obviously an engineering problem, but why would you want to solve it in the language of mathematics?"

"The reason is actually quite simple. ”

"Huh?"

"Because...... I'm a mathematician!"

…………

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