Shield machine.

This is still a novel concept for the new Kyushu.

Even in Zhang Zhi's time, ordinary people had never heard of this kind of machine at all.

It's not as simple as a superficial principle. It's not what everyone thinks, a drill bit in front of you can push forward.

Shield, in fact, means that the two are one.

A complete TBM should be a TBM in front to push forward, and a TBM in the rear to lay the tunnel while excavating. Prevent the excavated tunnel from collapsing, or the upper soil and rock layers from falling due to vibration and filling the tunnel.

The principle of the TBM is not difficult, but it is not as simple as a simple drill bit.

And the difficulty of the build machine is like climbing to the sky. At least for New Kyushu, it's hard to climb.

Ma Jianbin convened the Institute of Physics to set up a shield machine team, and studied it for a month or two, but he didn't understand what the principle of the builder was.

Even the more I researched, the more I felt that the scientific truth here was simply strange. It seems like a simple digging a hole, why is it so difficult?

Ma Jianbin said: "Master Li, I'm afraid the shield machine is really not that simple. Because when we dig a tunnel, we are not dealing with a layer of soil, but a layer of rock. Tunneling through the rock is extremely difficult. The first thing we have to face is the design of the drill bit. ”

Li Zhen asked: "Is there any difficulty in designing drill bits?" ”

"The strength requirements of the drill bit can be met, but the style design of the drill bit is difficult. There are electric drills in New Kyushu, and we took inspiration from them to design the kind of drill bits with spiral and expansion patterns. But then we found out that it didn't work. The EPB is not such a thing as a large drill at all. You can easily use an electric drill to punch holes in wood, even in metal. But you can't punch holes in the stone.

Stone is not the same as other substances. It's going to shatter when it gets shaken at that high frequency. If a large electric drill is placed in the rocky mountain to excavate, then if it is not done well, it will directly be a landslide and ground crack. Security issues have been greatly troubled. Therefore, the shield machine is by no means as simple as a large electric drill. It should have some way to achieve a stable equilibrium that can make holes in the stone, but not crack the stone. ”

Li Zhen nodded, feeling a little difficult in his heart.

Zhang Zhi also found some information for him from the Internet for his reference, but Li Zhen did not fully understand it. That thing was also a high-tech technology in Zhang Zhi's time, and even many countries needed to import it. I can't produce it myself.

Li Zhen said: "There should be two aspects that cause cracks in the stone......

Before Li Zhen finished speaking, Ma Jianbin interjected: "High-frequency vibration, and expansion development. ”

The so-called expansive development, this is a word invented by Ma Jianbin and them, which means that the drill bit is conical, the front is sharp, and the back is thick. It's like a wedge. The front side gets in, and the back side is hard to squeeze in, which causes expansion and expansion, and it will crumble the hard stone.

"Yes, for those two reasons. Therefore, the design of this drill bit should meet the rigid requirements of two aspects. ”

"What?"

"One is that the speed of the drill bit is not large, but the torque is high. The second is that the drill bit must be cylindrical and parallel. It is very simple to meet the first requirement, but the second requirement is relatively difficult, and that is that the contact surface between the drill bit and the mountain is large. And the front must not be pointed, it must be flat. ”

Ma Jianbin smiled bitterly: "That's right, Master Li, we also found this problem." We made a cylindrical drill with a completely flat front to punch holes in the stone. This completely flat drill bit rotates at high speed in a way that grinds stone, and it actually cuts a hole in the stone that is extremely smooth. The structure is fully formed. But ......"

"But what?"

"But do you need such a drill bit to dig a tunnel? Without any scientific and technological content, just a solid cylinder with a diameter of a few meters, or even more than ten meters? That's impossible. A drill bit with a diameter of a few centimeters and punching holes in a stone is not of the same grade as a drill bit with a diameter of nearly ten meters to punch holes in a mountain. First of all, a solid cylindrical rotor with a diameter of more than ten meters weighs at least a dozen tons, and our science and technology are completely incapable of making such a drill bit rotate at high speed.

If a mechanical principle is used, it produces a high-torque, low-speed rotation. The speed of the drill bit can only reach tens of revolutions per minute, or even more than ten revolutions. Such a low speed is completely as efficient as dripping water through stones. It's not as fast as blasting and hand-made. Moreover, even if we have the ability to produce such a powerful engine, even if we have a drill bit with a diameter of 10 meters, the same high speed as an electric drill. Then the vibration caused by the weight of more than ten tons of drill bits will increase exponentially, and it is not a problem to collapse a mountain. ”

Ma Jianbin sighed deeply: "So, it's difficult." ”

Li Zhen smiled: "Actually, it doesn't hurt to think differently. What if the front end of a large flat drill bit with a diameter of several meters is set up with hundreds of small drill bits rotating at high speed? ”

"What do you mean?"

"The principle of the whetstone. The principle of using a flat drill to remove the diamond head is the same as that of a whetstone, not to drill through the stone, but to grind the stone through. But you just want to add sand and roughness to the flat drill bit to increase friction. Why can't we think about how to increase this friction by hundreds of times? Imagine if the large drill bit rotates slowly, and the side in front of the drill bit that is in contact with the mountain, there are hundreds of small drill bits that rotate in the opposite direction, or rotate along the trend. So will the friction increase by a hundredfold, a thousandfold? ”

Ma Jianbin's eyes suddenly lit up, and he stood up suddenly, standing too violently and hitting his head against the wall, he couldn't care about the pain, and exclaimed: "Is that so?" yes, why didn't I think of that? Master Li, you are simply the light that God has given to this world. ”

"That's right. In the process of slow rotation of a main drill bit, hundreds of small drill bits that rotate at high speed are attached to the main drill bit, which is equivalent to hundreds of people using hundreds of electric drills equipped with that kind of grinding stone drill bits to dig tunnels by hand? A mountain cannot withstand a large drill bit that rotates at an ultra-high speed and emits ultra-high vibration frequencies. But it can definitely withstand hundreds of small electric drills grinding on it. The vibrations of a small electric drill are incalculable for a mountain. ”

"Master Li, you're a genius!"

Li Zhen smiled: "I just put forward an idea. But there are many difficulties in the specific design that you need to overcome. Or even insurmountable. I don't know if you have the ability to do this kind of process, in a drill bit that is already rotating, in the design of hundreds of small drill bits that rotate at high speed at the same time inside the drill bit, it is a headache to think about. ”

"It's a great idea. You said that going from zero to one is the hardest, but going from one to one thousand is the easiest. Everything is difficult at the beginning, and now we have an idea, at least we know in what direction to go from. It's a step to the top! ”

Ma Jianbin was excited and ecstatic.

Others followed suit.

This kind of excitement and ecstasy that has broken through the intellectual barrier in the midst of scientific predicament is something that ordinary people cannot experience.

To express this sentiment in a slang phrase, it is:

Compared to love, it makes people feel more happy and excited.