Development of productivity started in 1981

Chapter 273 High-speed rail inspection and preparation for introduction

"Hello, could you tell us about this bridge crane?"

At a construction section of the "Mi-Yang" high-speed railway, a bridge expert from China looked at the section of road under construction not far away and asked the engineering staff from the Quanjiezhen who were accompanying him.

They had only seen some reports in foreign engineering magazines and related newspapers before, and knew that some developed countries abroad had abandoned traditional methods when building bridges.

Instead, prefabricated box girders are used, and then the prefabricated girders are placed on the hardened bridge piers by crane or bridge-building machine.

The advantage of doing this is that it can greatly reduce the construction period of the bridge.

For example, the construction of prefabricated box girders can be carried out simultaneously with the construction of bridge piers or even in advance, and the two are not restricted by the construction procedures.

The traditional method requires waiting until the bridge piers are cast and hardened before building the formwork upwards along the piers as support, then tying the steel bars, and finally pouring the cement.

This method is really time-consuming, and the construction period must be during a period of little rain. Sometimes, after the steel bars have been tied, if it rains continuously, the steel bars need to be protected to prevent rusting, and then the concrete can be poured after the rain stops.

In addition, the manufacturing cost of prefabricated box girders will be much lower than traditional methods. After all, when prefabricated on a large scale, they can be carried out in certain places suitable for transporting raw materials such as cement, sand, stone and steel bars.

Those templates can also be reused and require almost no handling.

When manufacturing this type of railway bridge using traditional methods, a lot of construction materials have to be transported across rugged terrain, which is very costly.

"Of course, the leader has already told us that we will do our best to answer all your questions regarding engineering construction and equipment use."

"Thank you very much. Don't worry if you laugh at us, but we have never seen this kind of bridge-laying machine in person before. We have only seen photos of it."

"It's okay, I'll explain it to you right away."

"Our bridge-erecting machine is a double-arm bridge-erecting machine, which is the core equipment for erecting prefabricated beam segments. Its working process combines mechanical mechanics with automatic control technology, and can accurately position hundreds of tons of concrete beams in complex terrain."

“Its general workflow is
Beam transportation and beam feeding: The precast beam is first transported to the tail end of the bridge erection machine by the beam transport vehicle, that is the engineering vehicle at the back that is pulling this precast beam.

The front legs of the bridge-building machine will then adjust their height through the hydraulic jacking system so that the main beam track can be docked with the beam transport vehicle track.

The beam transporter then pushes the beam into the belly of the bridge erecting machine at a speed of 0.5-1.5 km/h. The front beam lifting trolley locks the beam head, and the rear beam lifting trolley follows synchronously to ensure that the beam is subjected to horizontal force. "

“Beam lifting and longitudinal movement: The hydraulic winches of the front and rear beam lifting trolleys are activated to synchronously lift the beam to the top of the main beam track at a rate of 0.5 meters per minute.

The main beam is driven by a hydraulic motor to drive the rack and pinion system, moving longitudinally along the pier at a speed of 3 meters per minute.

At this time, the middle legs and the rear legs alternately anchor the bridge piers, forming a "three-point support" to ensure stability.

“Transverse positioning: When the main beam moves to the top of the target pier, the transverse mechanism is activated.

The transverse trolleys on both sides drive the rollers through variable frequency motors, adjust their positions on the transverse tracks with millimeter-level accuracy, and cooperate with the laser positioning system to correct lateral deviations.

At this time, the beam suspension height is kept 50 cm from the top surface of the pier to facilitate fine-tuning.

“Beam drop and anchoring: The hydraulic system controls the hanger to drop at a slow speed of 0.1 mm/s. After the bottom surface of the beam contacts the rubber bearing of the bridge pier, the pressure sensor provides real-time feedback on the load distribution.

When the pressure difference at the four corners is less than 5%, the prestressed anchor tensioning equipment is started to fix the beam end with a preload of 800 kN to complete the single-span erection. ”

The leader of the construction section of Quanjiezhen gave a detailed explanation to the domestic bridge experts based on the data that can be mobilized by the brain-computer chip.

There were very few pauses during the process, which showed that he was very professional.

This made several bridge experts unable to stop taking notes.

Originally they thought that the construction manager on the site knew very little and might only give a brief account of the situation, but they did not expect that the employees of the engineering construction company under Quanjie Zhen were so professional.

Thinking of this, several experts were moved again.

At this time, the country was also carrying out large-scale construction, but only some national key projects were guided by engineers who graduated from professional schools, while other projects were basically managed by makeshift teams.

Some retired experts in their 7s and 80s have to go to the front line to help oversee some key processes.

However, construction accidents still occur very frequently. To be honest, the quality of some projects is barely up to standard, and their service life is limited to the minimum standard.

This situation has gradually improved in the past two years, and graduates from some professional colleges have begun to graduate one after another.

After another 1 or 2 years of intensive on-site training, we can at least ensure that most of the key projects can be constructed according to the design standards.

"Hello, have you memorized all this information?" a bridge expert couldn't help but ask curiously.

"Well, we do have professional training, and we've basically written down everything." The engineer from Quanjiezhen scratched his head and said pretending to be embarrassed.

In fact, it is not wrong. The brain-computer chip can access technical content within its authority at any time, just like remembering it by itself.

"It's amazing! You watch the construction on the site all day long, attend training, and remember so much professional content."

"Okay, shall I continue the introduction?"

"Okay! Please speak slower, we can't write as fast as you do!"

"Then I'll speak slower. What I just talked about was the working process of the bridge-building machine. Now I'll talk about the core technical principles of this bridge-building machine. Many technologies are unique to us and are more advanced than those of Germany, Japan and Italy." The engineer boasted about his own bridge-building machine and then continued to introduce it.

“The first is the use of self-balancing structural mechanics technology: the bridge-building machine adopts a "double main beam + three legs" space truss structure. The main beam is welded from Q345B high-strength steel plate into a box-shaped section with a bending stiffness of 1×10 kN·m.

The front and rear outriggers use a hydraulic synchronous control system to achieve dynamic load distribution, ensuring that the maximum load-bearing capacity of a single leg does not exceed the design value (usually 1 tons).”

“The second technology is multi-degree-of-freedom coordinated control: the PLC (programmable logic controller) integrates a sensor network to monitor the height difference of the hanging point (accuracy ±2 mm), track deviation (±1 mm) and hydraulic pressure fluctuations in real time.

The PID algorithm is used to adjust each actuator to achieve a three-axis motion error of less than 3 mm for longitudinal movement, lateral movement, and take-off and landing.

“The third item is the anti-overturning safety design: under the condition of level 8 wind load, the gravity counterweight (accounting for about 30% of the total weight of the machine) and the pre-embedded shear keys in the piers work together to resist the overturning moment.

When the wind speed exceeds 15 m/s, the anemometer triggers the emergency brake and the bridge erector automatically switches to the rigid anchoring mode.

"How is it? Have you written everything down?" After the engineers from Quanjiezhen finished their explanation, they specifically asked several visiting experts.

"** Engineer, what is this PID algorithm?"

"This is a computer program that our software team wrote for this bridge-building machine. I don't know the specific content of the program, but its function is to adjust the errors of the various actuators as I just mentioned."

"Computer program? This kind of equipment is controlled by computer? Don't the staff adjust the parameters manually?" the expert from China asked in surprise.

At this time, only some imported large-scale engineering equipment in China had computer control, but the computers were still very simple, just changing some of the buttons that workers used to press manually to computer control. "That's right! Most of our engineering equipment is equipped with computers and air conditioners. For example, this bridge erection machine has a BIM model that pre-simulates the bridge linear parameters, generates a beam erection trajectory file and imports it into the control system, reducing on-site adjustment time by more than 30%."

The engineer said some incomprehensible professional terms, which made the domestic experts very embarrassed.

But their professionalism allowed them to remain calm and continue asking each other questions they didn't understand.

The engineers of Quanjiezhen tried their best to answer what they could. As for some contents that were not related to his major and he was not supposed to understand them, the system would not give him the permission to view them. He would just honestly say that he did not understand and could ask other people in related majors.

A similar scene was also happening in another tunnel construction section.

Several tunnel engineering experts were shocked to see Myanmar using a tunnel boring machine with such a large diameter (13 meters).

They had actually seen and even used it as early as the 60s.

It was introduced from the Soviet Union at that time.

However, that type of equipment is mainly simple machinery (such as hand-dug shield), and is mainly used in test sections of urban underground engineering.

For example, it was used in the early experimental projects of Shanghai Metro.

Its diameter is only more than 4 meters, and its efficiency is not much higher than the traditional drilling and blasting method. Sometimes when encountering certain terrains, we have to switch to traditional methods for construction for a section.

A few years ago, the Wanjiazhai Yellow River Diversion Project in Shanxi Province introduced the American Robbins double-shield hard rock TBM to cross the hard rock formations of the Luliang Mountains, but it was discontinued midway due to geological adaptability issues.

The diameter of that shield machine is only half of this one, and its working efficiency is much lower.

Seeing such a large working face, several experts couldn't help but care about its excavation speed. If the speed is also very fast, then it would be very necessary to introduce this kind of equipment into the country.

"Hello, Engineer **! What is the tunneling efficiency of this shield machine?"

"The average daily progress of this equipment is: 20-40 m in soft soil and 5-15 m in hard rock."

"So fast? It's several times faster than traditional blasting methods." The domestic expert who asked the question exclaimed.

"We have to work so fast to catch up with our planned progress. Are you still using traditional blasting methods for construction?" The staff member of Quanjiezhen asked curiously.

He is a traditional Burmese. The older generation had told them about China and described them as the Celestial Empire, so in his impression, China is very powerful.

"Haha~, yes! But we are importing this type of shield machine. I wonder if your model can be exported?"

"Ah? I really don't know. I only know how to use it and what technologies are used. For export, you should ask our relevant departments, such as the foreign trade department."

"Okay, can we go inside and take a look at the construction?"

"Sure. Put on the helmet first. Also, you have to receive training and learn the precautions. You can't move around or touch the buttons inside."

"Okay, no problem, we'll just watch and never do anything."

Next, several experts received a 20-minute training session and then, accompanied by relevant personnel, walked into the operating tunnel boring machine.

It moves forward segment by segment like a giant caterpillar.

Every movement of one section represents an advance of 1 to 2 meters.

The various tubes inside are just like the intestines and esophagus of a caterpillar.

The cutting disc in the front acts like the teeth of a caterpillar, crushing the soil and rocks.

Then the crushed rock sprayed with water or the soft soil sprayed with foam is transported to the rear vehicle by a belt conveyor and a mud pump.

Several domestic experts expressed their feelings as they walked.

Walking inside such a large tunnel boring machine feels like walking in a big house.

Although various equipment were rumbling and the noise of rock cutting was rather harsh, it sounded so familiar to the experts.

Several people walked until a few meters behind the cutting disc before stopping at the signal of the staff.

Seeing the huge blade that was taller than a 5-story residential building, the few people were very shocked.

The blade does not rotate very fast, about 5 revolutions per minute.

The huge cutting head is larger than an adult, and the black protrusions are the teeth of this giant caterpillar, chewing up the rocks in front.

The working noise inside is reduced by the active noise reduction system, allowing them to communicate while wearing headphones.

They asked questions as they watched, and the staff on site gave very professional answers.

Several survey teams that went to the "Mi-Yang" high-speed railway recorded in several notebooks every day. After returning to their base, they borrowed notes from each other to avoid omissions and errors.

Three days later, several expedition teams met in Mandalay, the capital of Myanmar at that time.

They reported the investigation results to a vice-chairman of the leadership, hoping to introduce the high-speed railway and a full set of construction equipment from Myanmar.

Considering the domestic economic support capacity at that time, they suggested whether they could learn from Myanmar's practice and build an experimental high-speed railway first.

"Build an experimental high-speed railway? Our current four horizontal and four vertical conventional railways have not been completed yet. Wouldn't it be a waste to build this kind of high-speed railway?" the leader asked.

“We are hoping to revise the railway master plan.

Instead of building some railways that are mainly passenger lines, it is better to directly build this kind of high-speed railway.

Railways whose main function is freight can maintain their original construction plans, but must be prepared for future speed increases.

We all think that high-speed freight trains will be able to mature in the future. Although they cannot run at 3 or 4 kilometers per hour like passenger lines, speeds of 120 to 180 kilometers per hour are possible.”

"Well, I understand your suggestions. You can organize relevant experts to submit a report and then discuss it at the meeting.

During the inspection, I authorize you to discuss certain technology introduction issues with the Quanjiezhen side. I will have the relevant negotiation experts coordinate. You will take the lead in technology, and the conditions will be based on the opinions of the negotiation experts. Pay attention to mutual cooperation. "

"Okay, we'll go back and write the report and prepare for the technology introduction."

After the railway inspectors finished their report, another group of steel industry experts also completed their inspection and were waiting to be received by the head of the delegation.

(End of this chapter)