The story of the builders of Baihetan Hydropower Station: a decade of hard work

The world-renowned Baihetan Hydropower Station project, from its preparation to its commencement to construction, and then to its full completion and commissioning, has embodied the wisdom and hard work of several generations of Three Gorges people.

Some of them came from the hot construction sites of the Three Gorges Dam, Xiangjiaba and Xiluodu projects, and some came from university campuses. Batch after batch, generation after generation, they have worked for the dream of China's hydropower and also achieved the glory of hydropower workers.

Today, all the units of the Baihetan Hydropower Station have been put into operation to generate electricity. The rivers are rushing and the echoes are resounding, paying tribute to the builders with the sonata of mountains and rivers; the towering mountains, high gorges and flat lakes, with the solemnity of the sky and the earth, listen quietly to the stories behind the construction of this great project.

Aerial photo of the downstream side of the Baihetan Hydropower Station dam. Photographed by: Zhao Jian

Million-kilowatt units: the "Mount Everest" of world hydropower

Standing on the Baihetan Dam and looking into the distance, the dry and hot valley is surrounded by high mountains and steep cliffs, and a group of egrets are flying up and down the dam. In the mountains on both sides, there are 16 million-kilowatt hydroelectric generators with the largest single-unit capacity in the world installed in a spacious and bright underground plant, and the huge amount of electricity produced is transmitted to the eastern part of the motherland.

At the last critical moment when the unit was fully put into operation to generate electricity, a group of builders stayed at the site, and the final stage of the unit commissioning was proceeding in an orderly manner.

"Don't be fooled by the fact that everyone is so calm now. When the first unit was put into operation to generate electricity, my heart rate soared to 150!" Kang Yonglin, deputy director of the Baihetan Project Construction Department of the Three Gorges Group, pointed to the sports watch on his wrist, which showed that his heart rate was 70 at the moment.

All things are difficult at the beginning. From 0 to 1 is a qualitative change. The most difficult thing is to put the first unit into operation and generate electricity.

A single unit of the Baihetan Hydropower Station is 50 meters tall and weighs more than 8,000 tons, which is as heavy as the Eiffel Tower. Before the trial run, the unit had never been turned. Scientific theory proves that it can turn, but that is only theory. No one can guarantee the actual situation.

What does it mean to be successful for a million-kilowatt unit? It is only when all commissioning is completed and a 72-hour trial run is achieved that a million-kilowatt unit is successful.

Kang Yonglin still clearly remembers that when the first unit completed 72 hours of trial operation and was announced to be officially put into operation, he did not even dare to go up to the unit to take a look.

"At that time, everyone present was very excited when they heard the sound of it turning. The significance of this is really too great!" said Kang Yonglin.

The successful commissioning of the first million-kilowatt unit means a breakthrough from 0 to 1, and the next 15 million-kilowatt units will be put into operation in succession.

All units of Baihetan Hydropower Station have been put into operation. Photo: Zhao Jian

During this process, the Baihetan Hydropower Station's million-kilowatt units also attracted the attention of the hydropower industry, and experts and scholars from the industry came to visit.

"I remember there was an old dean who was already 85 years old. When I met him, I was still a young man. He had come here before and asked me about technical problems that I had not been able to solve in the past but had already been solved at the Baihetan Hydropower Station," said Kang Yonglin. When talking about these topics, he gestured from time to time and told reporters about the various technological innovations of the Baihetan Hydropower Station.

Take stator vibration as an example. When the unit is running, the stator frame is subjected to complex forces. If the frame vibrates greatly for a long time, it will damage the stator core and wire rod insulation, which has a significant impact on the life of the unit. "During the electromechanical installation process, we controlled the stator roundness, rotor cylindricality, and rotor eccentricity to the optimum, but the stator frame vibration was still too large during the unit commissioning." Kang Yonglin said.

After discovering this problem, Kang Yonglin led the team to analyze the factors from three aspects: hydraulic, mechanical and electrical. They conducted a detailed analysis of the rotor lamination process, magnetic pole weight, roundness, generator air gap, guide shoe gap, guide bearing swing, guide bearing bracket horizontal and vertical vibration and other data. It turned out that after the unit was overspeeded, although the roundness and air gap of the stator and rotor met the quality standard requirements, there was a slight deviation in the distribution of the gap between some adjacent magnetic poles, resulting in large vibration of the stator frame. Find out the crux of the problem, take effective measures and finally successfully control the vibration amplitude to the excellent standard, which has become a must-talk case every time he gives a speech.

"Since you dare to be the first to try something new, there will definitely be many problems that require you to cross the river by feeling the stones. When you encounter difficulties, you must face them head-on and dare to fight. As long as you are willing to think and study, there will definitely be a solution in the end." Kang Yonglin told reporters.

Underground caves: an "underground palace" that can be called a work of art

In books, we can find descriptions of the importance of mountains and rivers everywhere; in movies and TV series, in a series of doomsday movies, humans have built their last shelter deep in the mountains. The mountains are heavy, solid and silent, but they give humans the last sense of security.

Today, literature and art have become reality. On both sides of the Jinsha River, there are hundreds of thousands of mountains, and in the mountains on both sides of the Baihetan Hydropower Station, there is an "underground palace" hidden, which is the "home" of the million-kilowatt unit of the Baihetan Hydropower Station.

The car drove through the mountain, which was like a maze of underground traffic tunnels. Rows of bright light strips, silver-gray cave walls, and cold steel pipes, this is the world of industrial heavy metal, a "man-made wonder" that countless artists rarely see in their lifetime.

"Now it seems that this underground factory building can be called a work of art, but when it was being built, it was extremely difficult." Duan Xingping, head of the underground factory building project department of the Baihetan Engineering Construction Department, told reporters.

This "underground palace" is the world's largest underground cavern complex, with a total length of 217 kilometers, equivalent to the length of four Hong Kong-Zhuhai-Macao Bridges. The excavated volume of the caverns is 25 million cubic meters, which can fill 10,000 international standard swimming pools.

In order to accommodate these 16 million-kilowatt units, a "bedroom" 438 meters long, 34 meters wide and 88.7 meters high was dug on the left and right banks of the Baihetan Hydropower Station. This huge space dug out in the mountains on both sides can accommodate an aircraft carrier each.

Main Factory Building on the Left Bank of Baihetan Photographer: Xie Lei

Main factory building on the right bank of Baihetan Photographer: Xie Lei

The world-class scale corresponds to the world-class construction difficulty. The underground caverns of Baihetan Hydropower Station are located in the Hengduan Mountains. There are obvious columnar joints and many cracks between the rock layers, making the deformation and stability of the surrounding rock even more difficult.

"At that time, our biggest pressure was the stability of the surrounding rock of the cavern group and the safety risks that might be caused by abnormal situations," said Duan Xingping.

The Three Gorges Group attaches great importance to the safety assurance of the Baihetan Hydropower Station construction project. During the peak period of underground plant construction, Duan Xingping and his team stayed on site day and night, discussed plans with all participating units day and night, and consulted experts in turn. Through the combined efforts of various measures, the safety risks were finally reduced to a minimum.

"I remember staying at the construction site for several Spring Festivals to carry out emergency rescue and reinforcement." Duan Xingping recalled that during the excavation of the underground factory building, construction could not be interrupted and he and his colleagues took turns to be on duty at the site. "Even when I occasionally went back for vacation, I was still worried about me staying at home."

During the years of construction and Spring Festival duty, the "home" of the million-kilowatt unit was finally built.

Foundation grouting: "Sunshine Dam" under concealed engineering

The Baihetan Hydropower Station is located in the Jinsha River Gorge. The dam foundation is mostly columnar jointed basalt, which is like a bundle of upright "chopsticks" and becomes loose and brittle after stress release. If you want to build a 289-meter-high dam on it, the grouting project is extremely important. It is not only a technical job, but also a "conscience job".

In the hydropower industry, grouting projects are called "hidden projects". Workers carry out construction underground, and the grouting is also poured into the ground or the dam body. It is impossible to see whether the work is done well or not. Even if it is later discovered that it is not done well, the cement slurry has already been poured in, making it difficult to rework.

"The previous grouting engineering industry was like 'seeing the leopard through the tube', only seeing part of it but not the whole picture." Wang Kexiang, deputy director of the dam project department of the Baihetan Project Construction Department, pointed to the grouting photos on the wall and patiently explained to reporters.

Wang Kexiang said that in the construction of the Baihetan project, quality problems in "hidden projects" were absolutely not allowed. To this end, he and his team thought of various ways to make the grouting work a "sunlight" project.

The first step is to carry out integrity education. In conjunction with the Party building work in the Baihetan construction area, the design, construction, supervision and other units are united to take an integrity oath, and the sense of responsibility of the builders is enhanced through the ceremony.

Secondly, we should make the "hidden project" open to the public. At the construction site, we set up a cultural corridor for grouting workers. In this corridor, those who do a good job will become grouting models for others to learn from and refer to, and those who do not do a good job will become samples for summarizing their experience and lessons.

Finally, it is to improve the professional image. In the past, grouting workers often gave the outside world an impression of being "dirty, messy and poor" in their grouting work clothes, and many workers had a low sense of professional identity. To change the professional image, we must first start with improving the working environment. The Baihetan construction site promotes "standardized" construction, rejects "dirty, messy and poor", and strives to do "civilized construction".

The oil industry has its own song for oil workers, and the exploration team has its own song for exploration team members. Why can't the grouting industry have its own song? Wang Kexiang thought about it again and again, and finally joined hands with the grouting construction unit to create the "Song of Grouting Workers" to enhance everyone's sense of professional identity.

Facts have proved that these measures have indeed played a very good effect. The Baihetan Dam concrete pouring reached 2.7 million cubic meters per year, with a monthly peak of 273,200 cubic meters, creating the fastest concrete pouring speed for dams of similar projects, and a high-quality dam was built under such rapid construction.

"The construction efficiency and quality of the Baihetan Hydropower Station project are the fastest and best in the projects I have experienced. We initially thought it was an impossible task, but now it seems that we have completed it," said Li Yongjun, a member of the Production Department of the Baihetan Construction Bureau of the Fourth Hydropower Bureau. Li Yongjun is an old hydropower worker who has participated in the construction of many hydropower projects. During the peak period of Baihetan Dam construction, he led his team to set a record of grouting more than 12,000 cubic meters in 24 hours.

Today, standing on the Baihetan Dam, the cable crane group responsible for transporting concrete for the dam's pouring is being dismantled. The sunlight shines directly down, giving the surface of the dam a golden color.

"In May 2021, I was on night shift when the last batch of concrete was poured for the dam. Seeing the completion of the pouring of the dam, I felt complicated and mixed emotions, but I was very happy." Pei Lei, an engineer from the Baihetan Construction Department, stood on the dam, his tone full of pride.

Ultra-high arch dam: a seamless dam that does not leak water

Looking out from the Baihetan Dam, the water storage height has reached 825 meters. A flat lake appears in the high gorge, the sky is blue and the river is clear. The reservoir area is peaceful and tranquil.

For ordinary tourists, the dam has become a window to showcase the Baihetan Hydropower Station to the outside world. However, in the eyes of dam construction experts, the quality of the dam and whether there are cracks in the concrete are the key.

"Temperature control and crack prevention are one of the most important quality control links in the construction of hydropower dam concrete." Standing at the Sichuan-Yunnan boundary on the dam, Zhou Mengxia, deputy director of the Technical Management Department of the Baihetan Project Construction Department, told reporters while touching the dam guardrail. He is the main person in charge of the concrete temperature control technology of the Baihetan Dam. "Concrete temperature control, in layman's terms, means that cement hydration will generate heat, and the thermal expansion and contraction will cause the concrete structure to deform, which can easily lead to deformation and cracking of the dam."

Traditional concrete temperature control is very cumbersome. Cooling water pipes are buried in the poured concrete dam body. During the cooling process, the temperature is collected every three or four hours. A large number of on-site workers are required to collect data and then summarize and analyze it. The water flow regulation of the cooling water pipe also relies on manpower, which is time-consuming and labor-intensive, and the response is often delayed.

With the advancement of science and technology, various advanced information technologies and automatic control equipment have been applied in Baihetan and integrated with the construction of hydropower projects. The dam project also fully applies the intelligent construction system. Today, a "smart" dam has been built. "With the development of science and technology, we apply the latest scientific and technological achievements to engineering practice." Zhou Mengxia said.

In the temperature control of the Baihetan Dam, digital thermometers replace manual labor. These thermometers buried in the dam body monitor the temperature changes of each warehouse of concrete in real time, and upload them to the server in real time through the wireless network. The server analyzes the temperature change trend through big data and temperature control theory, calculates the water flow rate required for subsequent temperature control, and adjusts the water flow rate in the cooling water pipe through the solenoid valve.

Workers at the pouring site use their mobile phones to check and record pouring information. Photo: Huang Chunjiang

"This is a very sophisticated implementation, which is a huge improvement over the previous traditional temperature control technology," said the on-site staff.

Technology solves one aspect, but there is still a lot of work to be done manually at the dam temperature control site.

From the beginning of the dam pouring, the cooling water pipes used for cooling will begin to be laid. The construction temperature of the Baihetan Dam in summer often exceeds 40°C. After the concrete is poured, the cement will react with water and generate heat. It is a big challenge to control the concrete temperature within the design standard range in the dry and hot valley environment.

From the pouring of the first chamber of the dam in March 2017 to the pouring of the dam to the top on May 31, 2021, Xu Anwei from the Baihetan Construction Bureau of the Eighth Hydropower Bureau has been responsible for the temperature control construction of the concrete of the right bank dam. He said: "We adopt a refined operation, dividing the personnel into several teams such as laying water pipes, flow control, and temperature control equipment maintenance, and carry out temperature control operations in batches and in an orderly manner."

Baihetan Hydropower Station is located in the Jinsha River Gorge. In the low temperature season, the temperature drops frequently and there are many strong winds. The newly poured concrete needs to be carefully insulated. At two or three o'clock in the night, there are often strong winds on the dam, with wind speeds reaching more than level eight, which will lift the insulation blanket. Zhou Mengxia and the dam construction team insisted on night duty, climbing over 31 undulating dam sections, checking the construction quality of every corner of the dam, and ensuring that the insulation blankets in every place were completely covered.

"It took a total of 1,511 days from the pouring of the dam to its final completion. During these 1,511 days, neither I nor anyone in the team slacked off for a single day," said Zhou Mengxia.

Flood discharge tunnel concrete: "mirror concrete" that reflects people's shadows

On the left bank of the Baihetan Hydropower Station Dam, three giant flood spillways are dormant in the mountain, waiting for the dam to open and transform into giant dragons "spitting water".

"Nowhere in the world has a flood discharge tunnel of this quality been built, but we have." Wang Xiaohai, director of the flood discharge tunnel project department of the Baihetan Project Construction Department, gently stroked the smooth wall of the flood discharge tunnel. At this moment, the ground wall was like a mirror, reflecting his figure in work clothes.

This quality standard of concrete that can reflect a person's shadow is called "mirror concrete" in the hydropower industry. It has precise shape, is flat and smooth, wear-resistant and crack-resistant, and presents a mirror effect under water flow maintenance.

The completed flood discharge tunnel. Photo by: Xie Lei

Other places have not been built, why was Baihetan built?

Wang Xiaohai gave the answer: "I have already said too much about the technical aspects, so I want to say something different. Maybe we are a group of 'serious' people. If we want to do something, we must be the first and do it to the extreme."

As the main person in charge of the flood discharge tunnel project, Wang Xiaohai is "quite famous" on the Baihetan construction site. Some people say that he is a relatively "stubborn" person who will focus on details and polish them repeatedly until the highest standards are reached.

"I used to work in unit maintenance, and mechanical maintenance is also a meticulous job, so I applied some of the practices in mechanical maintenance to concrete." Wang Xiaohai said confidently.

From the beginning to the end, all concrete construction of the flood discharge tunnel project was carried out in accordance with strict process steps, which gradually changed the workers' habits, thinking, and "habitual" practices, even down to the precise hand movements during pouring.

There are many factors contributing to the success of the "mirror concrete" of the flood discharge tunnel, but Wang Xiaohai's extraordinary "axis" may be one of the important factors for their success.

There is a rumor in the Baihetan construction area that Wang Xiaohai can tell with his naked eyes whether the construction of the flood discharge tunnel is up to standard or not. Now, this rumor has been confirmed by him.

"That's true. I can tell at a glance the flatness: 2 mm, 2 mm. If you pick up an unqualified concrete sample from the site, I can tell you why it is unqualified." Wang Xiaohai's tone was full of conviction.

Such confidence comes from his deep research on flood discharge tunnel construction technology. The Baihetan flood discharge tunnel project is like a "database" and Wang Xiaohai is a "data analyst". In this database, Wang Xiaohai can see all the mysteries behind it.

In the Winter Olympics short track speed skating event, champion Wang Meng once said, "My eyes are a ruler." Now it seems that Wang Xiaohai, in the flood discharge tunnel project, his eyes are also a ruler.

postscript:

During the interview, I asked these builders what the Baihetan Dam meant to them, and all of them answered in unison: pride and growth.

Looking around the world today, no other place can provide such a huge career platform for hydropower builders. Here, they are full of high spirits and work enthusiastically to create glory for China's hydropower industry.

When asked about their future career plans, all of them answered: If there is another opportunity like this, we would like to work for a few more decades until retirement.

If a profession can provide builders with infinite sense of pride, it proves that it is a great profession. Everyone in this profession is radiating the shining points of being a human being.

At the end of the interview, I would like to revisit the words in General Secretary Xi Jinping’s congratulatory letter to the commissioning of the first batch of units of the Baihetan Hydropower Station: Socialism is achieved through hard work, and the new era is achieved through struggle.

This is the highest evaluation of contemporary Chinese hydropower workers represented by the builders of the Baihetan Project.