Beijing Subway Line 4 train in the 13.5-meter-deep underground, 100 meters away from the Peking University School of Information Science and Technology building, an electron microscope, "as if a hurricane".
With the naked eye, the 1-meter-high white metal cylinder stands firmly on the table. It will be adjusted to the highest precision, but will find that the black and white image on the display has grown "burrs", the original delicate atomic patterns because of the vibration has become blurred.
On the Peking University campus, the subway operation was affected by the precision instruments, far more than this multi-million dollar electron microscope. 4 line opened, Peking University has 1.1 billion yuan worth of precision instruments, of which 400 million yuan of instruments were affected.
In order to reduce the subway vibration interference on these instruments, Beijing and Peking University have made great efforts. In the east gate section of Beida on Line 4, the subway company laid state-of-the-art vibration-reducing tracks. Peking University specializes in the farther side of the new comprehensive research building, transferred some of the precision instruments, but the impact of subway vibration is still difficult to eliminate. Some scholars can only do experiments in the middle of the night after the subway stops running.
In 2019, 600 meters away from the comprehensive research building of the subway line 16, phase II of the entire line will be opened, NU within the precision instruments will face the dilemma of two-sided attack. Zhang Zhiqiang, director of the Environmental Protection Office of NU's Laboratory and Equipment Management Department, believes the situation will not be optimistic if more vibration-dampening measures are not taken.
Faced with subway vibration interference in scientific research units more than Beida. The reporter learned that Tsinghua University, the Chinese Academy of Sciences, Fudan University, Nanjing University, Capital Medical University, Zhengzhou University School of Medicine has also encountered similar difficulties. University of Science and Technology of China, Zhejiang University, Nantong University around the upcoming construction of the subway.
The increasingly dense subway network in the city, scientific research institutions more and more sensitive precision instruments, are China's rapid economic and social development of the sign. But when the high-precision instruments meet the subway line, who should be avoided, has become difficult to reconcile the contradiction.
The planned 2020 Beijing subway line network.
The butterfly effect of subway vibration
A subway track is growing rapidly in Beijing. By 2020, they will total nearly 1,000 kilometers. At peak times, nearly 1,000 trains will be speeding along the tracks at the same time.
While carrying passengers, these trains, which weigh more than 100 tons, have become a huge source of vibration. The vibrations spread like ripples through steel wheels, rails, tunnels and soil to the surface and into buildings.
Few people notice the impact this vibration has on cities. The Rail Vibration Damping and Control Laboratory at Beijing Jiaotong University was an early team to conduct the research in China. Data from their tests show that microvibrations in the ground within 100 meters of the subway in Beijing have increased nearly 10-fold in more than 10 years.
The intensity of microvibrations from traffic is not great, but they last a long time and their effects are hidden and not easy to detect. It has cracked and collapsed an ancient Czech church, chronically affected performances at the Bastille Opera House, and interfered with Intel Corp.'s ability to carve nanoscale circuits into integrated boards.
In the subway vibration, the most serious interference with precision instruments is low-frequency vibration. Such vibrations have long wavelengths and are not easily attenuated in the soil. Lei Jun, director of the Environmental Vibration Monitoring and Assessment Laboratory at Peking University, has been carrying seismometers with students, measuring many subway lines in Beijing, and they found that in the low-frequency range, which is more sensitive to precision instruments, the intensity of vibration on the surface within 100 meters of the subway is 30 to 100 times higher than when no train passes through.
The subway is almost a "catastrophic blow" to precision instruments at Peking University and Tsinghua University.
Before the subway opened, ambient vibrations caused by buses and railroads at two of China's most prestigious universities were approaching or even exceeding the safety values set for some instruments. However, most of these instruments are still functioning normally because of the margins left over from the ambient vibration requirements for normal use. Once the neighboring subway line opens, the vibration-sensitive precision instruments at the two universities will likely not work with the highest precision.
Some scholars argue that this is a huge waste of money, and that "the instruments that cost $1 million to buy back can only be used as $100,000".
Many users of the instrument do not realize that subway vibration affects the instrument. A colleague once found Lei Jun, complaining that a laboratory to measure the age of the rock precision instruments suddenly not normal. This teacher called the manufacturer, left and right adjustments, froze, can not be repaired, the manufacturer is also puzzled.
Lei Jun asked: "When did it start to be abnormal?" The other side said, "From 2009." In fact, it was not the instrument that was broken, but the vibration that interfered with the instrument after the opening of Metro Line 4.
"The total number of domestic experts studying subway vibration problems, including equipment manufacturers, is **** less than a hundred." Ma Meng, associate professor at Beijiao University, lamented that this is a very small academic circle, in which most experts are still in the same WeChat group.
For more than 10 years, Lei Jun has been calling attention to subway vibration problems on various occasions. As a member of the Jiu San Society, he has repeatedly written proposals to reflect the issue to the National People's Congress. Whenever he can, he popularizes the effects of subway vibration to uninformed scholars and students.
For a long time, he was originally engaged in seismology, but his mind was pushed into this cold academic field. His family used to tell him not to "go out of his way".
In Lei Jun's view, this field is quite important. He knocked on the table and asked: "China is experiencing industrialization transition, but why these years our scientific and technological achievements are large? Some of the core electronic components, including chips, photolithography, grating thin material and many other areas of parts processing, why even if we buy back a full set of foreign production lines, can not build the same thing? A big reason is the environmental vibration overload. Today we have been able to produce rough industrial products, our shortcomings are mainly in the precision, a small one can not be refined."
He has done environmental vibration assessments for two organizations. One is the China Academy of Metrology, is the country's highest metrological scientific research center, the original site of the environmental vibration seriously exceeded the standard, and then moved to Changping, the assessment but found that the new site still has some problems. Another is a national defense measurement station, environmental vibration exceeded more than 100 times.
To experts specializing in environmental vibration, the subway caused by micro-vibrations, seemingly a butterfly flapping its wings, but in the vibration-sensitive high-precision fields, enough to brew a catastrophic storm, thus restricting the development of a country: photolithography needs to be drawn in 1 millimeter thousands of lines, the need for the external environment to maintain extreme stability; high-speed rotating gyroscope in the missile system, the processing of the quality of the must be guaranteed! center and the geometric center completely overlap, otherwise it will point east and hit west.
The Peking University campus adjacent to the subway line on the map.
A lose-lose compromise
Like many outside scholars, Lei originally had no idea that subway vibrations had an effect on precision instruments. For the first time in China, Peking University's bitter struggle with the subway brought the issue to the surface.
In 2003, the Beijing Metro Line 4 program was announced, which would stick to the east gate of Peking University all the way to the north. Metro line on both sides of the close distribution of the University of several colleges of science and technology and many important laboratories, the University of a considerable part of the precision instruments are concentrated in these research buildings. Some scholars have reminded the university that it has to study whether the subway has an impact on precision instruments.
Lei Jun previously studied the building seismic, are the larger level of vibration, not much attention to the impact of micro-vibration. After starting to collect vibration data from other subway lines in Beijing, he realized that "the problem is very complex, much more serious than imagined".
Because of his and his colleagues' report, Peking University objected to Line 4 passing through. At the time, BYU and Metro argued repeatedly over two options: either BYU move the whole thing, or Metro Line 4 is rerouted.
Till the last workshop, the two sides remained deadlocked. The meeting was chaired by a Beijing vice mayor, who invited an academician and a number of experts from outside the university.
The academician said at the meeting that the track vibration isolation program is feasible. He drew an analogy with a program he had worked on, "Touch it with your hand, and the vibration can't be felt."
A representative of Peking University asked on the spot, "How sensitive is this sensor of the human hand?" Peking University is the most sensitive to vibration of that electron microscope, the sensitivity is hundreds of times the human body.
The meeting finally formed a resolution to adopt a compromise program - Line 4 through the University of North 789 meters of track section, will use the world's most advanced track vibration damping technology, that is, in the steel rail under the steel spring floating plate. Invented by a German company, the floating plate is a reinforced concrete slab about 50 centimeters thick, with steel springs underneath to isolate the train's vibration from the roadbed.
"For the train, this is equivalent to a very soft pad while the springs isolate the vibrations." Associate Professor Ma Meng of Beijing Jiaotong University told China Youth Daily? China Youth Daily Online reporter, this track vibration damping technology has reached its limit to a certain extent, and if it is softer, the safety of train operation may not be guaranteed.
This floating plate in general can be very good vibration isolation, but it also has a big disadvantage: due to the principle of vibration isolation, it is not much use for vibration below the self-oscillation frequency, and even likely to amplify.
After the opening of the Beida Dongmen section of Line 4 in 2009, Mamun and his colleagues conducted tests to verify the theory. In Mameng's opinion, the vibration-damping measures on this section of the track are still useful, ensuring that many less demanding instruments can be used normally, but for some extremely sensitive equipment, it can aggravate the interference.
NU was not satisfied with the results. Observations revealed that the old university hospital site to the southwest had slightly less vibration intensity. Peking University decided to build a comprehensive research building on the site and move some of the affected instruments over. However, due to site and financial constraints, only about one-third of the equipment could be moved in.
In 2011, with the foundations of the building already in place and construction underway on the lower floors, another piece of news arrived: subway line 16 would bypass the university's west gate, just 200 meters from the building.
Because there was no longer anywhere to move the precision instruments on campus, Peking University protested strongly. Lei Jun analysis, the reason for this embarrassing situation, because the subway company thought the damping was successful, and did not know that Peking University is planning to move the instruments. At the same time, they did not inform the planning program in advance of Beida.
Beijing allocated tens of millions of yuan of special funds, so that the General Administration of Municipal Affairs, Beijing Jiaotong University, China Electronics Engineering Design Institute, China Railway Research Institute and Peking University jointly formed a research project team to come up with a set of comprehensive solutions, in addition to subway track vibration damping, but also includes a redesign of the integrated scientific research building, to consider the installation of damping platform in the lower floors, the use of springs will be the whole of the building above the levitation up.
Lei Jun remembers those months, two or three days a week to meet to discuss, several parties often for specific programs to fight red in the face. An expert from an electronic design institute told reporters that the requirements of Beida were too idealistic, and that the two sides had different methods of collecting and analyzing data, leading to several times the difference.
An expert heard a joke: If this is not handled well, it will affect the University "impact Nobel Prize".
The project came to a screeching halt just as all sides were arguing. The story goes that the NU leader and a city leader met at a meeting and shook hands. Metro 16 took a step back, circling more than 300 meters to the west to get rid of two stations, and Peking University stopped making demands.
Yang Yikian, a researcher at the China Academy of Railway Sciences, is one of the experts on the project team. In his opinion, in this game, Beida seems to win, but it is not. It's not a perfect solution, it's a "lose-lose compromise".
Missing environmental standards
Yang Yiqian believes that the subway can reduce the interference with the precision instruments of the University of Beijing by taking a step back, but this distance is often not enough to eliminate the impact. On the other hand, the subway loses its ability to attract traffic when it is rerouted.
He suggested at the time that Peking University move its precision instrument buildings to the suburbs, thus eliminating interference altogether. But for many Peking University faculty members, such a suggestion was hard to accept. Yang Yikian could understand, after all, Peking University was built first, the subway came later, so whoever was asked to move would not be happy.
He and Lei agree that avoiding such a conflict should be a matter of first-come, first-served in planning. Newly planned subway lines should avoid vibration-sensitive high-tech areas as much as possible, and newly built high-tech zones should be located in suburbs without subways as much as possible.
The crux of the problem is that precision instruments are often purchased by research organizations first, but the impact is not taken into account in the formation of the subway planning program.
Yang Yiqian is familiar with foreign laws and regulations. Japan has a special Vibration Law. The U.S. rail transit environmental impact assessment standards involve vibration-sensitive equipment.
There have been lessons learned in both countries. The University of Tokyo had an entire building suspended AX by springs and still could not eliminate the vibration effects. The University of Washington in the U.S. used rail vibration dampening measures and reduced speeds due to a light rail line running through the campus, but five of the 15 sensitive buildings still exceeded the vibration limit.
"Vibration damping is a world problem, and the best thing to do now is to avoid it." Lei often cites the example of Japan's Tsukuba Science City. The city, which is home to a collection of Japanese research talent, was founded in 1963 and did not have a subway until more than 40 years later, and is 2.5 kilometers away from the same urban area.
China does not yet have an environmental vibration pollution prevention law, and while environmental protection standards include provisions on the impact of vibration on people in residential buildings, office buildings, hospitals and schools, they do not address interference with precision instruments. This has led to the subway planning program into the environmental impact assessment stage, the environmental protection department rarely consider this level.
Recently, the Ministry of Ecology and Environment issued the Technical Guidelines for Environmental Impact Assessment of Urban Rail Transportation (Draft for Comment), but still no mention of the impact of vibration on vibration-sensitive instruments.
Yang Yiqian also found that even environmental practitioners are divided on the issue. Some believe that the issue rightly belongs to the environmental protection department, while others are categorical that it does not.
The lack of evaluation criteria has led to ill-considered subway plans that pass through research institutes and industrial parks. A provincial capital city in the planning of the subway, in order to facilitate the travel of patients, deliberately set up a subway station in a university hospital, I did not expect to make some medical examination equipment can not be used properly.
It's often too late to identify potential problems. Once a specific subway proposal passes through the layers of approval, "it's almost impossible to move it out 100 meters".
This has often led to confrontations between universities and the subway. line 15 was originally planned to run through Tsinghua University, which was strongly opposed by Tsinghua. In the end, Line 15 only went 120 meters into the Tsinghua campus, and did not connect with Line 4 to form a transfer station.
As early as 1955, Tsinghua University had the railroad rerouted. The Beijing-Zhangzhou Railway is located on the same side of Tsinghua's campus, and vibrations had seriously interfered with research, so Tsinghua fought for the rail line to be moved 800 meters to the east.
Not all universities have strong negotiating power. Some 985 colleges and universities have stamped their consent documents without much consideration. Some colleges suffered losses and were reluctant to publicize them.
Waiting until the subway proposal was a fact of life, other vibration damping measures had to be used. China Electronic Engineering Design Institute Co. Ltd. has given Fudan University, Nanjing University and many other colleges and universities affected by the subway have done vibration reduction programs.
Vibration Technology Research Center engineer Zuo Hanwen told reporters that the best program is a comprehensive vibration reduction, in addition to laying steel springs under the track floating plate, at the same time in the construction of the instrumentation building at the beginning of the installation of vibration isolation bracket supported by the spring. If the building has been completed, can only be installed under each instrument vibration damping table, the cost will be greatly enhanced.
After the opening of Line 16, BYU can only take the second program. Zhang Zhiqiang, director of the Office of Environmental Protection in the Department of Laboratory and Facilities Management at NU, estimated that a state-of-the-art air-spring vibration damping table would cost about one to two million yuan, and that NU would need to dampen the vibration of the instruments "in dozens of hundreds of such an order of magnitude".
Witness the advanced German floating plate, cumbersome building repair and relocation and expensive subway rerouting, NU's most sophisticated electron microscope in the future underneath the body will also be fitted with a complex vibration-damping table. But whether it can escape the subway's vibrating interference is anyone's guess.
Above from: Shangguan