Original from Zijing.com, the first release of Zijing.com, please add Zijing (ID: zijingkeji) to reprint. Cover picture: Panoramic view of the shield machine (Source: Tencent Technology) [Preface] The development of a country's economic construction and the advancement of the mod

　　　The original production of Zijing.com, the first release of zijing.com, please add zijing (ID: zijingkeji) to reprint.

Cover picture: Panoramic view of shield machine (Source: Tencent Technology)

　【Foreword】The development of a country's economic construction and the advancement of the modern industrial process are inseparable from the equipment manufacturing industry. It is a high expression of a country's manufacturing strength.

　　 Equipment manufacturing industry is a general term for various manufacturing industries that provide equipment for various economic departments to carry out simple production and expand reproduction. It is the core part of the industry and undertakes the important task of providing work machine to all departments of the national economy and driving the development of related industries. It can be said that it is the heart of industry and the lifeline of the national economy, and an important cornerstone supporting the country's comprehensive national strength.

　　Since the founding of New China, we have begun to speed up the deployment of equipment manufacturing industry. The Northeast region is the earliest equipment manufacturing base in my country.

　　Shield machine is an important tool and equipment for the construction of national infrastructure such as roads, railways, and airports. Shield machines occupy an important position in the equipment manufacturing industry. Since the "Eleventh Five-Year Plan" in my country, various transportation facilities have achieved remarkable achievements. Especially for the construction of high-speed rail, as of the end of 2020, the new operating mileage of railways nationwide exceeded 4,800 kilometers, further weaving the "eight vertical and eight horizontal" high-speed rail network.

　As of the end of 2020, my country's railway operating mileage reached 138,000 kilometers, ranking second in the world, of which the mileage of high-speed rail was 39,800 kilometers, ranking first in the world. This mileage of open to traffic is about 7.4 times that of Spain, the second place in the world.

　　The first domestic high-speed rail large-diameter shield machine was launched in Changsha on September 29, 2016 (Source: Xinhua News Agency)

　　　1. Understand the shield machine

　　　. Shield machine definition

　　　Shield machine (English name: shield machine) is an tunnel boring machine that uses the shield method. The construction method of the shield structure is to build (lay) the "shield" (referring to supporting pipe sheet) of the tunnel while excavating, which is different from the open construction method.

Internationally, generalized shield machines can also be used in rock formations, but they are different from open (non-shield method) tunnel boring machines. In my country, tunnel boring machines used in soft soil strata are conventionally called (narrow sense) shield machines, and those used in rock strata are called (narrow sense) TBM.

　　 shield mechanism is generally divided into hand-excavated shield structure, extruded shield structure, semi-mechanical shield structure (local air pressure, global air pressure), and mechanical shield structure (open-chest cutting shield structure, air pressure shield structure, mud and water pressurized shield structure, soil pressure balance shield structure , hybrid shield structure, special shield structure).

　　. Working principle

　　The basic working principle of a shield machine is to dig the soil with a steel component of a cylinder forward along the tunnel axis. The shell of the cylindrical assembly is a shield, which plays a temporary support role in excavated tunnel sections that have not yet been lining , withstand the pressure of the surrounding soil layer, and sometimes also withstand groundwater pressure and keep the groundwater outside. Excavation, soil discharge, lining and other operations are carried out under the cover of a shield.

　　. Effective features

　　According to the relevant literature of German Industry 4.0, the working efficiency of the shield machine is more than 10 times that of ordinary tunnel boring equipment, and the construction difficulty is greatly reduced and the safety is greatly improved. Although the shield machine is expensive, it can increase the subway excavation effect by 8 to 10 times. Moreover, during the construction process, there is no need to demolish large areas on the ground, no traffic is blocked, no noise in construction, no subsidence, and no impact on the normal life of residents. However, large shield machine technology has high added value and complex manufacturing process. Only a few companies in Europe, the United States and Japan can develop and produce it internationally.

　　The shield machine has been launched for nearly 200 years. It began in the UK and developed in Japan and Germany.Over the past 40 years, through the exploration and research of key technologies in soil pressure balanced and mud-water shield machines, such as effective sealing of shield machines, ensuring the stability of the excavation surface, controlling the surface uplift and collapse within the specified range, the service life of the tool, and the replacement of tool under sealing conditions, some harsh geological such as treatment technology for high water pressure conditions, the shield machines have developed rapidly. shield machine, especially soil pressure balanced and mud-water shield machine, has developed rapidly in Japan due to the rapid economic development and actual engineering needs. Germany's shield machine technology is also unique, especially during underground construction, where the sealing is guaranteed and the tool on the cutter plate is replaced under air pressure of up to 0.3MPa, thereby increasing the length of the shield machine's excavation. Germany also developed the replacement of worn tools from the normal pressure space inside the large diameter cutter plate under sealing conditions.

　　The selection principle of shield machine is to adapt to local conditions, improve the degree of mechanization as much as possible, and reduce the impact on the environment.

　　 2. Development history of shield machine

　　. Classification

　　　Shield machine, full name is a special engineering machinery for tunnel boring. modern shield boring machine integrates light, mechanical, electrical, liquid, sensing, and information technology. It has the functions of excavation and cutting soil, conveying soil ballast, assembling tunnel lining, measuring guide and correction. It involves many disciplines and technologies such as geology, civil engineering, machinery, mechanics, hydraulics, electrical, control, and measurement, and must be designed and manufactured in accordance with different geology, with extremely high reliability requirements. Shield tunnel boring machines have been widely used in tunnel projects such as subway, railway, highway, municipal, and hydropower.

　　⑴Semi-open

　　Hand-excavated and semi-mechanical shield structures are both semi-open excavated. This method is suitable for good geological conditions. The excavation surface can maintain stability during excavation or when auxiliary measures are provided. The excavation is generally excavated layer by layer from the top. If the soil layer is poor, you can also use a jack to support the excavation surface temporarily. Open excavation is used to deal with isolated obstacles, correct deviations, and over-excavation are easy to other methods. In order to minimize disturbances to the formation, the over-excavation amount and exposure time should be appropriately controlled.

　　⑵Mechanical cutting

　　Refers to the excavation method of a full-section rotary cutting cutter plate with a diameter similar to the shield structure. According to the quality of geological conditions, the large knife plate can be divided into two types: no sealing plates between the knife frames and sealing plates. The unsealed plate between the knife holder is suitable for conditions with good soil quality. The excavation method of large cutter plates is not as convenient as the open excavation for over-excavation when constructing curves or correcting deviations. In addition, clearing obstacles is not as good as opening excavation. The shield structure using a large knife plate has a complex mechanical structure and consumes a lot of power.

　　⑶Net format

　　Excavation is carried out in the grid format, and the excavation surface is divided into many grids by grid beams and grids. The support effect of the excavation surface is caused by the concentrating force of the soil and the resistance within the grid thickness range. As the shield advances, the soil is squeezed out of the grid. Adjust the opening area of the grid according to the nature of the soil. When excavating in the mesh format, after all jacks are retracted, a large shield retraction will occur, resulting in surface settlement. Therefore, effective measures must be taken during construction to prevent the shield from retraction.

　　　⑷Extruded

　　Full extrusion and partial extrusion excavation, since no or only partially unearthed, there will be a great disturbance to the formation. During the construction axis, try to avoid ground buildings. During local extrusion construction, the amount of unearth must be carefully controlled to reduce and control surface deformation. During full extrusion construction, the shield structure squeezes the soil within a certain range around it.

　　. History of the development of shield machine

　　The idea of shield machine method was born in the UK in the early 19th century and has a history of 200 years. Before the introduction of the shield construction method, tunnel construction mainly relied on excavation. However, in terms of urban tunnel construction, the excavation method is limited by terrain, landform and environmental conditions; the excavation method brings great inconvenience to urban traffic; the formation subsidence caused by excavation is large; the noise and vibration of construction machinery; and the pollution caused by construction to the environment, etc.

　　In the 18th century, no British proposed the idea of building a transThames tunnel underground in London, and discussed specific excavation methods and the use of machinery. By 1798, we began to work on achieving this idea, but the plan was frustrated because the shaft could not be dug at the predetermined depth. But the idea of the Cross-Thames Tunnel is growing day by day. Four years later, Torevix decided to build a tunnel connecting the two sides of the straits from another location, and the construction started again. Various difficulties were overcome during construction. When the excavation reached the last 30m, the tunnel was flooded with water on the excavation surface. The idea of crossing the Thames River was shattered again. It took five years for the project to be forced to terminate. The cross-Thames plan has not made significant progress in the next 10 years.

　In 1818, Brunel observed the process of small insects corroding the bottom of the wooden boat into holes, and thus gained inspiration. On this basis, he proposed the shield construction method and obtained a patent. This is the so-called prototype of the open hand-drawn shield. Brunel was very confident in his new approach and in 1823 he planned another road tunnel on both sides of the Thames in London. Subsequently, the plan was confirmed by the then Congress and the construction began in 1825. The tunnel is 458m long and the tunnel section is 11.4m×6.8m. The project was progressing smoothly, but the project was forced to be suspended due to the sinking of the strata. But Brunel was not discouraged and disappointed. He summed up the lessons of failure and made seven years of improvement to the shield structure. Later, the project started again in 1834. After seven years of careful construction, the tunnel was finally completed in 1841. Brunel uses a square cast iron frame shield in the tunnel. After 20 years of Brunel's challenge to the Thames Tunnel to the tunnel construction, Brunel has overcome all kinds of difficulties and finally won the final victory after unremitting efforts. At this time, he was already 72 years old. Brunel's contribution to the shield construction method is extremely outstanding, which is a consensus among later generations.

　　From Brunel's square shield, shield technology has undergone 23 years of improvement. By 1869, the second tunnel across the Thames was built, and for the first time, it used a circular section with an outer diameter of 2.18m and a length of 402m. This project was undertaken by Burlow and Great. Great uses a newly developed circular shield, using cast iron fan-shaped pipe pieces until the tunnel excavation is over. Great then succeeded in the construction of the South London Railway Tunnel in 1887, using the shield and air pressure combination method, which laid the foundation for the current shield and construction method. From the repeated failures and setbacks of Torevix at the beginning, to the introduction of Brunel's shield construction method, and then improving it into Great's shield construction method, after 80 years.

　　The longest railway tunnel in the world at that time designed by British engineer Isambard Kingdom Brunel, the Great Western Railway Line (Source: Baidu Encyclopedia)

　　The shield construction method was introduced to the United States, France, Germany, Japan, the Soviet Union and other countries from the end of the 19th century to the mid-20th century, and was developed to varying degrees. The United States first developed a closed shield structure in 1892; in the same year, Paris, France used concrete pipe sheets to build sewer tunnels; from 1896 to 1899, Germany used steel pipe sheets to build the Berlin tunnel; in 1913, Germany built the Elbe Tunnel with a horseshoe-shaped cross section; in 1917, Japan used shield structure construction method to build the National Railway Flying Line, but later stopped using it due to poor geological conditions; in 1931, the Soviet Union built the Moscow Metro with an English shield. The tunnel was constructed with chemical grouting and freezing. In 1939, Japan used hand-drawn circular shields to build a Guanmen tunnel with a diameter of 7m; in 1948, the Soviet Union built the Leningrad subway tunnel; in 1954, China built a φ2.6m circular shield hydrophobic tunnel; in 1957, Beijing, China built a φ2m and 2.6m shield sewer tunnel; in 1957, Japan used a closed shield to build a Tokyo subway tunnel. In short, although the shield construction method has also made progress in the past 50-60 years, the characteristic of this period is that the shield construction method has been promoted and popularized in countries around the world.

　　The shield construction method continued to develop and improve in the 1960s and 1980s, with remarkable achievements.In 1960, the United Kingdom began to use drum excavators; in the same year, New York, the United States was the first to use hydraulic jack shield; in 1964, the mud-water shield was the first to use mud-water shield in Japan; in 1969, Japan implemented mud-water pressurized shield construction for the first time in Tokyo; in 1972, Japan successfully developed soil-pressed shield structure; in 1975, Japan successfully launched soil-pressed shield structure; in 1978, Japan successfully developed high-concentration mud-water shield structure; in 1981, Japan successfully developed bubble shield structure; in 1982, Japan successfully developed ECL method; in 1988, Japan successfully developed mud-water double-circle overlapping shield structure method; in 1989, Japan successfully developed HV method and grouting shield structure method. In short, the characteristic of this period was the development of a variety of new shield construction methods, mainly mud-water and earth-pressure shield construction methods.

　　. Overview of the development of my country's shield machine

　　⑴The road to independence: From nothing to

　　"At present, there are no purely imported shield machine in the domestic market. Domestic shield machine, whether it is cost-effective or technical content, is not inferior to imported goods." Hao Luping, deputy director of the Party and Mass Work of China Railway Engineering Equipment Group Shield Manufacturing Co., Ltd., said in an interview with the media. But just ten years ago, China's shield machines were still heavily dependent on imports. According to Hao Luping, China's tunnel construction has mainly gone through four stages.

　　st stage : In the 1950s, the original method of manual excavation was mainly adopted, "steel brazing and sledgehammer, punching the hole and then firing the cannon" was mainly adopted;

　　st stage : In the 1970s, the principle of drilling and explosion method was used, and the degree of mechanization was improved, but it was mainly based on manpower;

　　st stage : In the 1980s, the principle of drilling and explosion method was still used, but the level of mechanization was higher, and rock drilling trolleys were used for drilling operations, and large-scale mechanization was carried out with lining templates;

　　st stage : In the 1990s, the shield machine was used to carry out operations, and the degree of mechanization was comprehensively improved.

　　In 1997, China introduced two shield machines from Germany for the first time to dig the Xikang Railway Qinling Tunnel . Back then, an imported shield machine sold for as much as 300 million yuan. Until 2008, China's shield machine relied heavily on imports. The foreign side has a monopoly on technology, and China is not allowed to participate during maintenance, and the working hours required for maintenance are also completely dependent on the foreign side, which seriously affects the progress of China's project.

　　 In order to get rid of the predicament, in August 2002, "China Railway Equipment" established a R&D team of 18 people. After six years of technological breakthroughs, China's first composite shield machine with independent intellectual property rights was successfully launched in 2008 and was first applied to the Tianjin Metro project, realizing the transformation from "using shields to building shields".

　　⑵The road to take off: From the best to the best

　　The ten years after the successful development of the first domestic shield machine is a decade of rapid development of China's shield machine industry. All of this can be seen from the development timetable of China Railway Equipment.

　　In December 2013, China Railway Equipment successfully developed a super-large cross-section rectangular shield, mainly used for the construction of urban underpass tunnels and underground parking lots;

　　In February 2016, China Railway Equipment successfully developed the world's smallest diameter 3.5-meter hard rock shield machine;

　　In October 2016, China Railway Equipment successfully began excavation and development of the "Menghua" shield machine specially customized for the Baicheng Tunnel of the Menghua Railway, marking that China is at the world's leading level in the field of special shields;

　　Next, China's largest diameter soil pressure balance shield machine, China's largest diameter hard rock shield machine, and China's largest diameter mud water balance shield machine were launched one after another, and China's independently developed shield machine has moved from an advantage. Hao Luping said that in recent years, the R&D team of China Railway Equipment has been developing and customizing according to different project needs, and the technology of shield machine is also constantly breaking through.

　　Made in China's shield machine is gradually gaining popularity among overseas customers. In January 2013, China Railway Equipment's No. 50 shield designed and manufactured by Malaysia was launched and applied to the Kuala Lumpur Metro project. In 2015, China Railway Equipment signed a procurement contract for 6 7.54-meter-diameter soil pressure balance shield machines at one time, and the equipment was used in the 11-kilometer-long Israeli tunnel project.In 2016, China Railway Equipment provided more than 10 shield machines to Singapore for its subway project construction.

　It is understood that after the "Chunfeng", China Railway Equipment's large-diameter shield machine orders have increased. China Railway Equipment has mastered the manufacturing technology of shield machines with a diameter of more than 15 meters, and the largest shield machine in the world is currently 17 meters. Hao Luping told reporters with confidence, "As long as customers have such demands, we will also produce 17-meter-diameter shield machines in the future."

　　　The domestically produced shield machine with a maximum diameter of 15.08 meters, which was launched in 2018, is the "Spring Breeze" (Source: CCTV.com)

　　　⑶Independent Innovation: Going to the World

　　 Currently, the domestic shield machine with independent intellectual property rights in China is the domestically produced "863" series shield machine developed by Shanghai Tunnel Engineering Co., Ltd. .

　　In July 2007, Geng Hongchen, chairman of North Heavy Industry Group, and the original shareholders of French NFM Company, officially signed an equity transfer agreement, successfully ending the two-year merger and acquisition negotiations with absolute control, allowing Northern Heavy Industry to have the world's most advanced full-series tunnel shield machine core technology and well-known brand.

　　On November 14, 2015, China's first domestic railway large-diameter shield machine developed by China Railway Construction Heavy Industry Group and China Railway 16th Bureau Group was launched in Changsha. It has completely independent intellectual property rights, breaking the technology monopoly abroad for nearly a century and will accelerate China's rapid urbanization and the construction of a large railway network. The large-diameter shield machine that was removed from the line was excavated in this line, with a total length of 100 meters. Each unit is more than 20 million yuan cheaper than the imported similar products. It has high cost performance and good reliability. It can be used in a variety of complex formations. After being removed from the line, it will serve the Guangzhou-Zhuhai intercity rail transit line.

　　On March 13, 2018, the export overseas super-large diameter shield machine independently developed by China was taken offline in the assembly workshop of China Jiaotong Tianhe Machinery Equipment Manufacturing Co., Ltd. This super-large diameter mud and water pressure balance shield machine with a diameter of 12.12 meters will be used in China's largest shield road tunnel project overseas - the Bangladesh Canapri River Tunnel Project. This is also the largest diameter shield machine put into use in South Asia, ending the monopoly of Europe and the United States.

　　On February 23, 2019, two earth pressure balance shield machines of China Railway Equipment Group successfully passed the on-site acceptance and were officially delivered to Japan's Nissom Construction Company. The two equipment will be used in the C882 project of Singapore Metro Ring Line 6. The "China Railway No. 647" and "China Railway No. 648" accepted this time are the first shield equipment provided by China Railway Equipment to Japanese customers. The cutter plates of the two shield machines have a diameter of 6.67 meters, a total length of the equipment is about 98 meters, and a total weight of about 632 tons. It has the ability to turn horizontally within a radius of 200 meters. It is a "small and strong" shield machine.

　As the highlight of Chinese equipment "going out", the entire process of these two shield machines from parts to assembly was also recorded by the camera. Almost as it was delivered to a Japanese company, the full-process video of the shield machine production process edited by Xinhuanet was also popular on YouTube and sparked heated discussions on the online forum in Singapore. Some Singaporean netizens even exclaimed like this, "Aren't we the developed countries? Why can't we build such machines?"

　　Surprised Singaporean netizens may not have imagined that the shield machine produced in China is not only of excellent quality, but also has the advantages of good stability and good adaptability to harsh geological conditions, but also has a huge sales volume. According to Xinhua News Agency, last year, the annual production capacity of shield equipment of China Railway Equipment alone reached more than 280 units, with a total of more than 780 shields shipped out of the factory, and has been exported to 18 countries and regions including Singapore, Lebanon, the United Arab Emirates, Italy, and , Qatar .

Today, domestic tunnel boring equipment has a share of more than 90% in the domestic market and accounts for more than two-thirds of the global market. Who would have thought that in such a big China more than ten years ago, there was no modern composite shield machine.

　　Shenzhen-5 shield machine (Source: Xinhuanet)

　　. From 0 to 1000

　　The importance of shield machine to underground tunnel construction is self-evident. In recent years, my country's shield machine has risen in all aspects. Shield machines usually determine the diameter of a cutter plate to distinguish the size. Usually, a shield machine with a diameter of more than 12 meters is called a "super-large shield machine". my country's shield machine ranged from 0 to 1,000 units, and it only took 12 years. from nothing to something, from less to more, how powerful is the domestic shield mechanism?

　　Along with the development of my country's "infrastructure maniac", the shield machine has developed rapidly. It integrates excavation, soil discharge, gravel, slag output, support, lining and sealing, and can realize the one-time forming of the main body of the tunnel. It has become an indispensable equipment for the construction of large tunnels such as subways, road cross-border tunnels, cross-sea tunnels, and water diversion burrows. It can better play the advantages of automation and intelligence, and is not affected by the weather.

　　Not only that, the speed of shield machine production and down-line in China is amazing:

　　 On September 27, 2020, China's super-large diameter shield machine "Jinghua" was launched in the Changsha First Industrial Park of China Railway Construction Heavy Industry Group. The maximum excavation diameter of this shield machine is 16.07 meters, the total length is 150 meters, and the total weight is 4,300 tons. It is the largest diameter shield machine developed in my country so far.

domestic 1000th shield machine was successfully launched (Source: Xinhuanet)

　On September 29, things that are milestones in the history of the development of domestic 1000th shield machine are worth remembering. The 1000th shield machine independently developed by China Railway Corporation, "Yuehai No. 14" was launched at Zhengzhou China Railway Engineering Equipment Group Co., Ltd. This is a soil pressure balance shield machine with a diameter of 8.64 meters, which will be used in the water resource allocation project in the Pearl River Delta in Guangdong.

　　 has ranged from 0 to 1,000 units, compatible with sizes, and has led the sales for three consecutive years! From the first composite earth-pressure balanced shield machine with independent intellectual property rights in 2008, to the fact that the shield machine orders are now more than 1,200, 1,000, and exported to 21 countries and regions, it has become a world-renowned leader in China's shield machine industry. It is innovation and creation that supports the rapid development of China Railway Equipment and the explosion of China's shield machine industry.

　　Looking back 14 years ago, the Chinese shield machine was still 0.

　In 1997, my country spent hundreds of millions of yuan to introduce two shield machines, which greatly saved labor costs and increased construction speed. However, from operating the machine to replacing the winch, including daily maintenance, there are no Chinese people, let alone technical research and development.

　　If there is a failure, these technicians from Western countries must be invited to repair it. Like other heavy imported equipment, Chinese people are never allowed to be present during repairs.

　　At the down-off ceremony, Zhuo Puzhou, Secretary of the Party Committee and Chairman of China Railway Equipment, said: "The shield mechanism is actually the 'competitive aura' of the Chinese people!"

　　Yes, 12 years ago, the key technologies of shield machines were monopolized by foreign countries, and shield machines used in China were heavily dependent on imports. If you do not master the core technology, the equipment needs foreign experts to travel across the ocean for maintenance. Expensive import costs, inefficient equipment maintenance, time-consuming cross-border communication, China is always subject to the application of shield machines, which seriously affects the efficiency and development of China's infrastructure.

　　 4. Medium-flow water

　　After years of exploration and hard work, my country's R&D team broke through the core technology blockade and developed and manufactured China's first composite soil pressure balance shield machine with independent intellectual property rights in 2008, China Railway No. 1, achieving a leap from 0 to 1. The following year, China Railway Equipment was established and established the largest shield structure research and development and manufacturing base in Zhengzhou, kicking off the industrialization of China's shield structure.

　　 At present, the domestic tunnel boring equipment market share can reach more than 90%, accounting for more than two-thirds of the market share in the global market.

　　The six main forces of domestic shield machines are: Railway Construction Heavy Industry, China Railway Equipment, China Communications Construction Tianhe, Shanghai Tunnel, Sansan Industry, and Northern Heavy Industry. These six companies have become the leading enterprises in China's six major shield machines.

　　It is really not easy for China to develop to its current state in just over ten years. As for why China has not directly produced a shield machine that can dig a 17-meter-diameter tunnel, relevant departments in our country have also explained it. It’s not that our technology cannot meet, but that there is no such demand at present. If someone really places such an order, I believe China can also build it.

　　"Build the Chinese's own shield structure, build the best shield structure in China, and build the best shield structure in the world." The three eye-catching words in the China Railway Equipment Shield Workshop are not only the most realistic portrayal of the China Railway Equipment Shield Machine's take-off road, but also a microcosm of China's history of industrial self-improvement.

　　On the same day that "Yuehai No. 14" was officially launched, on September 29, China's largest diameter mud water balance shield machine, the "Great Wall", was successfully launched in China Jiaotong Tianhe, Changshu, Jiangsu. The Great Wall is the 9th super-large diameter shield machine independently developed by China Jiaotong Tianhe.

　　In 2012, China Railway Equipment's first shield machine went abroad and was successfully applied to Malaysia. To date, China Railway Equipment has been used in Singapore, Italy, Poland, Australia, France and other places around the world. China Railway Equipment has the highest production and sales volume in the world for three consecutive years in 2017, 2018 and 2019.

　　In December 2013, China Railway Equipment successfully developed an ultra-large cross-section rectangular shield, and used the rectangular shield for the first time in the construction of urban underpass tunnels and underground parking lots; in October 2016, the world's first horseshoe-shaped shield, "Menghua", was customized for the Baicheng Tunnel of Haoji Railway. The application project won the 2018 ITA (World Tunnel Association) "Science and Technology Project Innovation Award", marking that China is at the world's leading level in the field of special-shaped shields; in 2018, the first domestic liaison channel shield machine was successfully applied in the Yinnan interval project of Ningbo Rail Transit Line 3.

　　Zhang Shuixun, deputy director of the Boring Machine Research and Design Institute of China Railway Construction Heavy Industry Group, said that the "Jinghua" shield machine uses a number of core technologies such as normal pressure tool change, telescopic main drive, efficient high-power mud-water circulation system, and high-precision gas-liquid independent balance control of the excavation surface; at the same time, it is also innovatively equipped with system devices such as pipe ring convergence measurement, pipe ring flatness detection, and synchronous dual-liquid grouting, which is more autonomous and intelligent, and is safer and more efficient. After it is released from the factory, it will be used in the construction of the East Sixth Ring Road renovation project in Beijing.

Shield machine body system being processed (Source: Tencent Technology)

　　5. Outlook

　　"There is a Shenzhou in the sky, a dragon in the sea, and a shield in the ground". The tunnel boring machine can cross mountains and seas. It is a high-end equipment integrating mechanical, electrical, hydraulic, sensing, information, mechanics, guidance research and other technologies.

　　 Currently, the largest shield machine in the world is a shield machine produced by the German Herric Group. Its shield diameter can reach a maximum of 17.6 meters, making it a "big master" among shield machines. The second largest is the "Besha" made in Japan, with a diameter of 17.5 meters, a length of 110 meters, and a weight of up to 7,000 tons. Although the newly launched Jinghua shield machine in my country is not the largest in the world, it has a small gap with it and is very advanced in technology. Yang Huayong, an academician of the Chinese Academy of Engineering, said in an interview with reporters: "The next step of China's shield structure will challenge the world record of 18 meters in diameter. A shield structure machine will be as high as 6 floors."

　　 China is the country with the largest scale, the largest number, the most complex geological conditions and structural forms, and the fastest development of construction technology in the world. A leader in Chinese tunnel boring machine enterprises represented by China Railway Equipment has emerged, and a series of landmark and innovative products such as China's largest diameter mud water balance shield machine, the world's first horseshoe-shaped shield machine, the world's largest diameter hard rock boring machine, and the world's largest diameter hard rock boring machine, and has continuously launched a charge to the world's largest, the world's smallest, and the world's first, breaking China's height in the field of world tunnel boring machines.

　　On December 14-15, 2019, China held the "High-end Forum on Underground Docking and Remanufacturing of Shields in the Sea". Professional media reported that the number of ships, quantity of shield machines, and shield tunnel construction mileage in each year have ranked first in the world.

　　Shield machine is a large machine with high technical content.The "New Progress in China's Shield Engineering Technology" first published on the forum disclosed that from the end of 2015 to the end of 2019, the number of shield machines in China has increased rapidly from about 1,000 (sets) to more than 3,000 (sets). These shield machines are distributed in urban construction sites across the country.

　　"In recent years, the development and technological progress of China's shield engineering industry have been amazing. The magnificent domestic super-large diameter shield machine is used in tunnel super projects such as the Yangtze River, the Yellow River and the sea areas." Wu Xuanpeng, chairman of the Beijing Shield Engineering Association, said that the number of ships, quantity of ships, and shield tunnel construction mileage in China have ranked first in the world. At present, the market share of various types of domestic shield machines in use nationwide has reached more than 90%, and has been exported to many countries.

　　6. Conclusion

　　China's equipment manufacturing industry has attracted attention from the world. Many fields have entered the world's first-class level, and a few industries are even ahead of the world. For example: in large-scale projects, shield machines dedicated to tunnel mining were used to rely entirely on imports, but now they are basically domesticized and have a very high level.

　Above we mentioned that on March 13, 2018, China launched a new tool and weapon after the "Caiyun" and specially manufactured for the highway and tunnel project in Bangladesh. Its diameter reaches 12.12 meters, a total length of 94 meters, and a total weight of 2,200 tons, which is much larger than the C13B frigate previously exported to the country. It is an ultra-large diameter mud and water pressure balance shield machine, and it is also a product we independently developed, and it is also the first ultra-large diameter shield machine exported.

　In the past, we could only import shield machines from abroad and could not introduce their technology. Western countries have always monopolized the international shield machines market, and they are not allowed to export related technologies to China. I didn’t expect that we would quickly break through related technical difficulties. Now, it is just meeting domestic demand, but what makes the West uneasy is that we have to sweep the overseas market again. This is similar to the previous situation. If others block us, then we will definitely break through and immediately turn it into a bargain price to compete with the West for the market. This is not an isolated case.

　　China's equipment manufacturing industry has made great progress in the past decade, and its distance from the advanced manufacturing powers of Europe and the United States is even shorter. It fully reflects the intelligence and innovation ability of the Chinese people, which is also the best proof that the Chinese nation stands on its own among the nations in the world.

　　The launch ceremony of the shield machine of the Kanapuri River Tunnel customized by China for Bangladesh (Source: Xinhuanet)

　　The world's first horseshoe-shaped shield machine, the world's largest diameter hard rock boring machine, China's largest diameter mud water balance shield machine, and China's first teaching and training shield machine were born in my country.

　　 It is reported that my country's shield machine with a diameter of 18 meters in cutting board is about to be manufactured and put off the production line, and this shield machine giant, which is quite 6 stories high, will also break the world record again.

Today, domestic shield machines have been widely used in many projects. High-speed rail and highway tunnels, water diversion tunnels, and even some national defense projects can use domestic shield machines. In the future, shield machines will also dig into unknown strata.

Video screenshot of netizens praising China's rail transit (Source: Sina Weibo)

　　The 40-year hard journey has been condensed into just 4 minutes. The super-burning counterattack of China's urban rail from "nothing" to "world's number one", made netizens burst into tears. These achievements are all attributed to the efforts of Chinese builders, but advanced shield machinery has also made great contributions.

　　The bell of the 2021 New Year has ringed, and we will face the dawn of the New Year and move towards a new goal! I wish the motherland prosperity and strength!

　　(The data in this article comes from Xinhuanet, Sina Technology, Tencent Technology, Wind Information, Industrial and Information Technology official website, etc.)

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　　(Source: Zijing.com Author: Century Ronin)