On August 21, the Sutong Gil comprehensive pipe gallery project of Huainan Nanjing Shanghai 1000 kV AC UHV transmission and transformation project (hereinafter referred to as “Sutong Gil Comprehensive Pipe Gallery Project”) was officially opened.

Huainan Nanjing Shanghai 1000 kV AC UHV power transmission and transformation project is one of the 12 key transmission channels under the air pollution prevention action plan of the State Council and an important part of the UHV main grid in East China. After completion, the Huainan Nanjing Shanghai project will form an East China UHV AC loop network running through the load centers of Anhui, Jiangsu, Zhejiang and Shanghai, together with the Huainan Wannan Shanghai project of Anhui power transmission to the East, which will greatly improve the external power capacity of the East China Power Grid and improve the safe operation level of the power grid, It is of great significance to promote the sustainable economic and social development of East China and Jiangsu Province and further improve the level of power technology in China.

The project starts from the north bank (Nantong) access station and ends at the South Bank (Suzhou) access station. The tunnel is 5468.5m long and the shield diameter is 12.07m. It is one of the large-diameter and long-distance river crossing tunnels crossing the Yangtze River. The project investment is 4.763 billion yuan, which is planned to be completed and put into operation in 2019. It is invested and constructed by the State Grid and constructed by China Railway 14th bureau group.

The world's first UHV AC double loop power transmission and transformation project is connected through the Yangtze River comprehensive pipe gallery

The UHV communication between Huainan, Nanjing and Shanghai in East China realizes a double ring network and crosses the river by means of river crossing tunnel, which is known as an innovation in the history of power construction.

What is “Gil”?

Gas insulated metal enclosed transmission line (GIL) is laid in underground tunnel. Gil, i.e. gas insulated metal enclosed transmission line, adopts metal conductor rod for transmission, and encloses it in grounded metal shell for pressure gas insulation.

Compared with conventional cables, Gil has significant advantages such as large transmission capacity, low loss, high personal safety level, extremely low electromagnetic field, no environmental impact, high operation reliability, land saving and no electric (thermal) aging. It is especially suitable as a supplementary transmission technology under the condition of overhead transmission mode or limited cable transmission. Even from an economic point of view, Gil’s investment is lower than that of cable and its maintenance cost is lower than that of cable in large capacity and high voltage occasions.

The world's first UHV AC double loop power transmission and transformation project is connected through the Yangtze River comprehensive pipe gallery

The “Zhuoyue” shield machine started driving on June 28, 2017.

Why “crossing” rather than “crossing”?

Here, the Yangtze River is wide, and the narrowest place is close to 5000 meters. If the traditional scheme of building towers across the water is adopted, two towers will be built first in the water, and the height of each tower is designed to 450 meters. The foundation pit at the bottom of one tower is equivalent to 27 standard basketball courts, requiring more than 200000 cubic meters of reinforced concrete, limiting low altitude and affecting shipping; The tower foundation in the river has been washed by the river for a long time, and stones are used to fill the tower foundation every year, which will have an impact on Jiangsu port construction and infrastructure construction.

“More than 3000 large ships pass through the main channel of the Yangtze River every day. The technical and economic advantages of the overhead crossing scheme are not obvious and the construction risk is high.” Jiangsu electric power company has made full research on this.

The tunnel has the advantages of little impact on the surrounding environment and low operation and maintenance cost. The expert group headed by Qian Qihu, academician of the Chinese Academy of engineering, fully demonstrated that considering the geographical conditions and long-term economic development of Jiangsu, the State Grid Corporation of China decided to cross the river by tunnel.

The world's first UHV AC double loop power transmission and transformation project is connected through the Yangtze River comprehensive pipe gallery

Schematic diagram of tunnel section.

What does it take to cross the Yangtze River?

Shield machine is the most commonly used “artifact” for tunneling in the 21st century. Compared with manual tunneling, it has the characteristics of safety, environmental protection, high speed and high efficiency. In recent years, it has been widely used in the construction of river crossing tunnel. The shield machine passes through a long tunnel through processes such as automatic segment support and mechanical assembly. Therefore, the shield machine is vividly compared to “pangolin” and “steel earthworm”. A shield machine, worth hundreds of millions of yuan, integrates automation and intelligence, covering geology, civil engineering, machinery, mechanics, hydraulics, electricity, control, measurement and other disciplines and technologies.

The “Zhuoyue” shield machine used in the project is a shield machine “tailored” according to the actual situation of the project on the basis of the good cooperative relationship between China Railway 14th bureau group and Herrick, Germany in the field of large-diameter shield for more than ten years and the mutual support of core technologies.

The biggest challenges facing the project are high water pressure and complex and changeable geological conditions at the bottom of the river. The geological conditions in the river are complex, with the characteristics of high permeability, high compactness and high quartz content. The tunnel will pass through the Yangtze River levee, long-distance biogas stratum and the gully section in the river, which is technically difficult and high construction risk.

The world's first UHV AC double loop power transmission and transformation project is connected through the Yangtze River comprehensive pipe gallery

The “excellence” shield machine jointly developed has set a new world record in terms of production, manufacturing and on-site organization and commissioning cycle.

The excavation diameter of the shield machine is 12.07m, the total length of the equipment is 140m, and five frames are equipped behind it. During the excavation process, 22 pairs of hydraulic cylinders provide thrust up to 156000 kn, so that the cutterhead cuts into the tunnel face and drives forward. For the unavoidable biogas layer in the shield construction stratum of the project, based on the Swiss Suva mining safety code, the shield machine is specially equipped with special equipment to actively deal with harmful gases, so as to realize the functions of biogas detection, early warning and explosion-proof.

The cutter adopts the multi-level cutter design of advance cutter + scraper. 212 shell advance cutters and scrapers embedded with tungsten molybdenum alloy are used for face cutting to ensure the excavation efficiency. The cutter head is designed with 5 pairs of cutter arms to increase the opening rate to 36%. 2734 ring segments are installed in the whole tunnel, and the total amount of muck excavated and removed is about 625000 m3. In the central control room, all important data and real-time excavation parameters are visually displayed on the monitor. The operator monitors the basic automatic operation process and intervenes and adjusts it if necessary.

The world's first UHV AC double loop power transmission and transformation project is connected through the Yangtze River comprehensive pipe gallery

Internal layout of comprehensive pipe gallery.

How many “first” projects have created in the world and in China?

Sutong Gil integrated pipe gallery Yangtze River tunnel project is an ultra long-distance Gil innovative project with the highest voltage level, the largest transmission capacity and the most advanced technical level in the world. It is the first time in the world to apply large-diameter shield tunnel to power pipe gallery project.

Chen Peng, the project leader of China Railway 14th Bureau, said: “the lowest elevation of the tunnel is -74.83m, and the maximum water and soil pressure reaches 9.8ba. It is the electric river crossing tunnel with the deepest burial depth and the highest water pressure in China.” The water and soil pressure reaches 9.8 bar, which is equivalent to an adult elephant standing on a single seat of an ordinary car. It is a new world-class challenge to the safety of shield machine and construction personnel. “The Nanjing Yangtze River tunnel we built before has a water depth of 63 meters. This tunnel has set a new record.” Chen Peng said.

The tunnel passes through highly abrasive quartz sand and strong permeability stratum, which is the longest single head tunnel in China. The exploration data show that the tunnel has to pass through 1780m stratum rich in harmful gas.

River bottom excavation is also the power integrated pipe gallery with the highest risk in the construction of large-diameter river crossing tunnel.

In order to overcome world-class problems, under the guidance of the expert group headed by Qian Qihu, academician of the Chinese Academy of engineering, the shield machine suitable for geological, pressure bearing and harmful gas strata was jointly developed, and the explosion-proof design and transformation of the shield machine, lighting and exhaust system were carried out.

Since June 28, 2017, the shield machine began to excavate and penetrate. It took 14 months. The average daily excavation was 14.12m and the average monthly excavation was 417m, setting a new record for the construction of large-diameter shield tunnel in the world (the highest historical average rate of similar projects in China was 11.6m per day and 348m per month). The whole tunnel has no leakage point. Academician Qian Qihu praised the tunnel as an industry benchmark project with the best on-site management, the best physical quality and the fastest construction progress in China.

The world's first UHV AC double loop power transmission and transformation project is connected through the Yangtze River comprehensive pipe gallery

Tunnel construction scene.

The indissoluble bond between the large shield and Nanjing

Nanjing is destined to be the blessed land of the big shield company. As the pioneering work of a large shield company, Nanjing Yangtze River Tunnel represents the masterpiece of underwater tunnels in China today. With the first mover advantage accumulated in Nanjing Yangtze River tunnel, the large shield company has successively participated in the construction of a large number of large-diameter shield tunnel projects, such as Nanjing Metro Line 10 river crossing tunnel, Yangzhou Slender West Lake Tunnel, Wuhan Metro Line 8 Yangtze River tunnel, Beijing Shenyang high speed railway Wangjing tunnel, Wuhu Yangtze River crossing tunnel, etc. at the same time, it has also won the bid for the first phase of Nanjing Metro North-South Line, Nanjing Ningli, Ninghe Nanjing Metro Line 7 and other metro projects. In August 2016, the Party committee of the 14th Bureau Group established the first large shield engineering company in China in Nanjing in accordance with the principle of “specialty + focus” based on the strategic needs of strengthening, expanding and specialized shield plate.

At present, 5 cross river tunnels are under construction in the Yangtze River, and 4 have been undertaken by the large shield company of China Railway 14th Bureau. As a local enterprise in Nanjing, the Nanjing Yangtze River tunnel, the river crossing tunnel of Nanjing Metro Line 10 and the river crossing tunnel of Wuhan Metro Line 8 undertaken by the large shield company have been opened to traffic. Sutong Gil comprehensive pipe gallery project has achieved tunnel connection and Nanjing Wuqiao Jiajiang tunnel is progressing smoothly.

The Nanjing Yangtze River tunnel project, known as the “masterpiece” and the “first tunnel of the Yangtze River”, represents the highest standard of underwater shield tunnel construction in China. The two achievements won the “second prize of national scientific and Technological Progress Award”, the “Luban Award”, “Zhan Tianyou Award” and the “national excellent Gold Award”.

The river crossing tunnel of Nanjing Metro Line 10 adopts the world’s first “small space atmospheric pressure tool changing technology” and won the “National Technological Invention Award”.

Wuhan Metro Line 8 river crossing tunnel is the world’s largest single tube double track Metro river crossing tunnel. It has overcome the technical problems such as gear hobbing tool exchange under atmospheric pressure and created a world record of 688 meters per month driven by large-diameter slurry balance shield machine.

The UHV communication between Huainan, Nanjing and Shanghai in East China realizes a double ring network and crosses the river by means of river crossing tunnel, which is known as an innovation in the history of power construction.

Sutong Gil integrated pipe gallery project is an ultra long-distance Gil innovation project with the highest voltage level, the largest transmission capacity and the most advanced technical level in the world.

Nanjing Wuqiao Jiajiang tunnel is the largest diameter shield tunnel under construction across the Yangtze River.

In the field of super large diameter and underwater shield construction, the major shield company of China Railway 14th bureau took the lead in realizing five “full coverage” in China: full coverage of crossing “rivers, lakes and sea cities”, full coverage of geological conditions, full coverage of involved industries, full coverage of shield diameter and full coverage of construction technology. Innovate and apply special processes such as back dragging in the large-diameter shield tunnel, initial receiving in the tunnel, drilling and blasting + shield air pushing, exploration and treatment of karst caves in the river, offshore drilling and blasting treatment of boulders and bedrock protrusions, river surface and sea surface grouting consolidation, atmospheric pressure knife changing, pressurized warehousing, rotary water knife mud cake cutting, mud flocculation green treatment, Hengdun mud warehousing, etc, More than 150 invention patents and innovative construction methods have been formed.

For the segmented business in the large shield industry chain, “five in one” escorts the large shield construction, and adheres to the design mode of “drawing design + Construction Group Design”; “Manufacturer R & D + independent R & D” R & D mode; “Factory manufacturing + professional supervision” shield machine procurement mode; “Site control + remote monitoring” construction supervision mode; “Technology center + expert team” technology breakthrough mode.

The large shield company has established the development concept of “strengthening the enterprise through science and technology and revitalizing the enterprise through innovation”, took the lead in developing the digital monitoring system for large shield construction, established the shield data monitoring command center of the 14th Bureau, and realized the online monitoring of shield construction projects across the country. Qian Qihu, Liang Wenhao, Shi Yuxin and other experts and academicians were employed to form an expert group for remote guidance to “feel the pulse of experts” on engineering difficulties, quickly eliminate Engineering “dangerous situations”, timely rectify potential safety hazards, and make full use of advanced means such as big data analysis and intelligent early warning control to analyze shield posture early warning, daily driving analysis, tool change Significant results have been achieved in mud circulation monitoring and safety risk monitoring, which has greatly enhanced the management and control ability of the construction site and improved the safety of construction operations in key links.

In addition, the large shield company also cooperates with Southwest Jiaotong University, Beijing University of technology, Tongji University and other universities and authoritative scientific research institutions to establish a shield technology R & D center. The two sides have carried out in-depth cooperation in intelligent identification of safe operation, shield tunneling early warning, digitization of geological stratum information, structural safety assessment early warning and fine control of construction slag and soil, so as to improve the shield construction technology to the direction of “intelligent” and “semi intelligent”.

The large shield company of China Railway 14th Bureau Group focuses on the corporate vision of “leading global construction and development and creating a miracle of human dream”, and focuses on the goal of “crossing rivers, lakes and sea cities and becoming a leader in shield industry”, so as to contribute to the construction of “strong, rich, beautiful and high” new Jiangsu.

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