Tunnels and underground engineering are an important field of infrastructure construction. In recent years, relying on scientific and technological innovation, China's tunnel technology and equipment have achieved a leap from "following" to "leading", forming a complete industrial chain with global reach. On June 9, CCTV's "Xinwen Lianbo" broadcast a news report focusing on how scientific and technological innovation has helped China's tunnel technology and equipment lead the world.

The report stated that the world's longest undersea high-speed railway tunnel and the controlling project of the Ningbo-Zhoushan High-Speed Railway—the Jintang Undersea Tunnel—is currently being excavated from both directions. The two shield machines "Yongzhou" and "Dinghai", independently developed by China, will pass through high-water-pressure sections and various complex strata beneath the sea before achieving precise docking at about 78 meters below the sea surface.

Han Fengqi, technical director of the China Railway 14th Bureau Group's Ningbo-Zhoushan Railway project: The shield machine adopts a double-layer shell. After the undersea docking of the shields, the internal structure is dismantled and transported out, while the outer shell remains on the seabed to provide protection for the tunnel.

At present, China has become the country with

the largest number of tunnels and the largest construction scale in the world

From manual excavation to intelligent construction

China's tunnel construction has overcome many technical challenges

and multiple technologies rank among the world's forefront

As a leading enterprise in underwater shield tunneling and large-diameter shield tunneling

construction

China Railway 14th Bureau Group's large-diameter shield tunneling

uses scientific and technological innovation to promote the iterative renewal of intelligent construction techniques

leading tunnel construction

toward digitalization and intelligence at an accelerated pace

From May 10 to 14, China Railway Construction Corporation launched its underground space brand at the 2024 China Brand Day event, where underground space intelligent construction technology represented by China Railway 14th Bureau Group's large-diameter shield tunneling made a stunning appearance. China Railway 14th Bureau Group not only exhibited ten core technologies, but also presented the current brand innovation achievements of China's shield tunneling construction through a series of physical models.

And just last month, at the World Tunnel Congress exhibition, the China Railway 14th Bureau Group's large-diameter shield tunneling exhibition area displayed a large number of core shield tunneling technologies and ** achievements, including socket-type segments, synchronous dual-liquid grouting technology, cutterhead welding robots, and integral prefabricated box culverts, which were praised by experts, scholars, and enterprise representatives from France, Austria, and many other countries and regions.

In recent years, taking the high-quality development of large-diameter shield tunneling as the main line, China Railway 14th Bureau Group has pooled resources to carry out original and leading scientific and technological research, conducted technical research on efficient shield tunneling, green construction, and other areas, enhanced original innovation and integrated innovation capabilities, and boosted the building of a world-class large-diameter shield tunneling enterprise.

Restructuring the system and optimizing the innovation environment

Won 1 China Patent Excellence Award, achieving a zero breakthrough; authorized 70 patents during the year, up 43% from the previous year; received 3 Zhan Tianyou Awards, a record high; won 10 provincial and ministerial-level science and technology awards, with abundant results... In the just-concluded 2023, China Railway 14th Bureau Group comprehensively deepened scientific and technological innovation reform, and its innovation scorecard in the field of large-diameter shield tunneling construction was remarkable.

These achievements cannot be separated from the mechanisms and systems conducive to innovation built under the continuous optimization of the innovation environment. China Railway 14th Bureau Group continues to play the "first move" of innovation, cultivates and strengthens new quality productive forces, shapes new momentum and new advantages for development, and injects new impetus into the high-quality development of large-diameter shield tunneling.

At the Jinan Yellow River Jiluo Road North Extension Project, with the double-line breakthrough of the shield tunnel, the project is accelerating the organization of technical personnel to summarize the topic of "long-distance crossing of a large first-class water source protection area by a super-large-diameter slurry shield" and comprehensively planning the application of key technology patents.

During construction, faced with the long-distance crossing of a first-class water source protection area by a super-large-diameter shield, for which there was no precedent in China, the project technical team used means such as model tests, on-site monitoring, and numerical simulation to simulate the environment of key areas such as reservoir dams and water areas crossed by the shield machine, summarized the disturbance mechanisms and laws, achieved a maximum monthly advance of 332 meters, and set a tunneling record for long-distance crossing of a reservoir by a super-large-diameter shield.

At the beginning of this year, according to the patent management measures, China Railway 14th Bureau Group's Large-Diameter Shield Tunneling Company distributed 130,000 yuan in bonuses to the inventors of 49 patents, which further boosted the R&D enthusiasm of the project's technical personnel. At present, around this topic, they have already formed 8 invention patents.

The patent management measures are only one microcosm. Centering on the theme of high-quality development, they carried out high-tech empowerment actions, focused on the reconstruction of the scientific and technological innovation system, and successively revised and improved 6 management measures related to scientific and technological innovation, forming a full-process management system from science and technology project initiation and project R&D to achievement application, transformation and application, and property rights protection, providing institutional guarantees for scientific and technological innovation. According to statistics, they have won 1 National Technological Invention Award and 2 National Science and Technology Progress Awards, led or participated in the compilation of 11 national and local standards, and obtained 41 provincial and ministerial-level science and technology awards, 158 provincial and ministerial-level construction methods, and 380 invention patents.

Building platforms and stimulating innovation vitality

 Talent is the core driving force of scientific and technological innovation. China Railway 14th Bureau Group is committed to giving play to the innovative capabilities of technical leaders, and by building employee innovation studios and large-diameter shield tunneling craftsman studios, it creates a broad stage for innovation entities and fully stimulates the innovation vitality of the enterprise.

The shield tunnel of Section 2 of the Shanghai Airport Link Line undertaken by China Railway 14th Bureau Group is currently China's first large-diameter shield tunnel with small spacing and long-distance parallel operation of high-speed railways. The project adopted a fully prefabricated assembly structure system for the first time in China. All 2,470 curved components required for construction were processed and manufactured in the factory and then transported to the site for "building-block-style" assembly.

The prefabricated curved components were applied for the first time in a large-diameter shield tunnel, with a single block weighing up to 33.5 tons, high precision requirements for installation nodes, and great assembly difficulty. To improve the installation speed and precision of the components, they established a large-diameter shield tunneling craftsman studio, carried out research on the topic of "precision control of fully prefabricated assembly of internal structures", and developed a fine adjustment device with quality controllability and safety reliability as the starting point.

The fine adjustment device adopts a frame-type stepping structure. The whole machine integrates intelligent construction functions such as automatic detection and perception, automatic calculation and analysis processing, automatic decision-making and action execution, and human-machine interaction and information storage, and has 6-degree-of-freedom three-dimensional posture fine adjustment control. The device realizes automatic one-key assembly of curved components and controls the assembly precision within 1 millimeter.

According to statistics, focusing on directions such as synchronous dual-liquid grouting, small machinery, and long and large tunnels, the company has built 8 large-diameter shield tunneling craftsman studios. They advance side by side with 31 employee innovation studios, forming an innovation pattern that combines "professional leadership" with "broad employee participation".

At the construction site of the world's deepest undersea high-speed railway shield tunnel, the "Shenjiang No. 1" shield machine has advanced to 100 meters below sea level. The Pearl River Estuary Tunnel Project of the Shenzhen-Jiangmen Railway is located on the seabed of the Pearl River Estuary. It not only requires full-face hard rock tunneling of 2.75 kilometers, but also continuous crossing of 17 fault zones and branches with a section as long as 490 meters, making construction extremely difficult.

To this end, they focused on the research topic "Construction Technology for Long-Distance Crossing of Dense Fault Zone Strata with Super-Large Water Pressure by Large-Diameter Shields" and carried out technical research. Through research on mud film formation technology in fractured zones, in-tunnel grouting pre-reinforcement technology, tunneling control technology, and the application technology of clay-shield effect in fractured zone strata, they successfully completed the crossing of 15 fractured fault zones and are about to successfully reach the deepest point beneath the sea.

Focusing on application and driving industry innovation

Walking into the core section of the just-completed Nanjing Qiuteng-Wangjiang 220 kV line—the Lvboyuan shield section—in the formed tunnel, there is not a single hand hole or bolt on the segments. Looking from afar, the ring segments are neatly and consistently assembled with no visible misalignment, the tunnel facade has smooth curves and exquisite lines, and testing shows no leakage anywhere...

This benefits from the application of the new socket-type segment technology, which is also the first application in a domestic electric power shield tunnel. This technology effectively improves the stress resistance and deformation resistance of the tunnel structure and greatly reduces the pressure of later tunnel operation and maintenance.

It is reported that this technology was first successfully applied in the construction of the second channel of the Nanjing Jiangxinzhou sewage collection system, and it was also the first time a new socket-type segment was used in an underwater shield tunnel in China. Compared with traditional bolted segments, the new segment assembly saves half the labor. Direct positioning and insertion eliminate processes such as hand hole sealing and caulking, which not only improves the high-precision assembly skills of assemblers but also promotes the improvement of the intelligent assembly level of shield tunneling.

For many years, China Railway 14th Bureau Group has continuously strengthened technological innovation in improving tunnel safety and quality, pioneered and promoted a number of shield prefabricated construction techniques, and led the upgrading of intelligent construction.

Innovatively developed the key technology of synchronous dual-liquid grouting for super-large-diameter slurry shields, achieving remarkable results in the promotion and application of projects such as the Jiangyin-Jingjiang Yangtze River Tunnel and the Suzhou East Tunnel of the Nantong-Ningbo High-Speed Railway; the cutterhead welding robot has been successfully promoted in the Beijing-Binhai High-Speed Railway and the Suzhou East Tunnel of the Nantong-Ningbo High-Speed Railway; integral box culverts have been fully applied in the construction of projects such as the Pearl River Estuary Tunnel of the Shenzhen-Jiangmen Railway and the Tianxiang Avenue Tunnel of the Nanchang-Jiujiang High-Speed Railway.

Innovators are strong, and innovators win. With innovation as its "needlework" skill, China Railway 14th Bureau Group's large-diameter shield tunneling has tightly woven the underground transportation network, achieving full coverage of crossing rivers, lakes, seas, and cities, various complex geologies, application fields, shield diameters, and construction techniques. It has written a "report card" for the high-quality development of large-diameter shield tunneling and is also driving shield tunneling construction toward a new era of digitalization, intelligence, informatization, and unmanned operation.