On September 26, 2024, the major water diversion tunnel project (XE Water Diversion VIII) constructed by China Railway 16th Bureau achieved full-line breakthrough. This milestone marks the successful completion of a single-machine advance of 26.521 kilometers by the “Fenjin” TBM after more than six arduous years of operation, setting a new world record.
Project Overview
The water diversion tunnel spans a total length of 34.751 kilometers and is constructed in segments—three non-contiguous TBM-driven sections combined with four non-contiguous drill-and-blast sections. On July 4, 2018, the “Fenjin” TBM completed its assembly and commissioning preparations, officially commencing the first tunneling segment. Despite facing challenges such as ultra-long tunneling distances, frequent machine transfers, extended advance steps, high-difficulty construction, and stringent equipment maintenance requirements, the project team piloted the 175-meter-long “steel dragon” with remarkable speed, turning a marathon-length challenge into a series of sprints.(Learn more about TBM steel structures at Glory Rail !)
Geological and Technical Challenges
The TBM-driven segments account for a total length of 26.521 kilometers, while the manually excavated sections extend for 8.23 kilometers. The surrounding rock is primarily composed of gneiss and granite, with class II and III rock types representing 75.4% of the tunnel and over 86.8% classified as severely fragmented. In certain sections, the compressive strength of the rock reaches 180 MPa, forcing the TBM to engage in “hard-on-hard” confrontations with the robust rock mass. The extended tunnel length, heavy workload, complex operational tasks, frequent machine transfers, and high safety risks all imposed stringent demands on project management and equipment configuration.
In October 2019, the TBM encountered a sudden jam in a fracture zone. Analysis of the rock samples revealed that the TBM had met a fault zone composed of a mixture of angular conglomerate, fragmented rock, and interspersed fault clay. The extremely loose structure of this composite material posed a fatal risk for a TBM designed to “feed on hard rock and avoid soft rock.”
Innovative Solutions and Methodologies
In response to these challenges, the project team conducted extensive research on similar projects, organized design reviews, and performed detailed on-site investigations. They deployed a comprehensive surface detection plan and initially formulated a “reinforcement–cleaning–grouting–reinforcement” strategy. Leveraging the expertise at the company’s Academicians’ Expert Workstation and collaborating with external specialists and all construction stakeholders, the team implemented an integrated approach—including chemical grouting, dual-pipe canopy pre-support, and concrete backfill replacement—to reinforce the surrounding rock and prevent the fragmented material from exerting detrimental pressure on the cutterhead.
Building on enhanced pre-support measures, the “Fenjin” TBM overcame the adverse geological conditions. Starting from an initial advance of just 30 centimeters per cycle, the TBM gradually increased its step length to 70 centimeters, then 1 meter, 3 meters, and eventually 5 meters. Over the course of five months, the team successfully negotiated a fractured fault zone extending over 200 meters. Their innovative “TBM Escaping Method for Weathered and Altered Zones” was later recognized with the Advanced Construction Method Award by China Railway Construction, providing a critical reference for future projects.
Subsequent Achievements
During the third TBM segment, the team capitalized on the invaluable experience gained from the earlier stages. They successfully tunneled through high-hardness rock with a compressive strength of 180 MPa and overcame the frequent challenges posed by fractured fault zones. This phase achieved an average monthly advance of 446 meters, with the highest monthly progress reaching 771 meters.
Simultaneously, the project team embraced new technologies and methods, continually optimizing the concrete mix design and revising labor practices by introducing performance incentives. These improvements significantly enhanced the TBM’s operational efficiency. Notably, the time required to replace the “shoe” concrete—the most time-consuming process—was reduced from an average of 12 hours to just 4 hours, ultimately establishing a record daily advance of 40.8 meters.
Conclusion
The full-line breakthrough of the XE Water Diversion VIII project not only demonstrates the technical prowess but also sets a new benchmark in TBM tunneling performance. By innovatively addressing formidable geological challenges and optimizing construction methodologies, the project team has provided a landmark example of engineering excellence and operational efficiency in the realm of large-scale water diversion tunnel projects.
The perfect completion of a TBM tunnel project is dependent on the work carried out in the early stages of the project as well as the cooperation of all the construction stages. Glory Rail has a wealth of experience in tunneling projects and offers TBM-related steel structures and steel rails that are customized to meet the needs of the project.