Dejiang Tunnel Project

Project Overview:

The Dejiang Extra-long Tunnel is a key control project on the Dejiang-to-Wuchuan Expressway—the “No. 1 Horizontal” route in Guizhou Province’s expressway network. It was originally the longest highway tunnel ever built and under construction in Guizhou Province. The left tube of the tunnel measures 5,505 meters in length, while the right tube is 5,425 meters long, with a maximum burial depth of approximately 537 meters. Construction began in August 2016. The tunnel passes through complex geological structures including the Wenxin Fault, the Changfeng Anticline, and the Shichao Syncline. Notably, the tunnel traverses a catchment area of the Shichao Syncline for a stretch of about 1,050 meters, covering a drainage basin of 29.6 square kilometers. Affected by the synclinal water-storage structure and the underlying mudstone barrier, a massive underground karst river system has formed above the tunnel, with water head pressures reaching as high as 210 meters and maximum inflow rates up to 600,000 cubic meters per day. The severe issue of high-pressure water bursts has earned the tunnel the nickname “Guizhou’s Most Difficult Highway Tunnel.” The project achieved breakthrough of the right tube in June 2020 and completed the entire tunnel safely and smoothly in October of the same year.

Project Highlights:

1. Successfully Tackled the World-Class Challenge of High-Pressure Water Inrush: Faced with extreme hydrological conditions—peak flow rate of 3.8 cubic meters per second and a maximum single-point water inflow approaching 15,000 cubic meters per hour—the project innovatively adopted a comprehensive management approach that prioritizes sealing, combines sealing with interception, and supplements it with pumping and drainage. In the course of implementation, advanced techniques such as the “membrane bag grouting for water stoppage” and the “rapid-setting paste grouting under high pressure” were flexibly applied. Moreover, when grouting-based water-stop measures proved ineffective, the team made scientifically informed and decisive decisions to directly proceed with excavation. As a result, they successfully traversed the high-pressure, water-rich zone, accumulating valuable experience for tunnel construction under similar geological conditions across China.

2. The pioneering drainage tunnel project breaks through the drainage bottleneck: To address the challenge that the originally designed central drainage ditch could not handle the massive daily inflow of 600,000 cubic meters, the project launched construction in 2019 of a dedicated drainage tunnel with a total length of 1,130 meters. This project features a cross-section consisting of a “semi-circular arch + straight sidewalls + bottom slab.” By simultaneously excavating at multiple working faces, the tunnel successfully passed through several large, filled-up karst cavities. It effectively gathers and diverts water from the nine major seepage points within the tunnel, fundamentally ensuring drainage safety during both the tunnel’s construction and operational phases, and demonstrating exceptional capabilities in emergency engineering design and construction under complex conditions.

3. Fine-grained supervision and science-based decision support: Faced with rare high-pressure water bursts and complex geological conditions, the supervision team engaged deeply and maintained full-process control. By strengthening advanced geological forecasting and analyzing monitoring data, the team provided critical technical support for construction decision-making. In particular, during the crucial phase of left-tunnel excavation, the supervisory team accurately assessed the limitations of grouting-based water-stopping methods and proposed—then actively promoted—a scientifically sound “direct excavation” approach. This not only saved substantial project costs but also bought precious time for the project to be completed on schedule, demonstrating the team’s high-level technical judgment and risk management capabilities.

4. Overcoming Adversity Through Exceptional Organizational Management: Faced with extreme challenges—including multiple sudden, large-scale water inflows that led to flooding and work stoppages, as well as a period when the export end came to a complete halt—every participating party in the project united their efforts and pooled their strengths. Through numerous expert reviews and optimized construction planning, and ultimately relying on tenacious efforts such as single-heading tunneling at the import end, the project team successfully achieved the safe breakthrough of this “most challenging tunnel” after four and a half years. This accomplishment underscores the project team’s extraordinary perseverance and outstanding engineering management capabilities.

Honored Achievements:

The project successfully addressed a world-class challenge in the construction of extra-long tunnels under rare domestic geological conditions characterized by high pressure, abundant groundwater, and karst formations. The comprehensive management technologies, emergency engineering designs (including drainage tunnels), and construction organization experience developed for this project have become landmark examples and invaluable assets in China’s highway tunnel construction sector when dealing with extreme hydrogeological conditions.
As a key project along the De’wu Expressway, the full completion of the entire route has laid a decisive foundation for achieving the goal of opening this section to traffic by the end of 2020. This project holds great significance for perfecting Guizhou Province’s expressway network and promoting the economic and social development of northeastern Guizhou. The successful implementation of this project has greatly boosted industry confidence and has been hailed as “another shining hallmark of Guizhou’s highway construction.”

Project Showcase: