Geological Investigation for the Dejiang Tunnel on the Dejiang to Wuchuan Section of the Dejiang to Xishui Expressway in Guizhou Province

Project Overview:

The Dejiang to Wuchuan section of the Guizhou Province Dejiang to Xishui Expressway is the “First Horizontal” route in the “678 Network” of the Guizhou Province Expressway Network Plan. It starts at Qianjia Interchange northwest of Dejiang County, where it connects with the “Second Vertical” Yanhe to Dejiang Expressway, and ends at Yujiawan southwest of Wuchuan County, where it joins the completed Wuchuan to Zhen’an Expressway. The total length of this section is 40.694 kilometers, with a total investment of 5.756 billion yuan. The entire route is designed to meet the standards of a fully controlled-access, four-lane dual-carriageway expressway, with a design speed of 80 km/h and a subgrade width of 24.5 meters. Bridges and culverts generally have the same width as the subgrade, and the design load is Class I highway. The Dejiang Tunnel, located between kilometer points K6+695 and K12+270, is the most critical control project along the entire route. With a total length of 5,505 meters, it is a separated single-slope tunnel, featuring a maximum burial depth of 581.67 meters.

The highway project is operating smoothly overall, and the geotechnical investigation has been successfully completed. By selecting an optimal route, this project effectively avoided major geological hazard zones and reduced the tunnel length by 31%, thereby saving approximately 660 million yuan in investment. The travel time at both ends of the tunnels has been significantly shortened—from one hour to 40 minutes—a reduction of 90% in transit time. This has enhanced the comprehensive transportation capacity of the Tujia ethnic region in northern Guizhou, greatly boosting the development of tourism. Moreover, it has accelerated the exploration and utilization of local resources, helping to achieve poverty alleviation goals and creating favorable conditions for poverty alleviation and development in the contiguous, concentrated areas of extreme poverty in northern Guizhou. By breaking through the development bottlenecks in deeply impoverished minority regions, the project has provided strong support for local poverty alleviation efforts, increasing per capita disposable income by 48.8% and effectively promoting the local economic development level. The results of the investigation have yielded significant economic, social, and environmental benefits. They represent an advanced standard within the industry and serve as an excellent reference for future engineering investigations conducted in similar geological environments.

Project Highlights:

Through hydrogeological surveys and evaluations of the special-purpose, ridge-crossing karst tunnel, we conducted a thorough study of regional hydrogeological data. Relying on geological exploration data and carrying out tracer tests on-site, we identified the underground boundary and flow velocity of the Nao Shui rock formation, thereby resolving the tunnel site-selection issue. By avoiding the areas with abundant groundwater, we were able to shorten the tunnel by 955 meters and significantly reduce the overall construction costs.
A reliable hazard assessment system for karst tunnel water inrush and flooding has been established, enabling accurate prediction and forecasting of water inflow volumes and significantly reducing the risk of tunnel water inrush and flooding.
By mastering the dynamic changes in the surrounding rock, we have accurately assessed and judged the stability of the surrounding rock and the safety status of the lining structure, providing a basis for the tunnel’s dynamic design and information-based construction.
Provide reference for the formulation and revision of standards such as the "Code for Geological Exploration of Highway Engineering," the "Regulations for Geological Exploration of Highway Engineering in Karst Regions," the "Regulations for Hydrogeological Exploration of Highway Cross-Mountain Tunnels," and the "Technical Regulations for Grouting and Sealing of High-Pressure Karst Water Inflows in Tunnels," thereby promoting technological advancement.

Honored Achievements:

First Prize for Excellent Highway Survey and Design in China’s Highway Transportation;
First Prize for Technological Innovation in Civil and Architectural Engineering, Guizhou Province;
Published 4 papers and trained 10 technical backbones and 4 graduate students.

Project Showcase: