Taotziya Tunnel

Project Overview:

The Taoziyaya Tunnel is a key control project on the Zhen'an to Xishui section of the Dejiang-Xishui Expressway in Guizhou Province. It is also the longest tunnel along the entire route, with a total equivalent length of 5,082 meters and a maximum burial depth of approximately 978 meters. The project’s estimated total investment was about 676 million yuan, and it was completed and opened to traffic in July 2021. The Taoziyaya Tunnel is an exceptionally rare long highway tunnel in China that integrates various adverse geological conditions. It is also the deepest highway tunnel in Guizhou Province and has been dubbed the “Geological Museum of Tunnels.” Adhering to the concept of green and high-quality engineering, the project actively applied scientific and technological breakthroughs, successfully overcoming a series of critical technical challenges—including the risk of coal burst triggered by the combined effects of high ground stress and extremely thick coal seams, precise gas control, and the management of large deformations in soft rock under high ground stress. The Taoziyaya Tunnel has filled several gaps in design codes and technical standards for complex geological gas tunnels, providing systematic and valuable experience that can be referenced for the design and construction of gas tunnels.

Project Highlights:

For the high-stress sections of extra-long tunnels at great burial depths, we innovatively proposed a dynamic identification principle—“macroscopic prediction in the early stage + precise verification during construction + comprehensive final assessment”—which enables the rational identification and correction of the high-stress state of tunnel surrounding rock. This approach guided dynamic design optimization for a total of 1,880 meters of high-stress sections, significantly reducing project costs by approximately 124 million yuan.
An innovative combined support system—incorporating “long and short rock bolts, a double-layer telescopic arch support, and an approximately circular cross-section”—has been adopted to effectively control large deformations in highly stressed, weak surrounding rock, thereby ensuring the structural integrity and operational safety of the tunnel and successfully addressing the challenging issue of supporting large deformations in extremely soft coal seams under high ground stress.
Addressing the challenging issue of gas drainage in ultra-high-voltage, low-permeability, extremely thick coal seams, we have innovatively applied hydraulic fracturing technology to enhance coal seam permeability. Combined with a segmented and zoned gas drainage design, this approach has significantly improved gas extraction efficiency—doubling the extraction rate and shortening the project duration by approximately three months.
A workflow for preventing coal burst in ultra-high-voltage, extra-thick coal seam groups has been proposed. This workflow integrates and applies a comprehensive technology that combines “advanced large-diameter canopy support + small-diameter grouting curtain + pre-embedded gas drainage channels within cable trenches” for both burst prevention and gas control, thereby ensuring safety during the construction and operation of high-gas tunnels and filling a technological gap in the highway industry in this regard.

Honored Achievements:

The “Second Batch of Green Construction Demonstration Projects in Guizhou Province’s Construction Industry” for 2020;
2021 NCE Tunnel Engineering Award (for the exceptionally long tunnel group of the Zhengxi Expressway, exemplified by the Taoziyaya Tunnel);
Second Prize for Outstanding Highway Transportation Design, 2022;
First Prize of the 2023 Guizhou Province Civil and Architectural Engineering Technology Innovation Award;
First Prize, 2024 Guizhou Province Outstanding Engineering Survey and Design Award.

Project Showcase: