Engineering Through Rock and Faults: Geotechnical Challenges of the Daliangshan Highway Tunnel

In an ambitious endeavor, engineers in Sichuan Province, China, are breaking new ground—literally and figuratively—in highway tunnel construction. The Daliangshan No 1 Highway Tunnel project, a 15km-long twin-tube tunnel, is setting a precedent by using a central pilot tunnel to address geological challenges in advance. This groundbreaking method enhances safety, reduces risks, and offers insights for future highway tunnels in mountainous terrains.

The Daliangshan No 1 project faced daunting geological challenges, with poor rock conditions, high water ingress, and seismic faults. Traditional methods would have involved tunneling straight into these unpredictable conditions, putting the project at risk of delays, cost overruns, and safety hazards. Instead, the project team opted to construct a central pilot tunnel between the main tubes, a pioneering strategy for highway tunnels. This pilot tunnel allowed engineers to investigate geological conditions ahead of time and prepare for excavation, ultimately protecting both workers and equipment.

The central pilot tunnel provided several advantages beyond initial geological investigation. It allowed pre-excavation grouting and drainage, improved ventilation during drill-and-blast excavation of the main tubes, and helped manage vibrations in weaker rock areas. Additionally, the pilot tunnel served as an access route for transporting materials, making the overall excavation process more efficient. This method is well-known in railway tunneling, but its application in highway projects marks a significant shift in industry practices.

The pilot tunnel in Daliangshan not only supports construction but also plays a vital role in the tunnel’s long-term operations. Once complete, it will function as a drainage facility, an emergency refuge, and a ventilation duct for improved air circulation. This approach has proven so beneficial that future projects in Sichuan are already considering similar designs. The Daliangshan No 1 Highway Tunnel project showcases how innovative construction methods can pave the way for safer, more efficient infrastructure development in challenging terrains.