Pengshui Tunnel of the Chongqing-Hunan Double-Track Expressway Under Construction

On August 20, the cumulative excavation of both tubes of the Pengshui Tunnel on the Chongqing-Hunan Double-Track Expressway—the longest tunnel under construction on a highway in Chongqing—surpassed the 20,000-meter mark, marking major progress in the construction of the expressway and laying a solid foundation for its full opening to traffic.

The Pengshui Tunnel has a left tube 11,135 meters long and a right tube 11,094 meters long. It is a double-tube extra-long low-gas highway tunnel and a controlling project of the entire line. Located in the Wuling Mountain area, the tunnel features complex terrain and geological conditions, with numerous ravines and steep cliffs and well-developed adverse geological phenomena. It passes through 9,100 meters of soluble rock, accounting for 82% of the tunnel's total length; groundwater is abundant, and there is a risk of encountering large-scale water and mud inrushes.

According to reports, owing to terrain constraints, large equipment had difficulty entering and exiting during excavation at the tunnel's exit end. The project team adopted a plan of building construction access roads along the cliff face; workers suspended on cliffs of nearly 90 degrees first removed dangerous rocks and then built the access road. An access road less than 1 kilometer long took 3 months to complete.

Facing complex geology and gas, the project team incorporated geological forecasting into process management, combining long-, medium-, and short-range forecasting methods with advanced geological drilling to ascertain the geology ahead. In parallel, automatic gas monitoring and worker monitoring were implemented, and safety management was carried out strictly as a gas tunnel—with strong ventilation, frequent testing, and advanced probing—to ensure safety. Since construction began on the Pengshui Tunnel, the project team has successfully passed through 14 karst caves and 2 adverse contact zones.

The Chongqing-Hunan Double-Track Expressway has a total length of 280 kilometers and consists of three sections: Banan to Pengshui, Pengshui to Youyang, and Wulong to Daozhen, with an average bridge-tunnel ratio of 80%. At present, construction of the three sections is progressing smoothly; 137 bridges have been erected and 60 tunnels have been holed through, and works such as pavement, electromechanical systems, traffic safety facilities, and buildings are also proceeding in an orderly manner. The Banan-Wulong and Pengshui-Youyang sections are expected to be completed and opened to traffic within the year, and the Wulong-Pengshui and Wulong-Daozhen sections are expected to be completed and opened to traffic next year.