Twin Tubes of Guangping Tunnel on Fujian Tian'an Expressway Fully Holed Through, Laying Solid Foundation for Full-Line Opening to Traffic

en.Wedoany.com Reported - On August 25, the Guangping Tunnel, a key controlling project on the entire Fujian Tian'an Expressway undertaken by China Railway 18th Bureau Group, achieved twin-tube breakthrough, opening up the critical passage for girder erection and pavement construction, and laying a solid foundation for the full line to be completed and opened to traffic on schedule.

The Tian'an Expressway is an important component of the fifth horizontal line of Fujian Province's "six vertical and ten horizontal" expressway network, and also the most convenient fast passage connecting Sanming and areas to its north with coastal cities such as Quanzhou and Xiamen, with the Sanming section spanning approximately 72 kilometers.

The section undertaken by China Railway 18th Bureau Group has a total route length of 25.06 kilometers, of which the Guangping Tunnel is a key controlling project on the entire line. It adopts a separated left-right twin-tube layout, with the left tube measuring 1,137 meters in total length and the right tube 1,138 meters. The tunnel traverses a zone of highly developed karst formations, where karst caves and karst grooves are widely developed, with fractured and weak surrounding rock accounting for as much as 65%. Multiple geological risks are superimposed, and adverse geological sections account for over 70% of the total tunnel length. Every drill-and-blast cycle and every round of excavation was fraught with challenges, making the tunnel a tough "hard nut to crack" constraining the full-line connection of the Tian'an Expressway.

The project team adhered to the construction principle of "advance support, strict grouting, short excavation, strong support, rapid closure, and frequent monitoring." In the fractured and weak surrounding rock sections, the single-cycle excavation advance was strictly controlled within 0.5 meters, rock bolts were densified, and double-layer steel arch support was adopted, combined with 24-hour uninterrupted dynamic monitoring, with blasting and support parameters fine-tuned in real time based on settlement and convergence data.

During the construction of the Guangping Tunnel, more than 20 karst caves and cavities of various sizes were revealed, most of which were silt and soft-soil filled karst caves and cavities, with the largest cavity reaching 15,700 cubic meters. The project team adhered to a "one cave, one strategy" approach, tailoring disposal plans for each case. For water inflow sections, multiple drainage holes were set up to divert groundwater in advance, and targeted measures such as backfilling, grouting, and spanning were adopted accordingly. Relying on this combined approach, the project team kept major risks such as water inflow and collapse away from the tunnel face, firmly held the safety bottom line, and ensured the smooth and orderly advancement of tunnel excavation.

In the face of a series of challenges, the project adhered to Party building leadership to consolidate the construction foundation, solidly carried out "two-entry" team activities, with "two-entry" personnel closely monitoring key processes such as tunnel face excavation, initial support, steel arch installation, and secondary lining, providing on-site command and problem-solving throughout. Meanwhile, regular team capacity-building and quality-improvement actions were carried out, with monthly organization of 4 job skill drills, 3 special hazard inspections, and routine on-site technical Q&A sessions, precisely targeting high-frequency risk points and technical difficulties in tunnel construction, providing hands-on guidance for team workers to standardize operations and refine skills. By strengthening frontline teams and solidifying on-site management, a solid foundation was laid for the safe and efficient breakthrough of the tunnel.

It is reported that upon completion, the Tian'an Expressway project will connect the Quannan Expressway and the Puyan Expressway, becoming a major longitudinal transportation artery linking Sanming, Quanzhou, and the Xiamen port city cluster, which is of great significance for improving the regional expressway network, strengthening transportation links between northwestern Fujian and southern Fujian, and promoting the economic and social development of areas along the route.