Crossing the Jin'an River and piercing through Jinji Mountain, Fuzhou's first underground road has achieved a double-tube breakthrough ahead of schedule. It will be completed and open to traffic before the Spring Festival, playing a key role in connecting the Second and Third Ring Roads and enabling a rapid connection between Hudong Road and the Sanba Intersection of the East Second Ring Road.

The Hudong East Road project has a total length of about 1.9 kilometers, with the 1.6-kilometer tunnel section being the main focus of the efforts. The final 99-meter structural section of the tunnel was the toughest challenge.

“On October 24 last year, work began on the 99-meter structural section, and we had to complete the double-tube breakthrough before New Year's Day this year, which meant accomplishing four months' worth of work in two months,” said Lin Chengsheng, project manager of the Hudong East Road project for the owner, the Municipal Urban and Rural Construction General Company. Everyone was on edge: the tunnel was full of block stones, making excavation difficult, and time was extremely tight. In addition, the section is close to residential areas and is an open-cut section, so flying rocks from blasting would affect the surroundings.

What to do when blasting is not allowed? Use hydraulic breakers to excavate, mechanically breaking and chiseling away the stones one by one. How to speed up progress? Adopt an “unconventional” configuration with eight hydraulic breakers working simultaneously. Can efficiency be improved further? Expand to three work faces for streamlined operations, ensuring seamless connection between each process.

Finally, the “critical battle” was won on the 24th of last month, achieving the early breakthrough of the 1.6-kilometer tunnel.

The Hudong East Road not only crosses the Jin'an River and Jinji Mountain but also passes beneath office buildings and residential houses, with extremely shallow cover. In particular, the 180-meter section under the Tian Shui Yuan residential area consists of muddy soil with very high water content. Tunneling through this shallow “tofu” was no easy task.

“This is the most difficult tunnel I have encountered in my tunnel construction career!” said Ren Guoqiang, project manager of the construction contractor CCCC Tunnel Engineering Company. As a key project in Fuzhou, a temporary Party branch was established on the front line, consisting of 15 members from the construction administrative department and the five responsible entities: construction, survey, design, construction, and supervision. In addition to reinforcing the retaining walls of residential houses, they also successfully solved the problem of tunneling through the muddy section.

“There is no precedent in Fuzhou's previous tunnel construction,” Ren Guoqiang said. The temporary Party branch pooled ideas and, after detailed comparison of schemes such as mixing piles, jet grouting piles, and surface grouting reinforcement, finally chose high-pressure jet grouting piles for water blocking and cement grouting for roof reinforcement. “The construction method was also summarized by us on site, called the three-bench seven-step method,” Ren Guoqiang said. This method divides the entire cross-section excavation into “seven steps,” splitting the tunnel into three benches and adjusting support parameters in a timely manner according to site conditions, ensuring excavation safety to the greatest extent.

The most difficult 180 meters were completed in three and a half months, accumulating valuable experience for future tunnel construction in Fuzhou. Currently, the main structure of the tunnel is complete, and supporting works such as the management building, electromechanical equipment, fire protection, and decoration are being accelerated. To complete the final construction with quality and quantity within one month, four processes—electromechanical, decoration, spraying, and pavement—are advancing simultaneously, with five work faces progressing at the same time in a single tube alone.

Considering the concrete pouring volume in the tunnel reaches 50,000 cubic meters, to ensure supply, the project department also estimated in advance and calculated the demand for 10 days ahead. The owner, the Municipal Urban and Rural Construction General Company, actively coordinated to fully ensure the acceleration of the critical works.