On January 19, as the Spring Festival approaches, the NCZQ2 project department of the China Railway 14th Bureau Group's new Nanning-Chongzuo Railway brings good news. As of January 18, the main structure of the large-mileage open-cut section of the Liucun Tunnel—a key node of Guangxi's new Nanning-Chongzuo Railway and the region's first large-diameter railway shield tunnel—has been completed; shield tunneling has also reached 2,080 meters, passing the halfway mark.

The Liucun Tunnel is being built by Guangxi Communications Investment Group Co., Ltd. and constructed by China Railway 14th Bureau Group. The shield tunnel passing the halfway mark in excavation marks a breakthrough in the project's construction, laying a solid foundation for the project's smooth completion by the end of 2021 and providing scientific data for building Guangxi's large-diameter shield technology standards system.

The Liucun Tunnel has a total length of 5,725 meters, including a 1,240-meter large-mileage open-cut section, a 479-meter small-mileage open-cut section, and a 4,006-meter shield section. It passes beneath six existing railways and one subway line, crosses 12 building clusters and 27 underground pipelines of various types. As Guangxi's first large-diameter railway shield tunnel, it adopts internationally leading large-diameter shield tunnel construction technology, attracting widespread attention in the engineering industry and standing out as a project with distinctive regional characteristics in Guangxi.

Yang Fan, manager of the shield work area of the NCZQ2 project department of the China Railway 14th Bureau Group's new Nanning-Chongzuo Railway, said the shield machine used for the Liucun Tunnel is a slurry balance shield machine with an excavation diameter of 12.86 meters. During excavation, workers encountered many construction difficulties, such as sluggish discharge of muck in the chamber, severe tool wear, excessively high mud specific gravity, sudden encounters with hard rock strata, passing beneath numerous urban buildings, and high requirements for surface settlement control, posing enormous construction risks.

Although the project team's key technical personnel have participated in the construction of highly difficult projects such as the Nanjing Yangtze River Tunnel, the Xiamen Line 2 sea-crossing tunnel, and the Qinghuayuan Tunnel on the Beijing-Zhangjiakou high-speed railway, and have rich experience in crossing rivers, lakes, seas, bustling urban areas, and old shantytowns, they still dare not slacken in the slightest, boldly innovating during construction and continuously solving problems.

In response to the various difficulties encountered during construction, the project department held multiple meetings with internal and external experts. Through measures such as equipment modification, tool replacement via compressed-air chamber entry, adjustment and control of excavation parameters, and adjustment of mud specific gravity, shield construction has achieved stability, safety, and continuity. At present, the shield machine is advancing steadily at a rate of 12 meters per day, ensuring the tunnel is fully holed through before the end of August 2021.

Yang Fan said the biggest difficulty this year is crossing beneath the Yungui Railway and constructing a 1,200-meter circular curve radius. Workers will adjust excavation parameters in a timely manner according to the circular curve radius and conduct 24-hour monitoring during construction beneath the Yungui Railway to ensure construction safety and quality.

Xie Xu, manager of the civil engineering work area of the NCZQ2 project department of the China Railway 14th Bureau Group's new Nanning-Chongzuo Railway, said the large-mileage open-cut section began construction in March 2019 and is scheduled for completion in June 2021. Located beneath Liucun Road, it crosses over Metro Line 4 and passes beneath Nahong Avenue. The construction front is long, with residential and commercial clusters on both sides. By continuously improving traffic diversion plans and optimizing construction organization, the project department's technical personnel overcame difficulties such as a narrow construction site, high difficulty in organizing construction, and serious water leakage between piles. At present, the large-mileage open-cut section has completed 75% of the planned tasks. The main structure has been completed and is now in the road surface backfilling and restoration stage. The next stage will move on to the construction of tunnel auxiliary structures, drainage ditches, and cable troughs.

It is reported that the new Nanning-Chongzuo Railway has a main line length of 119.3 kilometers and a designed operating speed of 250 kilometers per hour. It is an important part of the railway corridor from Nanning, the capital of Guangxi, to the border city of Pingxiang, and also an important transportation route for Guangxi to deeply integrate into the "Belt and Road" initiative, fully realize the construction of an international corridor facing ASEAN, and create a new strategy for opening up and development in South China. Once the railway is completed and opened to traffic, the travel time from Nanning to Chongzuo will be shortened from the current 2 hours to half an hour, achieving the goal of high-speed rail access in all cities of Guangxi.