At 11 a.m. on July 26, a 32-meter-long, 900-tonne box girder was steadily placed on the designated pier of the Chengjiang Double-Track Grand Bridge on the Guiyang-Nanning High-Speed Railway, marking the smooth completion of the bridge, which is the longest on the entire line, has the widest continuous girder span, and involves the largest volume of assembled girders. With this, the overall progress of bridge works on the Guangxi section of the Guiyang-Nanning High-Speed Railway has exceeded 80%, and the project has fully entered the accelerated final stage and the stage of reinforcing bridge deck facilities, preparing for the subsequent construction of the ballastless track bed.

▲The completed Chengjiang Double-Track Grand Bridge (photo courtesy of China Railway Beijing Engineering Group)

▲At the commander's order, the last box girder of the Chengjiang Double-Track Grand Bridge is slowly lowered into position

▲Workers installing bearing bolts for the last box girder of the Chengjiang Double-Track Grand Bridge

The Chengjiang Double-Track Grand Bridge is located in Du'an Yao Autonomous County, Hechi City, Guangxi. With a total length of 15.5 kilometers, it is the longest bridge on the entire Guiyang-Nanning High-Speed Railway and among all existing railway bridges in Guangxi. In the later stage of box girder erection, as the distance between the girder fabrication yard and the erection site grew increasingly long, transporting a single box girder took more than six hours. Because this period coincided with the "dog days" of high temperature and severe heat, the girder transporter, operating at high power for long periods under full load, was prone to breakdowns that could affect bridge erection.

To ensure construction progress, the participating units—Yungui Railway Guangxi Company and China Railway Beijing Engineering Group—adopted a construction plan of "transporting at night and erecting during the day," scheduling girder transport during the cooler early morning hours to ensure that girders were delivered to the designated locations for laying and erection before noon. After the construction plan was optimized, the failure rate of the girder transporters dropped by 60% compared with before, effectively safeguarding the girder erection progress.

▲During girder erection, workers confirm the girder placement position in real time

The Chengjiang Double-Track Bridge crosses the Lanhai Expressway, the Chengjiang National Wetland Park, and the Du'an Chengjiang River Class II Water Source Protection Zone, making construction highly difficult. To ensure that the Lanhai Expressway was not affected by construction, the participating units designed a 180-meter arch-stiffened long-span continuous girder—currently the widest span of its kind in Southwest China—for the section crossing the expressway, spanning the Lanhai Expressway in a single pass and minimizing the impact of construction on highway traffic. In addition, for the section that crosses the wetland and water source protection zone in a concentrated manner, 46 segmental assembled girders were designed, making it currently the largest segmental assembled girder project in China. Compared with traditional box girders, segmental assembled girder construction can be carried out entirely on the girder surface, offering clear environmental advantages. This technique is the first of its kind in the history of railway bridge construction in Guangxi. Throughout the entire construction process, no congestion or slow traffic occurred on the Lanhai Expressway section due to construction, and no complaints were received concerning environmental pollution caused by the bridge construction.

As of now, the subgrade earthwork on the Guangxi section of the Guiyang-Nanning High-Speed Railway has reached 85% of the total design volume, bridge works 80%, and tunnel works 76%. In the second half of this year, bidding will begin for the later-stage high-speed railway construction works, including station buildings and the four electric systems (communication, signaling, power supply, and electrification).

The Guiyang-Nanning High-Speed Railway runs through northwestern Guangxi and southeastern Guizhou. It is the first high-speed railway in Guangxi designed for a speed of 350 kilometers per hour and an important component of the new north-south land corridor under the Belt and Road Initiative. It is of great significance for Guangxi in advancing the construction of the New Western Land-Sea Corridor and accelerating the establishment of a new open development pattern featuring "southward outreach, northward linkage, eastward integration, and westward cooperation." The full line is expected to open by the end of 2023. By then, travel time between Nanning and Guiyang will be shortened to just over two hours.