On the morning of the 3rd, with a resounding blast, the Deqing Tunnel—the highest rock-stratum risk-level tunnel on the Guiyang-Nanning High-Speed Railway—was successfully holed through two months ahead of schedule. This also marks the successful resolution of the biggest challenge in the entire line's tunnel works, pressing the "fast-forward button" for the final breakthrough of the remaining tunnels.

According to reports, the Deqing Tunnel is located in Hechi City, Guangxi. With a total length of 6,610 meters, it is a key controlling project of the entire Guiyang-Nanning High-Speed Railway and the highest risk-level tunnel on the line. The Deqing Tunnel passes through a typical karst landscape area, with nearly half of its tunnel body surrounded by Grade V surrounding rock—the least stable rock stratum—and unfavorable geological features such as karst caves, karst grooves, and dissolution-fractured zones are found everywhere. On average, there is one karst cave every 50 meters of excavation, and the entire tunnel contains more than 200 karst caves and cavities, making construction highly difficult. The tunnel also has nearly 2,000 meters of roadbed in deep, thick clay layers with very poor bearing capacity; if such swamp-like soil layers are not handled properly, they can easily cause subsidence and depression.

During construction, the builder adopted the "smooth blasting method," the most advanced technique in domestic high-speed railway tunnel construction. It produces fewer flying rocks and can create a smooth blasting face. At the same time, 3D scanners can be used to collect rock-stratum data and analyze it in real time, calculating and optimizing the quality, spacing, explosive distribution, and charge quantity data of the tunnel blasting holes, effectively ensuring the stability of the rock strata around the tunnel.

In addition, the tunnel foundation pile-raft structure construction technique was adopted, driving more than 1,000 pile foundations in the clay layer sections and then laying sturdy raft slabs. These reinforced concrete pile foundations and raft slabs feature high bearing capacity and small settlement. As a result, the biggest challenge in the entire line's tunnel works was successfully resolved.

It is understood that the Guiyang-Nanning High-Speed Railway spans northwestern Guangxi and southeastern Guizhou. It is Guangxi's first high-speed railway designed for a speed of 350 kilometers per hour, and the entire line is expected to open for operation by the end of 2023, when travel time from Nanning to Guiyang will be shortened to more than two hours. As of now, the Guangxi section of the Guiyang-Nanning High-Speed Railway has completed 85.6%, 81%, and 78% of the designed totals for subgrade earthwork, bridge works, and tunnel works, respectively. Of the 45 newly built tunnels, 31 have been successfully holed through. In the second half of this year, bidding work is planned to start for the later-stage high-speed railway construction projects, including station buildings, communications, signaling, and power supply.