On September 14, with the last blast, the Qiaopingshan Tunnel—the longest tunnel on the entire Chongqing Railway Hub East Loop Line—was successfully holed through. Overcoming this major difficulty marks a significant victory in the overall construction of the East Loop Line and lays a solid foundation for the completion and opening of the entire line to traffic.

The Qiaopingshan Tunnel is located in Nanquan Town, Banan District, and Changshengqiao Town, Nan'an District, Chongqing, with a total length of 7,568 meters. It is the longest double-track tunnel on the East Loop Line. The main line of the tunnel crosses over the Chongqing-Hunan High-Speed Railway and passes beneath existing highways, buildings, and high-voltage transmission towers. The area it traverses has complex geological conditions, diverse topography and landforms, and numerous existing structures. The tunnel is located at the core of a syncline, and its body mainly passes through the mudstone intercalated with sandstone strata of the Middle Jurassic Shangshaximiao Formation. The mudstone occurs in medium-thick to thin layers, and the surrounding rock is Grade IV and Grade V, indicating poor geological conditions.

Because a passenger train line station is set up inside the Qiaopingshan Tunnel, with turnouts leading to Chongqing East Station, two large-span lining sections of 160 meters and 177 meters in length are designed within the tunnel. The excavation width is 24.53 meters and the height is 15.87 meters. Construction of such a large cross-section, long-section large-span tunnel is extremely rare in the Chongqing area. In addition, floor heave was discovered during the construction preparation period, further increasing the difficulty. As a controlling works point for the entire line, its schedule affects the opening time of the whole line.

To overcome the problems of complex excavation technology, slow progress, and high collapse risk in the large-span section, the relevant units organized four expert demonstration meetings to continuously optimize the double-side drift excavation method for the large-span section. After multiple scheme discussions and model calculations, the excavation method was adjusted to the CD method, the redundant central vertical support was removed, and prestressed anchor bolts with a length of 15 meters and a minimum pull-out resistance of no less than 120 kN were installed at the tunnel crown. The concept of "replacing support with anchors" was adopted to simplify the excavation steps. The project adjusted its techniques according to the optimized scheme, increasing the progress rate of the large-span section from the originally planned 20 meters per month to 43 meters per month. This accelerated the excavation of the large-span section while ensuring safety and won valuable time for the breakthrough of the entire tunnel.

The Chongqing Railway Hub East Loop Line starts in Jiangjin District, passes through Luohuang, Nanpeng, Chayuan, Donggang, Longsheng, Tongjing, Muer, and Shuitu, and ends at Moxinputo North Station on the Xiangyang-Chongqing Railway. The main line has a total length of 155 kilometers. As a key project in Chongqing, once completed, the East Loop Line will connect comprehensive transportation points such as Chongqing railway hub stations and airports, improve the layout of the Chongqing railway hub, enhance the flexibility of transportation organization, meet the logistics and transportation needs of industrial enterprises along the line, guide urban expansion outward, alleviate traffic pressure in the main urban area, accelerate Chongqing's urban construction, promote regional economic growth, and facilitate public travel.