It was learned on November 18 that the first tunnel of the Phase I civil engineering works of Chongqing Rail Transit Line 15—the mined section II of the access line to the Tongluoshan Depot—has been officially and smoothly holed through, marking the first tunnel to be completed across the entire Phase I project of Chongqing Rail Transit Line 15.

At the project site, the tunnel was seen fully holed through on both sides. At the entrance, several workers were carrying out slag removal and dust control work. Deep inside the tunnel, a large excavator continued to excavate the road surface in preparation for the next stage of construction.

It is reported that the completed tunnel has a total length of 85 meters and is a single-tube, double-track tunnel. The tunnel's surrounding rock dip angle, the shallow cover at the tunnel crown, and its proximity to existing roads are unfavorable to construction, posing certain construction difficulties.

Since excavation began in September, the construction contractor has rationally adjusted the sequencing between processes, scientifically allocated resource elements, strengthened routine safety inspections, and, during blasting in the shallow-buried section, closely monitored blasting vibration velocity and effects, dynamically adjusted the blasting plan, improved smooth blasting results, and ensured the quality and safety of tunnel construction.

The breakthrough of this tunnel provides valuable construction experience for the subsequent construction of long tunnels and also lays a solid foundation for the follow-up construction of the access line to the Tongluoshan Depot and the smooth opening of the entire line.

According to the introduction, the Phase I project of Line 15 has a total length of approximately 38.73 kilometers and a construction period of six years. The project starts at Jiuquhe East Station in Liangjiang New Area, passes through Jintong Road Station and Southwest University of Political Science and Law Station, and is mainly located in Liangjiang Movie City. It has 14 stations, all underground, including 7 transfer stations, with an average station spacing of 2.96 kilometers. It is currently the first urban express rail project in China with a speed of 140 kilometers per hour to be implemented. Once put into operation, it will connect the Liangjiang New Area Administrative Committee, Terminal 3 of Jiangbei International Airport, Liangjiang Movie City, and other locations.

After the Phase I project of Chongqing Rail Transit Line 15 is completed and put into use, it will further facilitate travel for residents of Liangjiang New Area and accelerate the area's integration into a new pattern of smooth, interconnected, fast, and efficient transportation.

It is reported that the so-called urban rail express line is a new type of rapid rail transit that provides fast, high-capacity, and bus-style services for commuting. It has large station spacing, usually about 3 kilometers. Compared with conventional urban rail lines, it has higher operating speeds, with a design speed of 120–160 kilometers per hour, and operates through with regional (suburban) railways, organically connecting with the urban rail transit network to achieve multi-point transfers. It mainly serves the construction of a "one-hour commuting circle" between the central urban area and the main urban new areas.

It is worth mentioning that the Phase II project of urban rail express line 15 officially started construction a few days ago. The Phase II project starts at Zengjia Station, passes through University City Middle Road Station, Jinshan Temple Station, Happy Valley Station, and other stations, and ends at Jiuquhe East Station of Phase I of urban rail express line 15.

After the Phase II project of urban rail express line 15 is completed, it will link Shapingba District, Liangjiang New Area, and Yubei District from west to east, connecting three major transportation hubs: the Science City railway hub, Chongqing Jiangbei International Airport, and Fusheng High-Speed Railway Station. It is of great significance for further improving the structure and hierarchy of Chongqing's rail transit network, promoting the integrated high-quality development of the main urban metropolitan area, and guiding the urban development pattern.