On September 17, the exit of the Baimashan Tunnel on the Chongqing-Qianjiang Railway, in whose construction China Railway 11th Bureau Group participated, was successfully holed through, marking the smooth joining of the tunnel exit with No. 2 cross adit. This represents a phased breakthrough in project progress and lays a solid foundation for the early opening of the entire line to traffic.

The Baimashan Tunnel is located within Wulong District, Chongqing Municipality. It runs obliquely through Lingshan Village, Baima Town, Wulong District on the west side, extends in a north-east direction, obliquely crosses the Da'ershan anticline at Nongfeng Village, extends toward the south-east, and emerges near Nongguang Village, Yangjiao Town, Wulong District. The entire tunnel is 13,407 meters long and adopts a "人"-shaped (inverted-V) gradient design, with a maximum burial depth of approximately 903 meters.

The Baimashan Tunnel is the longest tunnel on the entire line and a controlling project for the whole line. The tunnel's geological conditions are complex, combining adverse geology such as high gas, karst water inrush, toxic and harmful gases, and fault fracture zones, and it has been classified as a Grade I high-risk tunnel. During construction of the tunnel exit, difficulties posed by adverse geology such as landslides of the slope deposit at the portal, shallow cover and unbalanced pressure, and fault fracture zones were overcome, and the tunnel was holed through on schedule. This laid a good foundation for the subsequent in-tunnel ancillary works and ballastless track construction, and ensured the normal progress of construction organization across the entire line.

To ensure the safe and smooth holing-through of the Baimashan Tunnel exit, the Chongqing-Qianjiang Section 7 project team solidly carried out safety production work and steadily advanced construction progress. During construction, the project continuously optimized construction plans and actively explored informatized and intelligent high-efficiency construction throughout the entire tunnel construction process, promoting mechanized, informatized, and intelligent construction across all tunnel procedures. Fully automatic gas monitoring equipment was installed inside the tunnel, and advanced detection methods were used to carry out advanced detection and judgment of tunnel geology. To solve the problem of voids at the crown of the tunnel lining, pressure-contact sensors were applied inside the tunnel for the first time, greatly improving tunnel construction quality and efficiency and providing safety assurance for tunnel construction. In addition, the project established a safety and quality guarantee team to vigorously pursue safety protection and quality control, taking the creation of a premium project as the ultimate goal, so that this milestone task was successfully completed.

The Chongqing-Qianjiang Railway is an important component of the Xiamen-Chongqing corridor in the national "Eight Vertical and Eight Horizontal" high-speed rail network plan, and is the south-east high-speed rail corridor in Chongqing's "米"-shaped high-speed rail network. The Chongqing-Qianjiang Railway is designed for a speed of 350 kilometers per hour. After completion and opening to traffic, it will achieve one-hour high-speed rail connectivity between the Chongqing main urban area and the Wuling Mountain urban cluster in southeast Chongqing. It is of great significance for deeply implementing the Yangtze River Economic Belt development strategy, improving the layout of the high-speed railway network, accelerating the formation of the main high-speed railway corridor from Chongqing to Xiamen, and driving economic and social development along the route.