On March 26, the Jinyun Mountain Tunnel in the Bihu section of Rail Transit Line 27, invested in and constructed by Chongqing Transportation Development & Investment Railway Group and built by Sinohydro Bureau 4 of Power Construction Corporation of China, was successfully holed through. It is the first long, mountain-crossing tunnel on the entire line to be completed, marking a major milestone in the construction of Rail Transit Line 27 and laying a solid foundation for the smooth opening of the line.

　　The left-line Jinyun Mountain Tunnel is a double-tube, single-track tunnel with a total length of about 3.2 kilometers. The tunnel passes through complex geological structures with alternating layers of various rock and soil types and abundant groundwater. It has successively crossed more than 26 high-risk construction areas, including large coal-mine goafs, faults, fracture zones, gas, and water-rich karst development zones, and is classified as a high-risk project under key monitoring. To overcome construction difficulties, the contractor Sinohydro Bureau 4 organized expert guidance, optimized construction organization, strengthened construction techniques, and strictly controlled safety and quality red lines. It also set up a professional advanced geological forecasting team to accurately detect geological conditions, develop targeted technologies, and prepare targeted plans and construction methods. The tunnel was safely holed through 11 months ahead of the expected schedule, laying a solid foundation for subsequent construction.

　　To further improve construction efficiency, the project Party branch gave full play to the role of grassroots Party organizations as fighting fortresses and the vanguard and exemplary role of Party members. On the basis of scientifically and reasonably setting construction goals, it organized and promoted the "Party Building + N" working model to boost high-quality production and construction. Through approaches such as Party building + safety and Party building + quality, and with the annual labor competition as a carrier, it gave play to the vanguard role of Party member demonstration posts and Party member commando teams, set up various deliberative and coordinating bodies such as a special leading group, a technical expert support group, and a comprehensive coordination support group, promoted the integration of Party building into project construction, focused on monitoring key and difficult issues in tunnel construction, and vigorously advanced tackling of key challenges and high-quality contract performance, achieving cost reduction and efficiency improvement in project construction.

　　The successful holing-through of the Jinyun Mountain Tunnel has laid a solid foundation for the smooth opening and operation of Rail Transit Line 27. After the project opens to traffic, it will quickly connect Bishan District, Chongqing High-tech Zone, Shapingba District, Jiulongpo District, Yuzhong District, Nan'an District, and Banan District, link important gateway hubs such as Shapingba Station, Chongqing Station, and Chongqing East Station, and realize rapid transfer between internal and external urban transportation. This is of positive significance for Chongqing to accelerate the building of a modern, high-quality comprehensive three-dimensional transportation network.