On March 8, the tunnel works of the Hongfan Depot of Section 5 of the Phase 4 West Extension of Chongqing Rail Transit—Chongqing's first "dual-track, double-deck" depot—constructed by PowerChina's Sinohydro Bureau 9 Co., Ltd., achieved full breakthrough ahead of schedule, laying a solid foundation for the project's goal of full opening to traffic in 2025.

The construction content of Section 5 of Chongqing Rail Transit Line 4 mainly comprises one Hongfan Depot, one Hongfan Road main substation (co-built with the depot), and a 1,006.146-meter depot access line section. The Hongfan Depot is Chongqing Rail Transit's first "dual-track, double-deck depot," equipped with 15 stabling and inspection tracks and 1 car-washing track. The Hongfan Depot includes six individual structures: the operations building, the throat area, the comprehensive maintenance building (including driver apartments and a canteen), the wastewater treatment station, and the garbage station. The operations building is arranged facing the operations building of the Hongfan Depot of Line 21 in a double-deck stacked configuration.

The tunnel works completed this time mainly fall within the construction of the depot access line section, where the construction area has dense building clusters, interlaced underground pipelines, and unstable rock strata. During construction, the project team independently researched and applied an integrated construction technology system of "mechanized excavation + digital monitoring + information-based dynamic construction design," using intelligent excavation equipment to replace traditional blasting processes and greatly reducing vibration impacts on the surrounding environment. At the same time, through a digital monitoring system, data such as tunnel deformation and surrounding rock stress were collected in real time, and combined with information-based dynamic construction design, the construction plan was adjusted promptly, successfully bringing complex geological risks under control and achieving a dual breakthrough in safety and efficiency.

In project management, given the characteristics of numerous construction points, large working faces at each point, extensive cross-operation among points, and complex process construction, the project team established a three-dimensional management model of "grid-based management + team building + multi-disciplinary coordination" tailored to local conditions. By dividing the construction area into refined grid units, assigning clear responsibilities to individuals, and strengthening standardized team building, they created a construction workforce with strong skills. At the same time, a cross-disciplinary coordination platform was established to coordinate the interwoven operations of civil engineering, mechanical and electrical works, track works, and other disciplines, ultimately achieving the goal of increasing average daily excavation efficiency by 20% over the original plan, providing strong support for the early full breakthrough of the tunnel works.

The Phase 4 West Extension of Chongqing Rail Transit Line 4 passes through Jiangbei District and Yubei District of Chongqing. Once completed, it will operate through with Phase 1 and Phase 2 of Chongqing Rail Transit Line 4, further densifying the rail transit network in Chongqing's central urban area and making travel more convenient for residents.