On January 28, the left line of the Jinma section tunnel of Guiyang Rail Transit Line 2, constructed by the Guangzhou Branch of China Railway First Group, was successfully connected, leaving only 52 meters of single-tube excavation on the right line's small mileage before the entire Jinma section tunnel is fully connected.
　　The section between Jinyacun Station and Mawangmiao Station is located in Yunyan District, Guiyang, with a designed left-line length of 1,495.514 meters. After leaving Jinyacun Station, the alignment runs along Baihua Avenue for about 400 meters to Mawang Street, passes beneath the Jinzhong River and the Sanma shantytown redevelopment area, and enters Mawangmiao Station.
　　The landforms along the section consist of alternating karst hills and karst depressions. The strata are mainly dolomite and argillaceous dolomite, with karst caves, troughs, trenches and fissures commonly developed, good connectivity of karst conduits, shallow groundwater depth, and abundant karst fissure water. The section also crosses beneath the Jinzhong River, with only 2 meters of overburden above the tunnel crown. The section was organized for construction via an inclined shaft, with a maximum single-head excavation length of 850 meters. Construction on the main line began in June 2016 and achieved breakthrough despite effective construction time of less than 15 months due to various large conferences, examinations and environmental inspections. The average monthly progress per single heading reached 60 meters, setting a record for tunnel excavation in Guiyang rail transit, while a single roadheader achieved a monthly progress of 210 meters, setting a domestic record for single-machine monthly excavation using a mining roadheader in building tunnel construction.
　　The project team organized construction carefully, optimized the construction plan, overcame numerous difficulties, and ultimately achieved the smooth connection of the left line, laying a solid foundation for the full connection of the Jinma section tunnel.