At 5:18 p.m. on June 14, the Yanjiazhai Tunnel on Section 4 of the Guizhou portion of the Guinan High-Speed Railway, constructed by China Railway 11th Bureau Group, was successfully holed through, a full 18 days ahead of the original schedule.

The Yanjiazhai Tunnel is located in Dushan County, the "southern gateway" of Guizhou. With a total length of 1,670 meters, the tunnel passes through complex and changeable geological and topographic conditions. The tunnel entrance connects from the Lajuan double-track super major bridge and the Lagan double-track super major bridge, while the exit links via the Dushandong high-speed railway station building to the Datiangeng super major bridge and the Jinwozhai No. 1 and No. 2 super major bridges. Situated at the central position of the girder-erection passage, it was a "roadblock" standing in the way of girder erection.

The Yanjiazhai Tunnel not only has complex geological conditions, but its surrounding environment also imposed many restrictions on construction: the first half of the tunnel passes beneath a six-lane urban dual carriageway, and villages and residential buildings of various sizes are located around the alignment, placing high demands on construction organization and safety.

During construction, the Project Department of Section 4 of the Guizhou portion of the Guinan High-Speed Railway under China Railway 11th Bureau Group actively communicated and coordinated with the local government, optimized the plan, adopted a two-way traffic scheme on a single-side lane, closed one lane in advance, and built a Bailey beam temporary bridge on the other lane to ensure normal vehicle traffic. Controlled blasting excavation was used during construction, with repeated calculation and simulation to precisely determine the amount of explosives and strictly control blasting energy and scale, thereby ensuring the blasting effect while minimizing the impact of construction on surface road traffic and the surrounding residential environment.

It is understood that Section 4 has a total of 6 tunnels, of which 4 have been holed through so far. The remaining two, the Dushan No. 2 Tunnel and the Changpo No. 2 Tunnel, are scheduled to be holed through in December this year and August next year, respectively.

On the eve of July 1, the Project Department of Section 4 of China Railway 11th Bureau Group will begin girder erection as a tribute to the 100th anniversary of the founding of the Communist Party of China.

The Guinan High-Speed Railway is a component section of the Baotou-Haikou Corridor (Baohai Corridor) of the "Eight Vertical and Eight Horizontal" high-speed railway network in China's Medium- and Long-Term Railway Network Plan. It is Guizhou's first double-track high-speed railway with a design speed of 350 kilometers per hour, connecting Guizhou and Guangxi provinces (regions), with a main line length of 481.118 kilometers, of which the Guizhou section is 199.64 kilometers long. A total of 189 bridges need to be erected along the entire line, including 84 in the Guizhou section; and 107 tunnels need to be holed through, including 63.5 in the Guizhou section. The bridge-tunnel ratio of the entire line (the proportion of bridge and tunnel length to the total line length) exceeds 91%. The entire line is expected to be ready for opening by the end of 2023.

After the entire Guinan High-Speed Railway is opened, the travel time by EMU train from Guiyang to Nanning will be reduced from the current more than 5 hours to less than 2 hours, playing an important role in promoting rural revitalization and high-quality economic and social development along the line.