After more than 740 days and nights, at 8:31 a.m. on May 21, the right tube of Deqing Tunnel on the Tongren–Sairilong (Qinghai–Gansu border) section of the G0611 Zhangye–Wenchuan National Expressway was successfully holed through. This is the second tunnel to be holed through in succession this month, following the breakthrough of the left tube of Zong'an Tunnel on May 16.

Deqing Tunnel of the Tongsai Project Successfully Holed Through

It is understood that the tunnel sites of Deqing and Zong'an tunnels lie in a tectonic denudation low-to-medium mountain landform unit, where exposed rock and soil masses are commonly seen, only a small amount of weeds are distributed, and vegetation is poorly developed. The terrain is steep, the working space for tunnel portal and exit operations is narrow, and excavation control of the portal side and face slopes is relatively difficult. Meanwhile, the tunnel strata from top to bottom are successively slope-wash gravelly soil, strongly weathered sandstone intercalated with slate, and moderately weathered sandstone intercalated with slate. The geology is complex and variable. Affected by pore phreatic water in loose layers and bedrock fissure water, the surrounding rock of the tunnel as a whole is weak and broken and softens severely upon contact with water. The construction procedures and support parameters of the tunnel body require dynamic design, construction control is difficult, and safety risks are high.

Zong'an Tunnel of the Tongsai Project Successfully Holed Through

Since construction began on the two tunnels, Deqing and Zong'an, the participating units have focused on overcoming difficult factors such as the frigid, high-altitude climate and extremely complex geological conditions. They have organized scientifically, vigorously pursued safety, quality and schedule management, strengthened management and control of advance geological forecasting, promptly carried out comprehensive judgment and analysis of geological conditions, and identified in advance the location, nature and scale of unfavorable strata. In accordance with the requirements of "dynamic design and dynamic control," they scientifically adjusted construction parameters and excavation techniques, and orderly overcame the difficulties of weak, broken surrounding rock and complex, variable geology. The construction targets were completed ahead of schedule, laying a solid foundation for building a "Safe Century Quality Project" and achieving the early completion of the Tongsai Project.

The Tongren–Sairilong (Qinghai–Gansu border) section of the G0611 Zhangye–Wenchuan Expressway is a key project in Qinghai Province. It connects Qinghai and Gansu provinces and is an important section of the "Vertical Line One" Zhangye–Henan Expressway within the "Three Verticals, Four Horizontals and Ten Connecting Lines" (abbreviated as the "3410 Network") of Qinghai Province's expressway network as defined in the Qinghai Provincial Trunk Highway Network Plan. Project construction plays an important role in thoroughly implementing the Western Development and "Belt and Road" development strategies, accelerating the improvement of the national expressway network, improving regional traffic conditions and alleviating regional traffic congestion. It is of great significance for advancing transport connectivity in the border area of Qinghai, Gansu and Sichuan and achieving balanced development.