Recently, with the breakthrough of the Shangshan Tunnel, the last dedicated tunnel for a long-distance natural gas transmission pipeline crossing the Qinling Mountains, all 105 tunnels along the Zhongwei–Zaoyang section of the middle leg of PipeChina's West-East Gas Pipeline III have been holed through, marking a breakthrough progress in the project.

The Zhongwei–Zaoyang section of the middle leg of the West-East Gas Pipeline III starts from the Zhongwei interconnection compressor station in Ningxia, passes through five provinces and autonomous regions—Ningxia, Gansu, Shaanxi, Henan and Hubei—and ends at the Zaoyang interconnection compressor station in Hubei, with a total length of 1,264.1 km. Of this, 311 km of pipeline runs through the hinterland of the Qinling Mountains, known as the "National Central Park," an area that is a key focus of ecological protection in China. PipeChina adopted the tunnel-crossing construction method to avoid damaging surface soil to the greatest extent and to reduce the impact of construction on the natural environment.

Construction site

According to reports, the tunnel crossings took 24 months, with a total excavation length of 113 km, making the Zhongwei–Zaoyang section of the middle leg of the West-East Gas Pipeline III the project with the largest number of tunnel crossings in China's long-distance oil and gas pipeline construction.

The Qinling Nature Reserve features steep mountains, complex terrain, poor accessibility, and weak social support. Mountain weather is changeable, and natural disasters such as floods and debris flows occur frequently. At the same time, tunnel construction and pipeline installation were carried out in parallel and cross-operation, posing great challenges to the project schedule and to quality, safety and environmental control. PipeChina adhered to the "one tunnel, one plan" approach, integrated the relevant requirements of "environment, water and conservation" into daily management, and conducted research on a combined mechanical excavation and drill-and-blast method tailored to the complex and variable geological surrounding rock and the construction characteristics of small-section tunnels, thereby increasing tunnel excavation speed through technological innovation.

The Shangshan Tunnel holed through this time has a total length of 6.03 km. Located in the Qinling Nature Reserve, it passes through the Shangshan Forest Park in Shaanxi Province, and its exit is close to the Cliff Tomb historic site and the Danfeng Danjiang National Wetland Park. It is the longest tunnel in the entire project. PipeChina adopted the shield TBM (tunnel boring machine) method for construction, which offers advantages such as good safety, high construction efficiency, and low vibration and noise. On the premise of effectively ensuring project quality and safety, it reduced the construction period to 23 months, significantly saving time compared with the traditional drill-and-blast tunneling method, minimizing the impact of tunnel construction on the air, acoustic and water environments, and effectively protecting the diversity of wild animals and plants.