en.Wedoany.com Reported - The Quanmutang Reservoir, the largest single water conservancy project in Hunan Province, China, has achieved a key milestone as its controlling project, the Jiulongling Tunnel, broke through on June 28. Constructed by China Railway No.5 Engineering Group Co., Ltd., the tunnel is the core section of the reservoir's irrigation area water conveyance channel.
Listed among China's 172 major water conservancy projects, the Quanmutang Reservoir is also the largest water conservancy project in Hunan since the founding of the People's Republic of China. Located in the upper and middle reaches of the Zi River in Shaoyang City, its irrigation area covers the core region of the Hengyang-Shaodong arid corridor. The Jiulongling Tunnel traverses the watershed between the Xiang River and the Zi River, with a main tunnel length of 19.82 km, making it the longest water conveyance tunnel completed in Hunan Province. Lot II, undertaken by China Railway No.5 Engineering Group Co., Ltd., includes a 10.4-km main tunnel and four construction adits totaling 3.36 km, with a maximum burial depth exceeding 300 meters. This section features highly developed karst formations, interlaced underground rivers, and densely distributed large cave clusters, making it the most complex in hydrogeology and the highest in construction risk and difficulty across the entire tunnel.
The project officially commenced on July 18, 2020, with a construction period of nearly six years. Throughout the construction, the tunnel continuously encountered extreme geological challenges such as fault fracture zones, extremely soft surrounding rock, high-pressure water inflows, and large-scale mud bursts. A total of 8 large dissolution caves were discovered, with various adverse geological sections distributed continuously, repeatedly hindering construction. The project team adopted a treatment strategy of "comprehensive exploration, avoiding inferior conditions, and overcoming difficulties through route adjustments," implementing 9 local realignments to bypass large karst structures. Through a combination of measures including "drainage, plugging, bypassing, and grouting," they completed 4,411 meters of advanced grouting for water blocking, effectively mitigating high-risk hazards such as water and mud inrushes and tunnel instability. During construction, over 20 on-site expert consultations were held to evaluate solutions, and additional adits were built to alleviate construction pressure. After 2,171 days and nights of continuous work, the Jiulongling Tunnel achieved a safe breakthrough without any quality or safety incidents.
