Shanghai-Kunming Expressway starts from Jinshiyu, Liling City at the junction of Hunan and Jiangxi in the east, and ends in Li Yupu, Xinhuang County in the west. * * * It is divided into Liling Lake (Xiangtan), Tanshao Lake (Shaoyang), Shaohuai Lake (Huaihua) and Huaixin Lake (Xinhuang). Among these four sections, the topographic and geological conditions of Shaohuai section are the most complicated. Especially Xuefeng Mountain, which is known as "natural barrier".
Xuefeng Mountain stretches for hundreds of kilometers, and the main peak is 1934 meters above sea level. It is located between Shaoyang and Huaihua in the southwest of Hunan Province, with criss-crossing ravines, towering peaks, steep mountain passes, many deep valleys between ridges and surrounded by rivers and streams. 30 km highway crossing the top of the mountain, with curve 33 1 and dangerous situation 122. The local folk song says: "Xuefeng Mountain, the mountain is connected with the mountain, 33 1 bend, 33 1 pass, and the pass is a' ghost gate'". Crossing Xuefeng Mountain has become a "gray section" in the minds of drivers and passengers in the past. People are eager for cars to cross the mountains like armor.
The highway starts from Zhouwangpu Interchange at the end of Tan-Shao Expressway, passes through Longhui, Dongkou County of Shaoyang City and Hongjiang, he cheng and Zhong Fang counties (cities and districts) of Huaihua City, and ends in Zhutian, Zhong Fang County, connecting with Huaihua-Xinhuang Expressway. It spans Zijiang, Yuanshui and Xuefeng Mountain. The length of the main line is 155.69 km, and there are bridges such as extra large bridges and viaducts 199. The length of a single tunnel is more than 70 km, and there are 14 tunnels, and the length of a single tunnel is more than 30 km. The length of tunnels and bridges is close to one third of the whole line. The whole line is built according to the standard of two-way four-lane expressway. The project investment is 8.36 billion yuan. With a construction period of 48 months, it was the largest and most difficult highway construction project in Hunan Province at that time. On September 19, 2003, the groundbreaking ceremony of Shaohuai Expressway was held in Zhong Fang County, Huaihua City. The geological conditions of Xuefeng Mountain Tunnel are particularly complicated. According to the preliminary investigation, it is estimated that there are 18 fracture layers, and 18 fracture layers are found during the construction, all of which are large regional fracture layers above Grade III. It is expected that there will be gushing springs in the early stage. In this way, not only will there be frequent springs, but there will also be a lot of groundwater. The technical difficulty of construction is rare in domestic tunnel construction. Under the coordination and guidance of Shao Huai Company and Shao Huai Highway Director's Office, through the cooperation with relevant professional institutes, the technical problems encountered in Xuefeng Mountain tunnel construction have been solved, and at the same time, the advanced experience of tunnel construction at home and abroad has been used for reference. At present, the most advanced "NATM" in China is adopted for construction, that is, controlled blasting is the main driving method, anchor rod and shotcrete are the main supporting methods, and theory is combined with measurement and experience. Thin-layer support is used to restrain the deformation of surrounding rock, maintain its strength and give full play to its bearing capacity. And always keep in mind and follow the tunnel construction concept of "caring for surrounding rock, inner beauty, paying attention to environment and dynamic construction" and the tunnel construction principle of "controlling water first, controlling short opening, weak blasting, forcing payment, early lining, diligent inspection, diligent measurement and steady progress".
The main practices of Guizhou Bridge Engineering Corporation in Xuefeng Mountain Tunnel construction can be summarized as follows: using laser profiler to draw smooth blasting holes around, and adhering to smooth blasting technology; Use geological radar to detect the surrounding rock in front and insist on forecasting; Insist on monitoring and measuring the surrounding rock after excavation, and take strain measures at any time to improve the excavation accuracy; Grouting reinforcement and steel arch frame are used to pass through the fault fracture zone safely; Water injection mud-sodium silicate double liquid mud is used to block water, reduce groundwater loss and protect the environment; Popularization and application of three-dimensional waterproof net to guide water has achieved good results in lining waterproof and drainage; Use high-voltage armored cable to enter the tunnel to ensure the safety of construction equipment; In the construction of ventilation inclined shaft of long tunnel with large inclination angle, winch is used for the first time to cooperate with lifting transportation. It is their courage to innovate, vigorously popularize and apply new technologies, overcome difficulties and key points in construction, rationally use advanced instruments in construction, and all engineers carefully construct, so as to realize and ensure the safety, quality, progress and final accurate penetration of Xuefeng Mountain Tunnel construction.
Xuefeng Mountain Tunnel was completed in August 2006, and officially opened to traffic with Shaohuai Expressway (Shaoyang to Huaihua) in June 2007. Xuefeng Mountain Tunnel is known as a "natural barrier" because of its dangerous terrain, criss-crossing ravines and towering peaks. To build a tunnel here, not only the construction site is extremely narrow, but also the geological conditions are extremely complicated and the construction is very difficult. The tunnel started construction in April, 2002. It is divided into two lines, and four construction teams excavate from the east and west at the same time. Due to the adoption of high-tech technologies such as satellite positioning, the lateral error is zero millimeters and the elevation error is only seven millimeters, and the penetration accuracy has reached the highest level in China. Peng Limin, a tunnel expert in China, said that the nearly seven-kilometer-long tunnel had no casualties or collapses during the whole construction process, which is also rare in the history of tunnel construction in China.