On July 6, after seven years of hard work, Muzhailing Extra-long Tunnel, the control project of Weiwu Expressway, which was built by China Railway Tunnel Bureau, was successfully completed, laying a solid foundation for the opening of Weiwu Expressway by the end of the year.
Muzhailing Extra-long Tunnel is 15.2 kilometers long, with a two-way four-lane design and a maximum design speed of 80 kilometers per hour. A tunnel of 15.2 kilometers can be opened in two or three years under conventional geological conditions, but it took more than seven years in Muzhailing. What are the difficulties in the construction of this tunnel?
According to the technical specialist of China Railway Tunnel Bureau, Muzhailing Extra-long Tunnel is located at the junction of four major geological plates, which have strong tectonic activities, making the already weak carbonaceous slate more broken. During the construction process, the large deformation of soft rock in the tunnel is very serious, the extrusion deformation rate is fast, the deformation duration is long, the deformation amount is large, and the maximum unilateral deformation of the tunnel exceeds 2000 mm, which refreshes the domestic record. It is difficult to predict the change law of surrounding rock
because the deformation magnitude of carbonaceous slate, which is
"melting in wind and melting in water", has exceeded the cognitive level of rock mechanics theory and tunnel construction practice followed by tunnel and underground engineering circles at home and abroad, and has exceeded the scope of current norms and standards. There is no successful experience for reference in design and construction, which is called "a rare worldwide problem in the history of tunnel construction" by academicians, experts and scholars in the field of underground engineering in China. On the basis of summing up the construction experience of Muzhailing Tunnel on Lanzhou-Chongqing Railway,
China Railway Tunnel Bureau has organized technical teams to go deep into the site for many times to investigate the geological factors and surrounding rock conditions, and held a scientific and technological conference on the construction of soft rock tunnels with large deformation in plateau alpine highland stress. Through more than 50 times of demonstration and practice, the
anchor cable construction
builders and experts and academicians finally formed a new type of soft rock tunnel large deformation control technology and method, that is, through the mesh anchor cable system, the loose and fragile rock mass is compacted to form an arch bearing structure, which improves the stability of the rock mass. The anchor cable driven into the rock mass, like the sole of the shoe, strings up the carbonaceous slate and compacts it, which has the effect of reinforcement. At the same time, it disperses the extremely high horizontal pressure and vertical pressure into the rock mass, and then resists the later deformation through the single-layer arch to achieve a successful support, which reduces the maximum deformation on one side of the tunnel from 2 meters to 30 centimeters. In the construction
of Muzhailing extra-long tunnel, the scientific research team of China Railway Tunnel Bureau has obtained many invention patents, such as the method and system of surrounding rock support based on the theory of tunnel field solution reconstruction, and the equipment of small aperture and deep hole formation in soft rock. At present, this series of research results have been popularized and applied in more than 10 tunnel projects in China. After Muzhailing
Tunnel is opened to traffic, it only takes less than 12 minutes to cross Muzhailing, which still takes one hour to pass, and the passing vehicles do not need to go through the long downhill of 212 National Highway for 13 kilometers, so the driving efficiency will be greatly improved. Driving safety will also be guaranteed. After the opening
of Muzhailing Extra-long Tunnel through
Weiwu Expressway, the travel time between Weiyuan and Wudu will be shortened from 4 hours to 2 and a half hours, and the G75 Lanzhou-Haikou National Expressway, one of the north-south trunk lines of China's expressway network, will also be opened to traffic. It is of great significance to greatly improve the regional traffic conditions and investment environment, promote the development of mineral and tourism resources along the line, promote the economic development along the line, and promote the transformation of regional resource advantages into economic advantages. In the
future, Minxian and Zhangxian will be rich in 238 kinds of traditional Chinese medicines, such as Angelica sinensis, Astragalus membranaceus and Codonopsis pilosula, and mineral resources such as gold, antimony and petroleum can be transported to all parts of the country more quickly. More tourists can enter such tourist attractions as Sunshade Mountain, Guiqing Mountain, Langdu Wetland Grassland, Minzhou Conference Memorial Hall and Red Army Salt Well Memorial Hall, which will truly benefit the production and life of the people along the highway and promote sustainable economic and social development.
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