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The world's first large-section horseshoe-shaped shield tunneling machine was officially started in the Baicheng Tunnel of the Menghua Railway of the Fourth Railway Bureau of Jingbian County, Yulin City, Shaanxi Province. This is the first time in the field of domestic railway mountain soft soil tunnels to use the horseshoe-shaped shield construction method to excavate tunnels. The history of tunnel construction technology and equipment development has a milestone.
The Baicheng Tunnel, built by the China Railway Fourth Bureau, has a total length of 3345 meters and is a single-hole two-line electrified railway tunnel with a speed of 120 kilometers per hour. The maximum depth is 81.05 meters. After many expert arguments, the tunnel was changed from the previous mining method construction to the special-shaped shield construction method. As the world's first large-section horseshoe-shaped shield machine, its length is 110 meters and its weight is 1,300 tons. Because the shield cutter has a "U" shape and looks like a horseshoe, it is named the horseshoe shield machine. The outer contour of the shield machine is 10.95 meters high and 11.9 meters wide. The shield body adopts a shuttle structure, which can effectively reduce the friction between the shield and the ground layer, thereby reducing the propulsion resistance. The cutter head is composed of 9 small cutters. The innovative combination of horseshoe-shaped sections is used for cutting and excavation, and is unearthed by a double-screw conveyor. The continuous belt conveyor transports the slag and the maximum tunneling speed is 60 mm/min.
Compared with the traditional circular shield machine, the shield machine can effectively reduce the excavation area by 10%-15% and maximize the utilization of tunnel space. At the same time, the Baicheng tunnel is located in the Mu Us Desert and the Loess Plateau in China. At the junction, it belongs to the soft soil soft rock geology, the soil is soft, the mining method is used, the construction efficiency is low, and the construction risk such as collapse collapse is easy. However, the horseshoe-shaped shield construction method avoids the risk of collapse collapse, and the construction efficiency is extremely high. Digging 200 to 300 meters per month can effectively reduce the construction period.