On August 28, at the No. 2 shield shaft in Yuehu Park, Changsha, a China Railway Sunward "mini" shield machine was officially launched, tunneling southward. This marks the official start of the 220KV power tunnel project on Wanjiali Road in Changsha—Hunan Province's first power shield tunnel project. It is understood that previous power tunnels were constructed using open-cut shallow burial methods, but the Wanjiali Road power tunnel is the first in Changsha to adopt shield tunneling. Shield tunneling not only offers fast construction speed and more controllable quality and safety, but also does not affect ground traffic or the lives of residents along the route.
As the first small-diameter shield tunnel in Hunan Province, the Wanjiali Road power tunnel faces multiple technical challenges such as narrow shaft space and low muck removal efficiency. To address these, the Changsha Public Works Bureau organized China Construction Fifth Engineering Division and China Railway Sunward to communicate repeatedly and optimize multiple times, creating a custom small-sized and special-shaped shield machine tailored to the project's characteristics. It adopts a single-side layout different from large shields, arranging dozens of types of equipment within limited space. The China Railway No. 13 shield machine launched this time was custom-built by China Railway Sunward for this project. The shield segment inner diameter is 3.6 meters, and the excavation diameter is 4.35 meters, only half the size of a subway shield, hence it can be called a "mini" shield machine.
The shield machine is 118 meters long, but the launch shaft is only 29 meters long, so the shield machine needs to be launched in sections by extending pipelines. During this process, the entire shield machine will be divided into 17 sections. The cutterhead and main unit will go down the shaft first for tunneling, while the rest of the parts cooperate on the surface. As the cutterhead and main unit advance, the rear shield tail sections will be lowered section by section, and eventually the shield machine will be assembled into a whole underground in about 35 days.
The China Railway No. 13 shield machine will tunnel southward from the No. 2 shield shaft and will be dismantled and lifted out upon reaching the No. 3 shield shaft. The total length is 2,859.95 meters, and breakthrough is expected in September 2019. China Railway Sunward was established in 2016 and focuses on the manufacturing and construction of underground engineering equipment. To solve key technical and complete equipment issues in underground engineering construction, it provides comprehensive solutions. In just over two years since its establishment, China Railway Sunward has produced a total of 18 shield machines for national rail transit construction. As a comprehensive underground engineering service provider, China Railway Sunward not only shines in subway construction but also can provide complete solutions for underground space construction such as municipal utility tunnels.