Recently, a press briefing was held for the Wanjiali Road 220KV Power Tunnel Project. As Hunan's first power shield tunnel, the Wanjiali Road 220KV Power Tunnel is tasked with supplying power to the intercity railway, Metro Line 3, and Metro Line 5. Once completed, the power tunnel will create a spacious underground "home" for high-voltage cables, and all overhead "spider webs" along Wanjiali Road will disappear. Currently, the project has been fenced off and organized for implementation, with a contract period of 2 years.

The project contractor, China Construction Fifth Engineering Division Corp., Ltd. Civil Engineering Branch, through public bidding,层层考核、调研及技术交流, finally determined to use two 4100mm shield machines produced by China Railway Sunward Engineering Equipment Co., Ltd. for shield construction.

This is another beneficiary project following the Wanjiali Elevated Road project, bringing convenience to citizens, and it is also a project with extremely high construction requirements. Previous power tunnels were constructed using shallow cut-and-cover methods, but the Wanjiali Road Power Tunnel is the first in Changsha to adopt the shield method. Shield construction not only speeds up construction and makes quality and safety more controllable but also does not affect ground traffic or the lives of residents along the route.

As the biggest construction challenge of the entire line, the Wanjiali Road 220KV Power Tunnel needs to pass under the Sanyi Avenue Interchange. To ensure bridge safety, it can only cross Sanyi Avenue in a sharp curve at a location with sparse bridge piles, with a minimum turning radius of 150 meters, and continuously pass through four small curves near the elevated bridge piles around Sanyi Avenue. At the same time, it must also pass beneath the Metro Line 3 tunnel and 12 station entrances/exits of Metro Lines 3 and 5, and under the known karst cave area of the Liuyang River, all of which bring great difficulty to construction.

The first shield is scheduled to be lowered into the shaft on June 15 of the same year. Due to space and site constraints (the tunnel has an inner diameter of 3.6 meters and an outer diameter of 4.1 meters, making it a small cross-section shield tunnel, about half the size of a subway tunnel cross-section), the shield machine can only be launched by split launching, which is more difficult in early organization compared to other large shield projects. As excavation distance increases, the advance rate and muck transport rate cannot be proportional. Based on the most ideal excavation calculation, the average daily advance is expected to be 7-8 meters.

The shield machine manufactured by China Railway Sunward for this project has a total length of 110 meters, while the minimum turning radius is only 150 meters, which places very high demands on construction techniques. Currently, the project department has cooperated with Central South University to conduct model analysis on "Research on Disturbance Effects and Control Methods of Shield Tunneling under Sensitive Buildings in Water-Rich Sandy Gravel Strata for Power Tunnels" and "Research on Attitude Control and Muck Conditioning of Shield Machines Crossing Composite Strata in Continuous 150m Small-Radius Curve Sections," which will solve the challenges existing in the power tunnel project.

As a comprehensive underground engineering service provider, China Railway Sunward not only excels in subway construction but also offers complete solutions for municipal utility tunnels and other underground space projects.