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Nantong Binjiang Area GIL Utility Tunnel Project

The GIL utility tunnel project in Nantong’s Binjiang District is part of the district’s infrastructure‑supporting development program. With a total length of 5.3 kilometers and a total investment of RMB 550 million, the tunnel system is situated along the north side of Yanhe Road and the west side of Changjiang Middle Road, and is being implemented by Nantong Transmission & Transformation Engineering Co., Ltd., a subsidiary of Nantong Power Supply Company. The project reconfigures four existing 220 kV high‑voltage power lines within the Binjiang District from overhead lines to an underground tunnel network, thereby providing a reliable foundation for the district’s long‑term planning and development. The project employs the latest GIL (Gas‑Insulated Metal‑Enclosed Transmission Line) technology, making it the longest such tunnel system in China at this voltage level. The total tunnel length spans approximately 30 kilometers, with individual sections ranging from a maximum of 2.7 kilometers to a minimum of 2.1 kilometers. As an underground tunnel structure, the design accommodates the local topography: the tunnel does not run straight throughout but features numerous bends and gradients. For special terrain features such as rivers, a pipe‑jacking technique is used to lower the tunnel beneath, with each jacked segment measuring about 240 meters and a maximum slope of roughly 10 degrees. In areas with complex geological conditions, large‑angle compensation units are installed, and the project incorporates more than 130 horizontal and vertical alignment changes. Additionally, nearly 1,000 corrugated pipes have been deployed throughout the system.
 

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