A pipe-jacking utility tunnel for Section III of Zhuhai's Diequan (Jinhai) Macao-bound 220-kilovolt power transmission and transformation project was broken through on Dec 3.

The Maliuzhou Waterway tunnel is a key node of the Jialin-Diequan power transmission line. The line will increase the capacity and reliability of power supply from the 500-kilovolt Jialin Station to Macao via Hengqin New Area.

The tunnel at the bottom of the waterway is 60 m (66 yd) from the Second Hengqin Bridge. China Railway Tunnel Group dug two working wells of 36 m (39 yd) and 29 m (32 yd) deep on both banks and pushed a prefabricated concrete tunnel with an outer diameter of 4.14 m (4.5-yd) into the riverbed through pipe-jacking technology.

The 619-m (677-yd) submarine cable tunnel stretches 485 m (530 yd) across the waterway. It is longer and deeper than those of the same inner diameter in the Guangdong power grid, according to an official of the Zhuhai Power Supply Bureau.

Working well near Second Hengqin Bridge [Photo by Chen Xinnian / Zhuhai Daily]