（单词翻译:单击）
A key stage in the construction of Gongbei tunnel, which will connect south China's Zhuhai city with Macau, has been completed. Pipe roofing has now been installed to reinforce the tunnel, in one of the largest construction projects in China.
The Gongbei tunnel is an important part of the Hong Kong-Zhuhai-Macau Bridge project. The 2.7-kilometer long tunnel passes under a customhouse in Gongbei in Guangdong province.
The pipe roofing uses dozens of steel pipes to form a huge outline of the tunnel. It was a very difficult process to install the pipes due to complicated geological conditions.
The construction of the Hong Kong-Zhuhai-Macau Bridge started in 2009. It will eventually span a length of nearly 50 kilometers, and will allow passengers to journey from Zhuhai to Hongkong in only half an hour when the bridge is completed.
