Dazhushan tunnel (Screenshot/CCTV) 

The 14.5-kilometer Dazhushan tunnel, linking Dali in southwest China’s Yunnan province by rail with Ruili, a city on the border with Myanmar, has been under construction for 11 years, with a further two kilometers to go before completion.

The complicated conditions have hampered progress, making the tunnel China’s most challenging tunnel project to date.

The geological and hydrogeological conditions around Dazhushan are complicated, and workers have faced many difficulties in terms of ventilation, transport and water in the process of building the tunnel.

Dazhushan tunnel (Screenshot/CCTV)

Jiang Dong, a project manager with China Railway First Group, the company behind the new line, said new troubles emerged every day, such as floor water inrush. Over the last 3,862 days since Jiang first got involved in the project, he has been fighting with water inrush and mudstones almost every day, as the tunnel runs through six fault zones.

When water inrush begins, the water can fill a standard swimming pool in approximately four hours. About 200 million cubic meters of water have gushed into the tunnel, and 116 suction pumps have helped to drain the water out.

More than 150 people were involved in the project at one time, but now only 36 people remain on the project, able to face the challenges both physically and mentally. Jiang said he would work until the tunnel is opened.