The construction of a 15.2-km tunnel on the Kunming-Vientiane Railway to link China with Laos was completed on Sunday.

The Ganzhuang tunnel, located in Yuanjiang County in the city of Yuxi, southwest China's Yunnan Province, was the first high-risk tunnel with a length of more than 15 km to be built along the railway line, according to the China Railway Kunming Group Co., Ltd.

The tunnel goes through eight geological faults with complicated geological conditions, such as the deformation of soft rocks and noxious gasses.

Construction of the tunnel started in 2016 and 16 operation platforms were created to build it. An S-shape design was adopted to reduce the slope, said Zhang Jianfeng, a project manager with the China Railway 17th Bureau Group Co. Ltd.

The railway line is expected to be operational by the end of 2021.