Construction of China's first high-speed railway running through the country's southwest karst region was completed on Sunday.

The 857-kilometer railway linking Guiyang, capital of Southwest China's Guizhou Province, with Guangzhou, capital of South China's Guangdong Province, is expected to become operational on Friday.

Stretching through the complicated karst clusters, the railway has half of its length running through 238 tunnels, two of which are more than 14 kilometers long, said Zhang Jianbo, general manager of Guiyang-Guangzhou High-Speed Railway Co.

It took builders four years to drill through the two longest tunnels. Construction was often disrupted by breaking rocks and water infiltration, Zhang said.

The construction firm applied for six national patents covering their shockproof technology which was adopted to reduce the vibration that occurs when a fast train traveling at 250 kilometer per hour runs through mountain tunnels.