Two travel guides from the train's destination Gansu province introduce the scenic spots in the Northwestern Chinese province on the bullet train D2685, July 9, 2017. [Photo/Xinhua]

Building a high-speed railway along the Loess Plateau was not an easy task. The new line runs through the erodible soil of the plateau, with more than 90 percent of the tracks being built on bridges or in tunnels.

"Building a high-speed railway here is like building a high-speed railway on tofu," said Yuan Tao, project manager of the Gansu section of the Baoji-Lanzhou high-speed rail project from the China Railway Construction Corp.

Zhu Yaozhang, chief engineer of the Gansu section, said, "It was a big challenge to build a high-speed railway on the Loess Plateau due to the complicated geological environment.

"The erodible soil is fragile, and can subside when saturated," Zhu said, adding that such soil can cause geological hazards such as landslides.

Because the soil is prone to subsidence, a simultaneous observation system has been built to closely monitor the state of the soil.

"The system collects data, which is monitored by technicians to prevent damage and ensure safety," he said.