"There is ice," shouts one of the team members Li Yubin.

And with a flashlight in his hand, he moves cautiously.

Due to the slippery gravel along the track it is so difficult to walk and he can move only on railroad crossties.

But the team is unfazed. Thanks to months spent walking on the evenly arranged crossties, they can move with their eyes closed.

The workers carry ladders on their shoulders and move so quickly that an operation can take less than half an hour, leaving only a pile of residual ice below the ladders.

The ice-breaking on the cave walls has become more frequent and important since the electrification of the railway in the early 1980s.

Although tunnel cracks are filled with anti-penetrating agents each summer, the ice-breaking work is necessary.

The work is monotonous but dangerous as well.