NANNING, Feb. 13 (Xinhua) -- A group of railway workers in south China's Guangxi Zhuang Autonomous Region have successfully cleared loose rocks above a rail tunnel, which posed a major threat to trains ahead of the Spring Festival travel rush.

The team of 18 railway workers took more than three months to secure an area of lose rocks above a railway tunnel in Yongfu County, using concrete and iron bars.

The railway line links Liuzhou in Guangxi with Hengyang in Hunan Province. About 140 trains run on the busy line per day.

Karst mountains are common in Guangxi. About 80 percent of railways in in the region run through mountainous areas. Weathering easily leads to falling rocks, thus posing a threat to passing trains.

"In a safety patrol, technicians found the number of loose rocks had increased due to weathering above the Shawan Tunnel," said Lan Yong from China Railway Nanning Group.

High-speed trains had to slow down from 200 kph to below 80 kph when passing the area due to the loose rocks.

"The safety of the rail line is what everyone cares about most. A small rock on a mountain can become a time bomb," said Lan.

In mid-October, the team began their work on the 3,000-square-meter area on a steep hill at a height of 200 meters.

"It was very difficult," said Lan. "When we chopped down trees on the cliff, we had to prevent the branches and debris from falling onto the rails while ensuring our own safety."

The work was completed at the end of January, just a few days before the Spring Festival travel rush which began on Feb. 1 and will end on March 12. About 3 billion trips are estimated to be made nationwide during the period. High-speed trains have now returned to their normal speed of 200 kph when passing the area.