Chongqing - As heavy rains lashed the mountains of Chongqing recently, a group of railway maintenance workers clambered up steep cliffs, anchoring themselves with ropes and inspecting every crevice of the landscape—assisted not by luck, but by drones.

A drone lifts off to begin its aerial inspection of the mountainside. (Photo/Zhao Xin)

"Today, we're inspecting the Yangliucun and Houjiapo tunnels for loose rocks or other hazards. Stay sharp- every detail matters," said Yang Li, foreman of the Qianjiang High-Speed Railway Bridge and Track Workshop, Fuling Track Maintenance Section, China Railway Chengdu Group Co., Ltd, with 12 years of experience, rallying his team at dawn on June 24.

The inspection took place ahead of tomorrow's opening of the Chongqing East-Qianjiang section of the Chongqing-Xiamen High-Speed Railway (HSR). According to the Chongqing Meteorological Service, heavy rainfall is expected from June 24 to 26, with Qianjiang and Fengjie identified as high-risk areas for geological disasters.

The 269.5-kilometer rail segment, part of China's national "Eight Vertical and Eight Horizontal" high-speed rail grid, features a design speed of 350 km/h. Once operational, it will reduce travel time between Chongqing's urban core and Qianjiang District from four hours to under one. But the route's terrain poses a serious challenge—bridges and tunnels account for 93.88% of the section, cutting through rugged mountains blanketed in dense vegetation.

To mitigate these risks, the China Railway Chengdu Group has deployed a specialized drone patrol unit, pairing cutting-edge aerial surveillance with hands-on inspections. Their mission: examine 98 high-risk mountain slopes along the line for signs of instability.

At 7 a.m., the team hikes along a winding path to reach their first mountainside above the Yangliucun tunnel. Yang launches a drone fitted with a high-resolution zoom lens, guiding it like a hawk over the slope. The drone's feed reveals a suspicious crevice.

Workers climb rope-assisted routes to inspect areas beyond the reach of drones. (Photo/Zhao Xin)

"K218+631, possible rock movement inside the retaining mesh. Zheng Xiang, Xie Jianghong, go check it," Yang radios.

On the ground, workers climb 30 meters up the cliff using safety ropes. Dangling from rock faces, they secure a teetering stone with steel wire. Some zones are too dense for drone access, forcing crews to switch to traditional methods- scaling cliff after cliff, often for hours.

After three hours, the team completes its sweep of the first slope and marches toward the next inspection point. At Houjiapo, Yang leads the way again: "This slope eats shoes, feet, and pants—no trails, just rocks. I'll fix the rope first."

Workers mark unstable rocks with brush paint to flag potential hazards for further reinforcement. (Photo/Zhao Xin)

Thanks to the drone data, they've built a VR panoramic model and 3D maps of the entire line, enabling them to identify and respond to hazards far more efficiently. "Manually, we could only check two slopes a day. With drones, we can inspect several. That means more ground covered, faster," Yang explains.

By 2 p.m., the day's inspections are complete. The crew eats biscuits and bread on their walk back. "It's hard work- skipping meals, climbing cliffs- but knowing we helped this line open safely makes it all worth it."

On May 9, the Chongqing East-Qianjiang section of the Chongqing-Xiamen High-Speed Railway entered the trial operation phase, with a testing train departing from Chongqing East Station. (Photo/Cui Li)

Since construction began in May 2020, the Chongqing East to Qianjiang section of the Chongqing-Xiamen High-Speed Railway has progressed efficiently, overcoming complex geological challenges like karst formations. Using advanced techniques and standardized management, the project completed key infrastructure, including the Wulong Taiziping Wujiang Railway Bridge and Baima Mountain Tunnel, ensuring timely completion.

With the opening of the Chongqing East-Qianjiang High-Speed Railway (HSR) and the completion of the full line to Changsha, travel time between Chongqing and Changsha is now reduced to 3 hours and 53 minutes. This improvement enhances connectivity between the Chengdu-Chongqing Economic Circle and the Chang-Zhu-Tan city cluster, fueling regional economic growth.