Trucks pass through a road section of the Qinghai-Xizang Highway built on permafrost flanked by metal pipes, which serve as conductive heat pipes to stabilize the temperature of the permafrost layer, on the Qinghai-Xizang Plateau in northwest China's Qinghai Province, Dec. 2, 2024. (Xinhua/Jiang Fan)

On the Qinghai-Xizang Plateau in China, drivers jokingly refer to a section of a highway as the "washboard road" or "a road of potholes" because it undulates like waves and driving a little faster will cause severe car bumps.

The road section, located at an average altitude of more than 4,500 meters, was built on permafrost, making the road surface prone to distortion.

This year marks the 70th anniversary of the operation of the Qinghai-Xizang Highway. Dubbed the "Suez Canal on the roof of the world," the highway shoulders the responsibility of transporting 70 percent of the goods to Xizang Autonomous Region and 30 percent of personnel, with an average annual vehicle flow exceeding 1.3 million.

Of the highway's total length of over 1,900 km, 550 km are permafrost sections.

"Permafrost expands dramatically like ice freezing in winter, causing road surfaces to bulge, while in summer, it contracts rapidly like melting ice, leading to the sinking of the surfaces," said Chen Donggen, a scientist stationed in the city of Golmud, Qinghai Province, along the highway for permafrost research. "The undulations directly affect traffic safety."

To ensure the safe operation of the highway, Chinese scientists have been studying permafrost for many years.

By setting up observation stations on the plateau, they have collected a large amount of data on the changes in the permafrost layer.

The data shows that over the past few decades, the temperature of the permafrost layer on the Qinghai-Xizang Plateau has been gradually rising, and the melting pace is accelerating.

Chen Donggen (L), director of the Golmud observation and research base under CCCC First Highway Consultants Co., Ltd., a highway survey and design company, checks permafrost samples with a colleague in Golmud, northwest China's Qinghai Province, Dec. 3, 2024. (Xinhua/Jiang Fan)

To cope with the impact of the permafrost, a series of measures have been adopted.

A common practice is the application of metal pipes on both sides of the road sections, said Chen, also director of the Golmud observation and research base under a highway survey and design company. "The metal pipes serve as conductive heat pipes to stabilize the temperature of the permafrost layer," he said.

In addition, scientists have added "insulation boards" on top of the permafrost layer, using special materials to create boards that can prevent heat from transferring downward in summer.

"This is similar to how we used to see the elderly selling popsicles, wrapping them in thick blankets," said Chen.

Beneath the road surface, a row of ventilation ducts are buried above the roadbed. With the inside airflow carrying away the heat from the surrounding soil of the roadbed, the ventilation ducts help effectively maintain the low temperature of the roadbed and reduce the melting of permafrost, keeping the stability of the roadbed, Chen added.

Over the past 70 years, the Chinese government has invested heavily in multiple renovations and reconstructions of the highway, transforming from the original gravel road surface to the current asphalt surface.

In national nature reserves, construction workers have built viaducts to replace some road sections along the highway, with the latest one built in 2020.

Gao Yongli, Party chief of the development and emergency response center of the Qinghai-Xizang Highway, said viaducts not only improve the straightness of the road surface but also reduce the highway's impact on wildlife, allowing wild animals to migrate unaffected by the traffic.

"The less disturbance to the permafrost layer, the more beneficial it is for the stability of the highway's roadbed," he said.