China: Qinghai-Xizang Railway Marks 20 Years of High-Altitude Operations - Get updated on what's happening in tourism!

Twenty years after trains began running to Lhasa, the Qinghai-Xizang Railway has become both a major transport link and an unusual laboratory for railway engineering. Crossing the world’s highest plateau, the 1,956-kilometre line connects Xining in Qinghai province with Lhasa in the Xizang autonomous region.

Since its inauguration, the railway has handled 104 million passenger journeys and more than 824 million tonnes of freight. Its most technically challenging section runs for 1,142 kilometres between Golmud and Lhasa and opened on 1 July 2006. With an average elevation of 4,440 metres, it exposes trains, tracks and electronic systems to low oxygen levels, extreme temperatures and extensive areas of permafrost.

Two decades of operation have therefore depended on engineering solutions developed specifically for one of the harshest railway environments in the world.

51 stations operate without on-site staff

Of the 58 stations between Golmud and Lhasa, 51 are remotely controlled and unattended. Digital train control has played a central role in allowing the railway to operate across vast, sparsely populated areas of the plateau.

The original system relied on satellite positioning, allowing trains to be tracked even where conventional ground signals were impractical.

“Wherever the train goes, you can see it from the sky,” says Zhang Huxiong, head of safety and quality inspection at the Golmud Electric Depot of the Qinghai-Xizang Railway.

China subsequently adapted a domestically developed train monitoring system to the demanding plateau environment. Electrical components were modified to withstand severe cold and low-oxygen conditions, while work focused on increasing reliability and reducing maintenance requirements.

The plateau-adapted system is now in operation on the Golmud-Lhasa section and can be maintained using domestic technology and expertise.

550 kilometres of permafrost present an engineering challenge

Keeping trains moving is only part of the challenge. Around 550 kilometres of the railway cross core permafrost areas, where changes in ground temperature can destabilise the track bed.

“The success of the Qinghai-Xizang Railway lies in the subgrade, and the success of the subgrade lies in the permafrost,” says Li Yongqiang, chief engineer of the Northwest Research Institute of China Railway Group.

Research into the problem began decades before the railway opened. China established its first permafrost observation station on the northern slope of Fenghuoshan Mountain in 1961. Located at an elevation of 4,750 metres, the station remains operational today.

The research eventually produced one of the railway’s most distinctive engineering features: rows of metal thermosiphons installed alongside the tracks.

Thermosiphons keep frozen ground stable

The sealed pipes contain liquid ammonia and use natural temperature differences to remove heat from the ground without requiring an external energy supply.

During warmer periods, the liquid absorbs heat and vaporises. The vapour rises through the pipe before condensing as temperatures fall, transferring heat away from the permafrost. The process helps prevent thawing beneath the railway embankment and the resulting deformation of the track.

The technology has been protecting the route throughout its first two decades of operation, but rising temperatures are creating new challenges.

The original engineering assumptions allowed for an increase in temperature of approximately 1.5°C over 50 years. More recent projections indicate that the increase could reach 2°C.

Solar-powered system increases cooling capacity

Researchers have responded by developing a new generation of solar-powered thermosiphons. The technology makes use of the plateau’s intense solar radiation and large differences between daytime and nighttime temperatures.

According to the researchers, the new system provides 1.5 times the cooling capacity of conventional thermosiphons. It has already been deployed across 117 permafrost sections of the Qinghai-Xizang Railway and has reduced settlement by more than 70%.

Monitoring over the past 20 years shows that 96% of subgrade settlement in permafrost sections has remained within 20 millimetres. The railway was designed for a maximum settlement of 50 millimetres.

Trains maintain 100 km/h across the plateau

The stability of the infrastructure allows trains to operate at speeds of up to 100 km/h on the high-altitude permafrost railway. According to the report, this is the highest operating speed achieved by a railway under comparable high-altitude permafrost conditions.

While the numbers underline the railway’s transport role, its first 20 years also illustrate the scale of the engineering challenge behind the route. Remote digital control, decades of permafrost research and increasingly sophisticated cooling systems have allowed regular train services to continue across a landscape where altitude, cold and a changing climate constantly test the infrastructure.

Image Credit: © AI generated illustration with material courtesy of Science and Technology Daily