Global warming may prove to be another problem for designers and
builders of the Qinghai-Tibet Railway under construction in
northwest China.
Already racking their brains for a solution to building the world's
highest railway on the permafrost earth, scientists are finding it
much harder than expected to find solutions to construction
problems exacerbated by the warming climate.
Many scientists and research institutions were working hard to
minimize the impact of global warming on the Qinghai-Tibet
Railway,said Lu Chunfang, leader of the construction project.
The frozen earth of the Qinghai-Tibet Plateau was degenerating
because of global warming and the increase in human activities in
the region, according to recent research.
Research produced by the Chinese Academy of Sciences indicated that
the perennial frozen earth on the plateau is now five to seven
meters thinner than 20 years ago, while about 10 percent of the
plateau's frozen earth had vanished.
Meteorological statistics show the annual average temperature on
the Qinghai-Tibet plateau has gone up 0.2 - 0.4 degrees Celsiusfrom
the 1970s to the 1990s.
Scientists said the climate changes had impacted on the ground
temperature to a depth of 40 meters, with greater changes in layers
to a depth of 20 meters.
Global warming had accelerated the erosion of the frozen earth,
exerting great pressure on the construction of the Qinghai-Tibet
Railway and its future operation.
Scientists said the success of the construction, and maintenance of
the railway, would be dependent on finding ways to stabilize the
gradually thawing earth.
The permafrost layer thickens as the temperature drops and thins
when temperatures increase, reducing the stability of the railway
foundation.
Scientists warned that fluctuations in stability caused by changes
in the thickness of the permafrost layer could create future
hazards if the problem was not resolved.
"We have taken the impact of global warming into consideration when
plotting the route of the railway," said Lu Chunfang.
When scientists began designing the railway, they predicted the
temperature on the Qinghai-Tibet Railway would rise only 1 degree
Celsius in the next 50 years.
But other scientists have estimated that the plateau temperature
may rise by 2.2 - 2.6 degrees Celsius in the next 50 years,
bringing greater pressure to bear on the design and construction of
the railway.
Construction bosses have adopted three special measures to ensure
the stability of the roadbed in the permafrost areas, including
changing routes, building railway bridges along sections of complex
geological conditions, and building soil layers that can insulate
the ground from heat created by the railway.
About 550-km section of the railway will traverse perennially
frozen areas, the longest stretch of its kind in the world.
The 1,956-km Qinghai-Tibet railway will run from Xining,the capital
of northwest China's Qinghai Province, to Lhasa, the capital of
Tibet Autonomous Region.
The section linking Xining and Golmud City in Qinghai was completed
in 1984. Construction of the 1,118-km section connecting Golmud
with Lhasa began in June 2001 and is expected to be completed by
2007.
The construction plan calls for a total investment of 16 billion
yuan (US$1.9 billion) for the 554-km permafrost section of the
railway.
(Xinhua News Agnecy April 30, 2003)