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Modern Technology Ensures Preservation of Dunhuang Grottoes
The 735 caves of the world-famous Mogao Grottoes in Dunhuang, west China's Gansu Province, remain safe and sound after severe floods pounded them last Saturday, only two days after the 100th anniversary of the discovery of the "Sutras Cave."
Wang Wanfu, deputy director of the Conservation Institute of the Dunhuang Research Academy, a center of Dunhuang studies, said that the flooding was caused by heavy rain which poured into the dry channel of the Daquan River in front of the Mogao Grotto Cliff.
"The one meter high flood destroyed a major bridge nearby," Wang said, but the Mogao Grottoes stayed intact thanks to the effective protection system in place at the relic site.
Governments at all levels have invested more than 100 million yuan (12 million U.S. dollars) to protect the Mogao Grottoes since the founding of new China in 1949.
Chinese scientists have been successful in protecting the world- class heritage relics from being damaged by natural disasters.
Located at the west end of the Hexi Corridor in Gansu Province, Dunhuang was once an important cultural and trade city along the Silk Road linking Central Asia with China.
Dunhuang attracts visitors mainly because it contains some of the most priceless examples of Buddhist art in the world: the Mogao Caves, which were carved out of the rocks, stretching for about 1,600 meters along the eastern side of the Sanwei Hill, 25 km southeast of Dunhuang.
The caves have preserved numerous frescos dating back to eleven dynasties from the 4th to 14th centuries and covering an area of 45,000 square meters. They contain more than 2,000 colored sculptured figures and five wooden eaves hanging over the entrance of the caves.
Archaeologists said the caves are the greatest and most consummate repository of Buddhist art in the world. Li Zuixiong, vice-president of the Dunhuang Research Academy, said that Chinese archaeologists are trying to adopt all possible protective measures and advanced technology to protect the site, including desert control, cliff reinforcement, sculpture preservation, and fresco repair.
At the same time, they have developed a series of high-tech methods including the computerized fresco repair, computer- simulated caves and database information, Li said, adding that these techniques will help reproduce lifelike Dunhuang art for posterity.
Before the founding of new China, many caves in the grottoes were tumble-down and vulnerable to natural and man-made damage. Since 1950, the Chinese central government has launched a range of repair projects on the 1,600-year-old site, which was put on the World Heritage List by the United Nations Educational, Scientific and Cultural Organization in 1987.
First, the sand dunes that had collected in front of the grottoes were cleared away, then the hillside grottoes were harnessed with reinforcing steel and limestone bars. Many wooden footbridges were also built to link the caves and tighten the stability of the grotto hill.
In the past half century, no reports on grotto collapse or landslide have come from the site.
"We also use the chemical grouting technology to control rock cracking," he said. As a result, the Mogao Grottoes can survive an earthquake measuring up to seven on the Richter scale, Li noted.
Mogao Grottoes have long been threatened by shifting sands from Mingsha Hill, which is only 1,500 meters from the caves.
The Dunhuang Research Academy and the Getty Conservation Institute of the United States jointly conducted a three-phase project to stop the sand from reaching the caves.
The first step was to grow some desert plants at the foot of Mingsha Hill to keep the sand in place. Nylon fencing was erected around the caves in the second phase.
The final weapon used to curb soil erosion and drifting sand was silicon emulsion, which was sprayed to fix the sandy surface onto the top of the caves, Li explained.
So far, the project has helped reduce the annual amount of sand invading the cave area by 70 percent, he said.
To repair grotto frescoes plagued by mold, fading and cracks, Chinese archaeologists and foreign experts have used high- precision equipment to analyze fresco paint and sculpture structure.
Using art preservation techniques, the experts have repaired over 3,000 square meters of damaged frescoes, Li said. Moreover, Chinese archaeologists are researching computer data to reveal the original color and appearance of the Dunhuang frescoes.
"Through computer-simulated caves, people can experience a lifelike scene from one thousand years ago," he said.
Detailed information about the grottoes will be stored in computers so that future generations all over the world can have the chance to enjoy the wonderful frescos from ancient times, he said.
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