Nine Ming Mogao Grottoes in Lu Se

From June 5438 to October 2007, Gansu Bureau of Surveying and Mapping sent technicians to Dunhuang to monitor Mingsha Mountain on the west side of Mogao Grottoes. This is the second time that Gansu Provincial Bureau of Surveying and Mapping has participated in the protection of Mogao Grottoes since 1980s.

Twenty years ago, major newspapers all over the country published such a news one after another-Mingsha Mountain was advancing on the Mogao Grottoes at an average annual speed of 10 meter, and the Mogao Grottoes were in danger of being swallowed up by quicksand.

So, what kind of movement is Mingsha Mountain in? What's wrong with the murals and painted sculptures in Mogao Grottoes? What will happen to the fate of Mogao Grottoes?

The Mogao Grottoes are located 25 kilometers southeast of Dunhuang, facing Sanwei Mountain in the east, and the rocks are hard. One kilometer away from the west is Mingsha Mountain, which is formed by desert. The mountain is gentle and often has quicksand.

In 366 AD, Monk Youzun dug the first grotto here. After that, during 1600 years, a large-scale cave group gradually formed. At present, 735 caves, 45,000 square meters of murals and more than 2,000 statues have been found in the Mogao Grottoes, making it the largest Buddhist cave group in the world.

However, it is this Mogao grottoes with the reputation of "museum on the wall" that has left many protection problems for future generations.

Sandstorm is almost an innate disaster in Mogao Grottoes.

On the Gobi at the top of the Mogao grottoes, there are countless dunes; After Gobi is Mingsha Mountain, which stretches for forty or fifty kilometers and is more than ten meters high. The Mogao grottoes, located in the desert, have been attacked by sandstorms since they were dug. The ancients repeatedly looked at the sand and sighed, expressing their helplessness that "the Buddha statues were repeatedly destroyed and the shrines were buried in the sand".

It was not until 1944 that the National Dunhuang Art Research Institute was established that the problem of quicksand was taken seriously. However, due to limited financial resources, sand damage has not been effectively controlled.

According to the observation in the 1960s, the annual average wind speed in Mingsha Mountain is about 4 meters per second, with the west wind, northwest wind and southwest wind being the most in spring and autumn.

In order to control quicksand, Dunhuang cultural relics protection department has made many attempts. Since then, Dunhuang Research Institute has tried to plant drought-tolerant plants such as wild pepper on sand dunes in a small area to fix quicksand. Most caves have installed doors and windows one after another to prevent sandstorms from entering the caves; The ground in front of the cave is also paved with cement bricks, which have been cleaned by people for many years.

From 65438 to 0987, the Mogao Grottoes was listed as a world cultural heritage by UNESCO. Shortly thereafter, it was reported that Mingsha Mountain was advancing on the Mogao Grottoes at the rate of 10 meter per year, and the Mogao Grottoes would be swallowed up by Mingsha Mountain in the near future.

In 2002, Gansu Provincial Bureau of Surveying and Mapping officially intervened in the sand control work of Mogao Grottoes, and laid 24 permanent surveying markers around Mingsha Mountain. They were observed twice in a year to judge the movement of Mingsha Mountain by whether these markers moved or not. The movement of Mingsha Mountain is inseparable from the influence of the wind. After several years of monitoring, experts finally mastered the characteristics of various wind directions in Mingsha Mountain.

The Mogao grottoes are located in the hinterland of the desert, and the sand mainly comes from Mingsha Mountain on the west side of the grottoes. Among the winds coming from all directions in the Mogao Grottoes, there are mainly three groups of wind directions: south wind, west wind and east wind. When thousands of people blow through the vast sea of sand, the undulating sand leaves the shape of the wind.

Monitoring shows that the wind speed below 5 meters per second will not carry sand; A wind of 5 to 8 meters per second will cause ripples in the sand; Only when the wind speed reaches more than 8 meters per second will it have the bearing capacity for sand materials.

Although according to the monitoring of surveying and mapping experts, desert researchers gave an accurate judgment and analysis of the movement state of Mingsha Mountain, and drew a gratifying conclusion: Mogao Grottoes could not be annihilated by Mingsha Mountain.

After the 1980s, Dunhuang Research Institute adopted special nylon products with high density, high temperature and cold resistance, solar radiation resistance, wind resistance and wear resistance, and set up a type A nylon net fence with a length of 800 meters in the south and a length of 1.024 meters in the north, an included angle of 83 degrees and a net height of 1.8 meters, with the top pointing to Mingsha Mountain.

Because most of the murals and colored sculptures in the Mogao Grottoes are concentrated in the South Grottoes, which is about 1000 meters long, the included angle, side length and height of this A-shaped sand screen have been accurately calculated and designed, just to protect the South Grottoes in your arms.

The "A"-shaped nylon net fence not only blocks quicksand in the main wind direction, that is, the west wind direction, but also plays the role of transporting and guiding sand in the south wind direction and the east wind direction.

It is estimated that type A sand net blocks about 75% of quicksand every year.

At the same time, Dunhuang Research Institute also implemented the biological sand fixation plan.

Experiments show that a willow tree can intercept 15 cubic meters of quicksand in Gobi desert for one year.

Because the Mogao Grottoes are located in extremely arid areas, and the precipitation is scarce, Dunhuang Research Institute has set up a windbreak and sand-fixing shrub belt composed of five kinds of sand plants at the foot of Mingsha Mountain and the west side of the sand prevention net, relying on the drip irrigation technology imported from the United States.

Monitoring shows that only when the wind speed is greater than 1 1 m per second, Mingsha Mountain will transport huge sand sources. Not only Mingsha Mountain, but also local sand blowing from the Gobi section west of A-type sand control network will endanger the Mogao Grottoes.

Therefore, Dunhuang Research Institute uses local materials in Gobi area to crush gravel and sand. This can not only cover the sand source and fix the sand surface, but also reduce the roughness of the ground, making the Gobi area not conducive to sand accumulation.

So far, Dunhuang Research Institute has gradually established a comprehensive protection system combining various means, and the sand control project has achieved remarkable results.

Compared with the 1980s, the damage of sandstorm to Mogao grottoes has gradually decreased, and the sand accumulation in the grottoes has decreased by 90%. The accumulated sand swept out of the grottoes every year has also decreased from 3000 or even 4000 cubic meters in the last century to about 300 cubic meters now.

Monitoring Mingsha Mountain to prevent wind and fix sand ... A series of measures to protect Mogao Grottoes were implemented in an orderly manner.

However, the monitoring data of Mingsha Mountain by Gansu Bureau of Surveying and Mapping in June 5438+ 10, 2007 showed that compared with the monitoring results in 2002, this sand ridge line moved 5.8 meters from southwest to northeast on average in five years. Mingsha Mountain still threatens the Mogao Grottoes all the time, and the situation of sand control is still grim.

While controlling Mingsha Mountain, it is also an urgent task to protect the Mogao Grottoes by preventing and repairing mural diseases.

From June 5438 to October 2003 10, Dunhuang Research Institute and Gansu Bureau of Surveying and Mapping cooperated again to accurately measure the space and state of Mogao grottoes, as well as the location, area and diseases of murals, and established complete and reliable files for these murals to understand their dynamic changes and disease distribution.

At the same time, Gansu Provincial Bureau of Surveying and Mapping also used close-range photogrammetry technology to survey the cliff body of Mogao Grottoes and its surroundings, which provided detailed environmental information for Dunhuang Research Institute to control mural diseases.

The surveying and mapping work carried out by the Bureau of Surveying and Mapping of Gansu Province in 2003 not only provided detailed information on murals and their diseases, but also produced a large-scale topographic map of nearly three square kilometers around the Mogao Grottoes, obtained high-precision three-dimensional basic data of the cliffs of the Mogao Grottoes, and established a detailed and systematic cliff file, which provided a more reliable basis for Dunhuang Research Institute to better control the invasion of murals and natural disasters on the cliffs.

In fact, Dunhuang Research Institute has never stopped treating mural diseases since the founding of the People's Republic of China.

Among them, the most puzzling thing for experts is to find the root of mural diseases.

From 386 AD to today, the Mogao Grottoes have been eroded by wind erosion, weathering, dust, earthquake and rain. It should be said that the primary cause of mural disease is time.

Most of the caves in Mogao Grottoes are built on loose gravel hills, which also lays a hidden danger for mural diseases.

In recent years, Dunhuang Research Institute found that another main cause of mural diseases is water and salt through cave environment monitoring and mural color monitoring.

Although there is little precipitation in the Mogao Grottoes, there is a complex and tiny water system in the desert rocks. The unique hard water in the Mogao Grottoes permeates everywhere along the extremely narrow cracks, dissolving the soluble components in the rock layers and moving around. When water enters between the rock stratum and the wall, even inside the wall, the salt will dissolve, crystallize and accumulate repeatedly, which will destroy the structure of the mural in the long run and lead to many diseases such as nail peeling and hollowing.

The potential harm caused by more and more tourists entering caves can not be ignored. A large amount of carbon dioxide exhaled by tourists inadvertently aggravated the disease of murals. The official opening of the Mogao Grottoes began at 1979, and nearly 4 million tourists visited it successively. It is estimated that in the next five to 10 years, the number of tourists to the Mogao Grottoes will increase to more than 600,000 every year.

At the same time, Dunhuang Research Institute has gradually intervened in the increasing number of tourists, dividing 60 open caves into 12 tour routes and diverting tourists every day.

To prevent the deterioration of mural diseases step by step, mural restoration is a protracted and huge project.

Since 1950s, mural restoration has lasted for more than half a century.

A series of repair work is not only the most delicate operation, but also the highest art. Dust removal; Inject latex; Exhaust air; Rolling surface. A wrong hand and a wrong eye will bring irreparable losses. Over the years, * * * has more than 3,000 square meters of endangered murals and 100 colorful sculptures coming back to life here.

It is very important to cultivate feelings when repairing murals. It usually takes 5 to 10 years of on-site operation experience to cultivate the sense of touch, and an assistant can start the simple restoration of murals at least 5 years later.

At present, Dunhuang Research Institute has seven mural restoration teams with the largest number and the most sophisticated technology in China.

The Mogao Grottoes are accumulating experience for the protection of cultural relics in China and the world-the Qizil Grottoes in Xinjiang, the Potala Palace in Tibet and even the ruins of Guge Kingdom in Ali are all learning from the experience of the restoration of murals in Mogao Grottoes.

In addition to intensive restoration of murals, Dunhuang Research Institute also used digital technology in mural protection. Since 2005, Dunhuang Research Institute has completed the 3D animation roaming of 40 caves.

Wandering in the cave can not only avoid the potential harm of colored plastic murals, but also keep a beautiful electronic file for this art treasure house.

The Mogao Grottoes belong to China and the world.

Today, the remains of ancient civilization are colliding with modern civilization, and people have lost too many memories from their ancestors. It is still a long way to go to manage Mingsha Mountain and let Mogao Grottoes seek eternal life in the sand sea. The restoration and protection of the murals in the Mogao Grottoes is a great civilization rescue that China and even the whole mankind can't afford to lose.