Tuesday, June 30, 2009

Secret of Ancient Village Surviving Earthquake

08/10/29 Taoping Ancient Qiang Village: The Secret of Surviving the Wenchuan Earthquake
Just like the Wenchuan Earthquake that struck southwestern China, earthquakes above a magnitude of 8 have brought destruction, pain and suffering to people in many parts of the world. Wherever they strike, they bring mass casualties and enormous loss of property.
The tragic scenes reflect the almighty and intimidating power of nature. Nature, like a powerful monster can, with a slight wave of an arm, cause high-rise buildings made of reinforced concrete to collapse like toy bricks.
So a humble village that has stood up to this monster could be considered an architectural miracle. Such a village exists. Its called Taoping ancient Qiang Village, and it is found in Li County, Sichuan Province.
Records reveal that the ancient Qiang village has faced three major earthquakes since the beginning of the 20th century; the magnitude 7.5 Diexi earthquake in 1933, the magnitude 7.2 Songpan-Pingwu earthquake in 1976, and the magnitude 8.0 Wenchuan earthquake on May the 12th, 2008. In the Wenchuan earthquake, while Taoping survived, all the other villages in the area were reduced to rubble.
Taoping ancient Qiang Village lies just 20 kilometres away from the epicenter of the Wenchuan earthquake. Yu Xingmei, a member of the Qiang ethnic group, still remembers the scene clearly.
Yet the only damage suffered by the village was to the parapet wall on top of the ancient watch tower. Its collapse was due to the architectonic phenomenon known as the whipping effect, in which the part nearest to the top of a building is most likely to be destroyed during an earthquake. However, the main body of the village, and even the 2-meter-wide lanes and the underground water network, survived intact. Not one of the Qiang houses and watch towers collapsed.
The first sight visitors get of Taoping Village is of three ancient Qiang watch towers standing abreast. Against the light, the three towers look like three pillars rising up to the sky. They, like the ancient and delicate Qiang houses that surround them, withstood the onslaught of the earthquake.
So, how exactly did the ancient village survive the great earthquake? And can the architects of today learn anything from the secrets of the ancient Qiang builders?
China is a country of many nationalities. In the great Chinese family, the Qiang people are one of the most ancient nationalities. Oracle bone inscriptions from 3,000 years ago record that the Qiang people were living mainly in Northwest China and the Central Plains. Later, a branch of the nationality was incorporated into the Tibetan ethnic group, and another into the Han Nationality. The Qiang people today are the descendants of the ancient Qiang Nationality. Theirs was a turbulent history, before they finally settled in the area of the Minjiang River and Minshan Mountain.
The earliest Taoping Qiang Village was built over 2,000 years ago, in 111 B.C.
Taoping is a typical Qiang village, in that it was built with mountains to the north and facing water to the south. The buildings are laid out according to a rigid design. Built of stone, they embody a structural hierarchy. The houses are called Zhuang Houses, or Wo Zhe in the Qiang language.
The ancient Qiang village has eight gates radiating from the watch tower. The eight gates are linked to 13 alleys, which form a comprehensive communications network. The village also has a network of groundwater, which uses covered wells. People can remove the slate covers to draw water from the wells. The alleys, groundwater network and roofs combine to form a comprehensive defence system.
After surviving the wind, rain and earthquakes for the past 2,000 years, Taoping ancient Qiang Village still stands proud. It is known as a wonder in the history of architecture. Its also known as the Mysterious Fortress of the East and the most intact Living Fossil of ancient Qiang architecture.
In surviving the earthquake, Taoping Village is indebted to its unique landform and topography.
If seismic waves move along a mountain range, which part of the mountain, the top, the valley or the mountainside, can best withstand the force?
Interestingly, in the Qiang village, some of the buildings are situated on the mountain top and some on the mountainside. But none are built in the valley. So, why did the Qiang people ignore the broad and even valley with its abundant arable land?

The first reason was, the difficulty in defending the valley. However, they gradually discovered there were other advantages associated with their choice, and the tradition developed among the ancient Qiang people of living in stone houses located beside mountains. Traditional Qiang villages were often built on a steep mountainside or at the mountains top, instead of on the flood plains beside a river. Because of this, the Qiang Nationality were popularly known as the people above the clouds.
Taoping ancient Qiang Village is located on a mountainside. The Zagunao River, the main tributary of the Minjiang, runs eastward across the village. Thanks to its location, the village is protected from the northerly wind in the winter and receives adequate sunshine. More importantly, the broad and gentle terraces mitigate the effects of the major earthquakes that strike the area once every few decades.
When seismic waves move forward along the mountain range, the valley and the mountain top receive the impact first. The valley, with its broad expanse of soft and flat land, absorbs the force of the earthquake and deadens its power, which significantly reduces the impact on the mountainside.
Even buildings made of reinforced concrete collapsed during the earthquake. So, was there something miraculous about the construction materials used in the Taoping ancient Qiang Village?
The Qiang people, like other ancient nationalities, knew how to take advantage of nature to satisfy their need to survive. The two mountains beside the village are a source of common but nevertheless priceless, construction materials.
One mountain has abundant rubble, of a kind grey, broad and thin that is highly durable. Used in construction, it is capable of altering its shape in accordance with changes in the forces it is subjected to, which serves to make the building more stable.
The other mountain is abundant in loess. The miraculous village was built of rubble mixed with loess and mud.
67-year-old Wang Jiajun is the only person in the village with a university degree. Hes a skilled architect, and also an expert on the construction theories of the Qiang village and watch tower.
Potassium nitrate is commonly referred to as niter or saltpeter. Niter varies, according to the amount of potassium nitrate it contains, but the proportion is usually less than 10%. So the loess in Taoping Qiang Village, which contains 20% potassium nitrate, is very rare. Its used in construction because of its outstanding ability to resist light, heat and corrosion.
Good nitre, if placed on burning charcoal, will sparkle.
Wang Jiajun picks up a handful of nitre from the wall and lights it with burning ash. The niter really sparkles.
The experiment shows how rich in potassium nitrate the rubble and loess here are.
Potassium nitrate is high-tensile and a powerful coagulant. Its use as a building material has been a key factor in the Taoping ancient Qiang Villages survival of 2,000 years of earthquakes.
So Qiang people use the locally-available rubble and loess as their construction materials.
Qiang people long ago became experienced in mitigating the effects of earthquakes. The techniques they developed are an intangible cultural heritage, which they incorporated into the construction of the ancient village.
Construction starts with digging the foundation, which can be square, hexagonal or octagonal, and must be three or four meters deep. The foundation must stand on bare rock. The foundation stones are large pieces of rubble.
In the wall, the pieces of rubble fit one another naturally. Evidently, there is nothing random abut this arrangement.
The builders first select good quality rubble and hammer the irregular pieces to get rid of any fragments. They then put the various pieces into place, adjusting their positions constantly so as to maximize the cohesion between rubble and loess. The adjustment can be repeated anything up to fifty times.
Experienced engineers made precise calculations concerning the bases of the walls and the walls themselves. Every piece of rubble and every handful of loess was carefully placed, the first layer lengthways and the second, sideways, so as to maximize the cohesion. Both sides of the walls had to be properly arranged, centred on large stones in the middle.

To increase the shock resistance of the walls, the Qiang craftsmen made them all slightly concave. They also formed a corner on every wall, known as the wall stud or Qianlengzi in the Qiang language. Wall studs placed at the edge of the houses would bear the full force of any earthquake, and would allow the Qiang houses to withstand both transverse and vertical shocks.
It was the practice, after each storey of a building was completed, for nothing to be built on top for at least a year. The Qiang people did this to allow the rubble and loess to settle, and bond more strongly. A wall would be deemed sufficiently stable only if it could withstand the climate changes and rainstorms of a whole year, without losing any of its loess.
So it took three years to build a three-storey Qiang building and thirteen years to build a thirteen-storey one.
The rubble and loess walls, built over 2,000 years ago, may look delicate. But they are in fact extremely solid.
To improve their resistance to earthquakes, Qiang houses were built in a pyramid structure, characterized by a wide bottom and a narrow top. The walls in the bottom layer are 60 cm wide, and those in the top layer, 20 to 30 cm wide. The entire wall leans inwards, towards the middle.
In a five-storey building, there could be a horizontal difference exceeding 20 centimetres between the top and bottom walls. The walls, being solidly built and symmetrical, are capable of withstanding a force from any direction.
Besides the solid walls, Qiang buildings incorporate other, supplementary support. Three wooden pillars form a system that supports the floors and the roof.
Qiang buildings are usually quite low. Those used for living and working tend to have just three storeys. The inner structure adopts the space cutting technique combining stone walls and beams. The layers of wall are separated every zhang by beams, 20 centimetres in diameter with rafters above them.
A smooth groove was cut in the top of the wooden pillar on the first floor, and another in the corresponding part on the bottom of the wooden pillar for the second floor. The main beam would be inserted between them. Sometimes a supplementary beam might be added, parallel with the main beam. This was in a fact a primitive form of a bucket arch, which could disperse the pressure from the junction of the wooden pillars and beams so as to strengthen the beams.
The interweaving of the beams and stone walls, combined with the joining of the beams and wooden pillars, effectively reinforced the whole structure and increased its capacity to withstand shocks.
Seen from above, the ancient Qiang village is revealed as a collection of buildings all forming a complete architectural complex.
The various houses are linked to one another in an integrated whole. The buildings and alleys, by being connected, can better withstand earthquakes.
Compared with the interconnected ancient Qiang houses, later Qiang buildings are more independent, in order to accommodate tourists. However, being independent makes the buildings more vulnerable to earthquakes.
The ancient Qiang people acquired their architectural genius by studying Nature. Having migrated from far away, they have now been living in this place for many generations. To visit Taoping ancient Qiang Village is like traveling back through the long history of the Qiang people.
It was raining on July the 15th, 2008. The Qiang people, still getting over the shock and devastation of the Wenchuan earthquake, were gathering beside the village entrance, dressed in their finest.
What were they waiting for?
I hereby launch the project to save and protect the watchtowers and villages of the Qiang Nationality! With these words from Shan Jixiang, director of the State Administration of Cultural Heritage, the Qiang started to sing and dance, celebrating the preservation of their unique heritage.
Guided by such principles, the Qiang village is promised an even better appearance in the future.
Today Taoping ancient Qiang Village is much more than a remarkable collection of buildings. In a sense, the Qiang houses and watch towers have assumed a historical mission: to keep alive a unique architectural culture. Architecture in its highest form incorporates into buildings mankinds respect for life, and lays a solid foundation for the survival of human beings in their rapidly-changing environment.

(source: CCTV upload in youtube)

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