The Study Of Seismic Stability Of The Rammed Great Wall In Hexi Area

The Great Wall is a great military defense project in ancient China,and it is also a great historical heritage of the Chinese nation to the world.The Great Wall of Han Dynasty and the Great Wall of Ming Dynasty were built in Hexi Area in Gansu province.The Han Great Wall and the Ming Great Wall are paralleled in some places,this scene is hard to see in other places of our country.But the Great Wall has been destroyed in Hexi area.Hexi region is earthquake-prone area,there are three seismic zones: The Altyn Tagh seismic belt,the Qilian Mountains seismic belt and the corridor seismic belt.As a result,the Great Wall in Hexi region is vulnerable to the earthquake and further damage or even collapse.Through the method of consulting documents and investigating on the spot,we found that the preservation situation of The Great Wall was not optimistic and most of them were seriously damaged.The wall were not protected very well look like some kind of ridge and their remaining heights were about 0.5m.On the other hand,the heights of the wall with good condition were from 3m to 6m.By conducting indoor soil test,we draw a conclusion that the dynamic elastic module of The Great Wall were all over 100 MPa,and the dynamic elastic module of soil from the Beacon Tower is the biggest,while the value of number reaches to 129.87 MPa.The experimental results also show that the values of damping ratio were from 0.063 to 0.133.And then large number of pebble in the wall made the value of internal friction angle more than 30°.56.71° which is the largest value is from the Great Wall Township.Cohesive force change from 19.17 kPa to 157.64 kPa and strength of extension cover from 0.1MPa to 0.3MPa.Based on finite element software,six numerical models of the Great Wall and The Beacon Tower were built respectively.After inputting Shandan 6.1 magnitude seismic wave,the results are summarized as follows.(1)The Great Wall of Huang Yang river farm is in a basically stable state,but the few regions of the wall bottom will produce crack and fall.The maximum tensile stress is located at the bottom of the wall.Because the secondary wall plays a reinforcing role,the acceleration and displacement of this region is less than other region.(2)The Great Wall of Jin Chuan Xi will have a large area of cracking in basal sapping region,so the Great Wall is likely to collapse.The maximum tensile stress is located at the basal sapping region.Acceleration and displacement increase with the altitude of the wall.The basal sapping has great influence on the stability of the Great Wall,the basal sapping must be taken seriously.(3)The Great Wall on the north side of Wang Xin Bu is in a basically stable state,the maximum tensile stress is located at the bottom of the wall.Acceleration and displacement increase with the altitude of the wall.(4)The Great Wall of the Great Wall Museum of Shandan will have a large area of cracking and collapsing in passageway periphery,so the Great Wall is likely to collapse.The maximum tensile stress is located at the passageway periphery region.Acceleration and displacement of the wall above the passageway is the largest.The acceleration and displacement of this region are greater than other region.As a result,the existence of the passageway makes the structure of the Great Wall damage,under the action of the earthquake is likely to collapse.(5)The No.5 Beacon Tower of Yanchi is in a basically stable state,but the few regions of the Beacon Tower bottom will produce crack and fall.Due to the special shape of the Yanchi No.5 Beacon Tower,the acceleration and displacement of the Beacon Tower top are very large,there is a significant amplification effect.(6)The Beacon Tower of Jinta is in a basically stable state,but the few regions of the Beacon Tower bottom will produce crack and fall.The maximum tensile stress is located at the four corners of the bottom of the Beacon Tower.Acceleration and displacement increase with the altitude of the Beacon Tower.The maximum acceleration and displacement is located at the four vertex parts of the Beacon Tower.As a whole,The Great Wall is destroyed under the earthquake of eight degrees intensity.Under the action of the earthquake,the Great Wall that structure has been destroyed is likely to produce collapse.Due to the greater risk of earthquakes in the Hexi area,it is necessary to reinforce the Great Wall that structural have damaged.