Disease Development Characteristics And Risk Assessment Of The Piers In Jiayuguan

Earthen sites are the relics of ancient human activities,reflecting the production and life of human beings,the natural environment at that time and the changes of human beings to the environment.They have unique historical,cultural,social and scientific values.However,the preservation of earthen sites is poor under the influence of external environment.Jiayuguan Ming Great Wall is a world cultural heritage,the best preserved and most functional ancient military pass at home and abroad.However,with the passage of time,the Great Wall has been constantly disturbed by the external environment and human beings,and the preservation situation is deteriorating.Therefore,it is very important to investigate and study the disease of Jiayuguan Ming Great Wall.This paper takes the pier and abutment site of Jiayuguan as the research object,obtains the architectural form information through the field survey,and explores the construction technology and system of the pier and abutment based on the historical data and other research data,so as to lay the foundation for the disease research.Through the sampling and investigation of the pier and abutment,the main parameters and samples of the disease development are obtained.Combined with the test,the specific property information and parameters of the pier and abutment site soil are obtained.The characteristics and laws of the disease development of the pier and abutment site are summarized based on the investigation data,and the basic evolution route of the disease development is finally obtained.Through the introduction of AHPDEA analysis method to evaluate the risk of pier and abutment disease development,in order to get a widely used method in the risk assessment of earth sites.The main conclusions of this paper are as follows:(1)There are many defense routes in Jiayuguan area,forming a defense system with two wings and one city as a whole.There are five types of piers: solid,hollow,along the border,outside the belly and inside the belly.The main construction techniques include loess ramming,loess sand ramming,adobe laying and stone laying.(2)According to the test,the site soil in Jiayuguan area is low plastic clay in silty clay,with strong water sensitivity,low soluble salt content and high compressive strength in the site soil of adobe laying piers,high soluble salt content in the piers of loess ramming and loess sand ramming,and most of the site soil is saline soil with low compressive strength.(3)According to the correlation analysis between the disease and the internal and external environment and the disease,it is considered that the development of the basal sapping disease has a good correlation with the soil particle content within the 0.075mm-0.25 mm particle size range,soluble salt content and tamping technology.The development of the collapse disease is related to the compressive strength of the soil,the construction technology and the development degree of the basal sapping disease;the development of the fracture disease is related to the plasticity index of the soil.The development of gully disease is closely related to soil disintegration rate,liquid limit and crack disease.(4)The AHP-DEA evaluation model ranks the collapse disease as the most dangerous,the basal sapping disease as the second,The risk of crack disease is higher in rammed earth pier,lower in adobe masonry pier,and the risk of gully disease is the same in rammed pier and adobe laying pier,and the development of the spin-off sheet disease has little effect on the risk of the pier site.