Risk Assessment Methods For Earthen Sites Deterioration In Arid Area Of Northwest China And Application

Earthen sites in northwest arid area are an important part of our cultural heritage.Most earthen sites are exposed to the open air and are constantly threatened by rainfall,wind and sand.The ontological deterioration of earthen sites under the action of various risks,that is,the deterioration process of slow loss accumulation caused by natural inducement,usually manifests as the disease of earthen sites.The development of diseases poses a challenge to the preservation of earthen sites.With the advancement of the conservation of cultural relics in our country,the concept of conservation has gradually changed from rescue protection to preventive protection.Risk management is a common means of preventive protection,in which reasonable risk assessment is an important step.Risk assessment of deterioration risk of earthen sites in northwest arid region can not only allocate limited protection resources reasonably,but also provide theoretical and technical support for the construction of a scientific and reasonable risk monitoring system.On the basis of systematically sorting out the existing methods of cultural heritage value assessment,this study puts forward the method of value assessment for earthen sites in northwest arid region,so as to ensure the correct scientific cognition of the value of earthen sites.Combined with literature review and field research,the disease types and degradation causes of earthen sites in Northwest China were systematically analyzed,the risk sources of earthen sites in arid northwest China were clarified,and the risk summary was written.Finally,a list of earthen sites deterioration risk factors was formed as an important basis for risk identification.Based on ABC method and risk matrix idea,a risk assessment method of earthen site deterioration in northwest arid region was constructed,and an application demonstration of the risk assessment method was carried out by taking the inner city site of Suoyang Ancient City in Guazhou City as an example.The research has made the following achievements and understandings:(1)This paper puts forward a method of value cognition and value evaluation of earthen sites in northwest arid area,which combines qualitative evaluation and quantitative evaluation.The qualitative evaluation mainly needs to consider historical value,artistic value,scientific value,social value and cultural value.A value evaluation method that can realize quantitative evaluation is constructed.This method needs to decompose the evaluation object into several value carriers,assign weight to five value components,evaluate the contribution of each value carrier in five value components,and finally get the value pie chart of relative value percentage.(2)According to the existing research results,the main diseases of earthen sites in northwest arid region include sheet denudation,gully,fissure,collapse,cutting and biological diseases.The deterioration of earthen sites and the formation of these diseases all have the characteristics of slow loss cumulative risk.The main risk sources include wind(sand),rainfall,snowfall,air humidity,air temperature,solar radiation,soluble salt,human activities,groundwater,surface water,animals,plants and microorganisms.According to the process of deterioration of earthen sites to form diseases,a list of risk factors including risk consequences,risk events and corresponding risk sources is obtained.(3)Combined with the characteristics of earthen sites in northwest arid region,a risk assessment method of earthen sites deterioration based on the precautionary principle,comprehensiveness principle and continuous improvement principle was constructed.The assessment method mainly includes risk assessment preparation,risk identification,risk analysis and risk evaluation.Before risk assessment,it is necessary to clarify the basic needs of risk assessment,and collect relevant information and value assessment.Risk identification combines 12 kinds of deterioration inducements and 2 kinds of risk action modes to identify risks.Risk analysis takes into account the frequency of risk(probability),the degree of loss of value,and the percentage of value of the risk impact.The calculated risk grade score can be used to evaluate the risk,and the evaluation results are divided into highest priority,high priority,medium priority,low priority and negligible priority.(4)The inner city site of Suoyang Ancient City in Guazhou can be divided into five value carriers: wall,barbican,horse wall,horn pier and watchtower.Through field investigation and data collection,it is found that the main diseases of the inner city site of Suoyang Ancient City are lamella erosion,crack,gully,erosion,collapse and biological diseases.Combined with the investigation of its occurrence environment and the analysis of meteorological data,Nine risk sources including wind(sand),precipitation,air humidity,air temperature,solar radiation,soluble salt,groundwater,plants and animals were identified,and risk levels of each value carrier in the inner city site of Suoyang Ancient City were obtained,among which 1 were high priority,3 were medium priority,2were low priority and 3 were negligible priority.