Military Defense System And Vulnerability Assessment Of Earthen Sites Of The Ming Great Wall In Qinghai Province

As one of the world's ancient civilizations,China owns a long history and rich cultural heritage.With high historical,artistic,cultural,social,and scientific values,these cultural heritage contains unique spiritual values,thinking modes,and imagination of the Chinese nation,which reflects its great creativity and vitality.Being a world cultural heritage site,the Great Wall built in the Ming Dynasty,called the Ming Great Wall,is the largest and best-preserved Great Wall project in Chinese history.Due to the scientific construction principles and exquisite construction techniques,the Ming Great Wall has been deemed as the representative of the Great Wall.Talking about the Ming Great Wall,it is well known that it is from Shanhaiguan in the east to Jiayuguan in the west.However,the truth that the Ming Great Wall has been existed in Qinghai Province was rarely concerned.Experienced natural erosion and human destruction for hundreds of years,the main body of the Ming Great Wall in Qinghai Province has been existed as the form of earthen sites.The earthen sites of the Ming Great Wall were mainly made of rammed earth,which is a kind of special earth mass directly affected by the environment.In the long interaction of atmosphere,hydrosphere,biosphere,and lithosphere,their safe occurrence has been seriously threatened by temperature,rainfall,sediment-carrying wind,salinization,and human activities.In turn,such earthen sites have been undergoing a process from quantity to quality,namely the development from some typical deterioration types including cracks,gullies,sapping,scaling off and collapses on earthen sites to the fate of extinction.As the Ming Great Wall in Qinghai Province is located in a corner place which is an alpine-cold and high altitude region,its occurrence environment and defense system have the particularity.Therefore,the exploration and generalization of the Ming Great Wall Military Defense System(M-GWMDS)in Qinghai Province and the study on the vulnerability assessment of its typical earthen sites would not only supplement and improve the scientific research system of the Great Wall distributed in this area and further characterize the occurrence,development,and process of deteriorations on earthen sites under the influence of special environment in Qinghai-Tibet Plateau,but also have important guiding significance and application values to decide scientific and practical protection measures and make systematic planning work.In light of the above understanding,this paper takes the earthen sites of the Ming Great Wall in Qinghai Province as the research object.Starting with the research about the characteristics of the occurrence environment and materials properties of rammed earth,the preservation scale,architectural forms,and distribution characteristics of building types of the Ming Great Wall have been systematically explored,and the constitution features of the M-GWMDS in Qinghai Province have been clarified;The development types and scales of deteriorations at such earthen sites have been completely investigated and summarized,and combined with the occurrence environment of earthen sites,building technology of the Ming Great Wall,and building materials characteristics,the frame system of deteriorations of earthen sites of the Ming Great Wall has been preliminarily established;Multi-Criteria Decision Making(MCDM)methods were applied to evaluate the vulnerability of earthen sites,and then the model of the vulnerability assessment of earthen sites has been constructed.After that,by applying machine learning methods to train and test the vulnerability scores obtained before,the prediction model of the vulnerability assessment of earthen sites of the Ming Great Wall in Qinghai Province has been established.The main research content and results are as follows:(1)Based on previous research results and a lot of field investigations,the occurrence environment and conservation scale of earthen sites of the Ming Great Wall in Qinghai Province have been systematically summarized,and it is concluded that the distribution area of earthen sites of the Ming Great Wall is high in elevation and low in temperature all year round.Thus,their occurrence environment has characteristics with higher altitudes and lower temperatures.The architectural forms and distribution characteristics of the mainline wall,beacon towers,and castles of the Great Wall have been clearly explored: the mainline of the Ming Great Wall was distributed with an arched shape closely surrounding Xining Wei that is the center in the M-GWMDS;the beacon tower has spot and linear distribution characteristics,and the linear distribution is mainly reflected by the beacon tower links;meanwhile,according to military functions characteristics,the castles have 7 types,namely Wei,Suo,courier station,the castle for garrison,Tusi's office or residence,horse keeping castle,and unofficial castle.Through consulting literature materials,the specific functional classifications of all 46 castles were extrapolated and obtained,combined with the features of circumferences threshold,architectural forms,and distribution of castles.(2)Based on the shape features and military functions of various types of buildings of the Ming Great Wall,the research about the spatial distribution of castle-based military settlements,force distribution,defense districts division,and reachable domain of troops was carried out.The military deployment in the M-GWMDS was analyzed from the time and spatial dimensions.In further,the author explored to comprehensively research the M-GWMDS,which contains four elements,i.e.,the Great Wall mainline,castle-based military settlements,beacon tower system,and the relay system.Such components have made up a close network to defense,attack,and transfer vital information,documents and staff with high-efficiency cooperation among each functional architecture of the Great Wall system.(3)Through the detailed investigation and statistics on the deteriorations developed on the typical earthen sites of the Ming Great Wall in Qinghai Province,cracks,gullies,sapping,scaling off,and collapses are regarded as the most prevalent and representative deterioration types.Based on the qualitative judgment of the sites deteriorations relationships with their occurrence environment,engineering properties of construction materials,and building technologies,the characteristic values of deteriorations were analyzed quantitatively with meteorological data of distribution area of sites and indices of engineering properties of rammed earth,to obtain the internal relationships among deteriorations;In the meantime,the main influencing factors of deteriorations development of earthen sites include the physical,water-physical,and mechanical properties,the occurrence environment that is mainly focused on exogenic forces containing precipitation and wind,and the building technology.On the basis of the above results,the frame system of deteriorations developed in earthen sites of the Ming Great Wall in Qinghai Province was preliminarily established.(4)According to the frame system characterizing deteriorations developed on earthen sites of the Ming Great Wall in Qinghai Province,the hierarchical structure of vulnerability assessment can be constructed.By using Analytic Hierarchy Process(AHP),the weights of evaluation indices were calculated,and then the vulnerability of 18 typical sites was evaluated by applying FAHP and AHP-TOPSIS to determine their vulnerability scores and collapses damage levels.Compared with the actual development scale of deteriorations at earthen sites,AHP-TOPSIS was determined as a more suitable evaluation methodology for the vulnerability of earthen sites of the Ming Great Wall in Qinghai Province,and its calculated results were consistent with the degree of the actual collapses caused by deteriorations development.Hence,the reasonability of the assessment model and methodology of the vulnerability of earthen sites of the Ming Great Wall in Qinghai Province has been verified.(5)Utilizing two typical and effective machine learning methods,i.e.,SVM and BP Neural Network,the obtained vulnerability scores of selected earthen sites were divided into training and testing groups.After adjusting parameters,training,and testing data,the vulnerability prediction of the earthen site of the Ming Great Wall in Qinghai Province was realized.By comparing the predicted results and actual damage levels of earthen sites,SVM has a better prediction result through calculating related accuracy parameters.Thereout,the prediction model of the vulnerability of earthen sites of the Ming Great Wall in Qinghai Province was built.