Hazard Assessment Of Large Collapsed Body In Limestone Area Of Reservoir Area

In China,dangerous rock avalanches mainly occur in the central and western mountainous areas,especially in the three gorges reservoir area.With the vigorous construction of highway,railway,water transportation and other transportation infrastructure in China,collapse disasters have an increasingly close relationship with our life and may cause great harm to the safety of our lives and property at any time.Therefore,it is imperative to study the formation mechanism and hazard assessment of large collapsed body in the limestone area of the reservoir area.This article from the forming mechanism of the large collapsed body of the limestone region,using the analytic hierarchy process(AHP)and fuzzy comprehensive evaluation method to establish the fuzzy comprehensive evaluation model.The hazard assessment of the large collapsed body of Jiwei Mountain in Wulong county and the large collapsed body of Mozi Rock in Hechuan county is carried out,and the applicability of the evaluation model is verified.The hazard of collapse disaster in Wushan county was evaluated by ArcGIS software.The main research results are as follows:(1)Taking the large collapsed body of Jiwei Mountain in Wulong county and the large collapsed body of Mozi Rock in Hechuan county as examples,the formation mechanism of the large collapsed body in the limestone area of the reservoir area is analyzed from the aspects of topographic and geomorphic conditions,stratigraphic lithological conditions,geological and tectonic conditions,rainfall,weathering and unloading and the influence of human engineering activities.(2)Through the analysis of the formation mechanism of large collapsed body in the limestone area of the reservoir area and the reference of relevant research literature and expert opinions,the hazard assessment index system is established by selecting 10 assessment indexes,including the height of the steep cliff,the structural characteristics of the steep cliff,the geological structure of the steep cliff,the scale of collapse body,the dip Angle of the main control structure surface,the penetration degree of the main control structure surface,daily maximum rainfall,weathering,seismic intensity and human engineering activities.Hazard assessment index can be divided into low hazard(?),medium hazard(?),high hazard(?)and extremely high hazard(?)four levels.By combining the analytic hierarchy process(AHP)and fuzzy comprehensive evaluation method,a fuzzy comprehensive evaluation model of the hazard of large collapsed body in limestone area of the reservoir area is established.The applicability of the assessment model is tested by two engineering examples of the large collapsed body of Jiwei Mountain in Wulong county and the large collapsed body of Mozi Rock in Hechuan county.The assessment results are in line with the actual situation,which indicates that the established fuzzy comprehensive assessment model for the hazard of large collapsed body in the limestone area of the reservoir area has good applicability(3)Taking the collapse hazard of Wushan county in the three gorges reservoir area as the research object,eight assessment indexes,including geomorphic type,topographic relative height difference,topographic slope,stratigraphic lithology,distance from fault structure,average annual rainfall,vegetation coverage and land use type,were selected to establish a hazard zoning assessment index system.The analytic hierarchy process(AHP)is used to determine the weight coefficient of evaluation indexes,and the comprehensive assessment index model of collapse hazard is established.(4)Using ArcGIS software to generate single factor figure of geomorphic types,single factor figure of the relative difference,single factor figure of the slope degree,single factor figure of the formation lithology,single factor figure of the distance from fault structure,single factor figure of the annual rainfall,single factor figure of the vegetation coverage and single factor figure of the land use type.According to the criteria for index classification and valuation,the single factor figure of the assessment index was reclassified and converted into single factor hazard partition assessment figure.(5)By using the spatial superposition analysis function of ArcGIS software,the single factor hazard partition assessment map of 8 assessment indexes was superposed and analyzed,and the composite index diagram of collapse hazard in Wushan county was obtained.Hazard composite index can be divided into four levels,and the zonal assessment figure of collapse hazard in Wushan county was got finally.It can be concluded from the zonal assessment figure that the areas of low hazard,medium hazard,high hazard and extremely high hazard respectively account for 17.98%,36.39%,31.47% and 14.15% of the total area of the county.According to the statistics of towns and streets,there were 6 towns and villages in the extremely dangerous area,9 towns and villages in the highly dangerous area,8 towns and villages in the moderately dangerous area,and 1 town and 2 streets in the low-dangerous area.