Methods On Risk Assessment And Monitor&Early-warning For The Loess Landslide In North Of Shannxi

Loess landslide is a kind of geo-hazard which wildly developed in northwest loesspleatue. This thesis took the loess landslide in Zizhou county, Suide county and Baotadistrict in north of shaanxi province as the researching object. It investigated plenty ofloess landslides in the field, analyzed its typical geological environment, triggered factors,mode of deformation and failure, and characteristics of risk. It also analyzed the riskcharacteristics of loess spall, topple, fall, collapse, slide and earth flow comparatively.It applied the international landslide risk management theory which were developedrecent years to the practice of study area, divided the risk assessment into four layer whichare small scale, middle scale, large scale and single landslide scale with different accuracyaccordingly. It distinguished the difference and relationship among susceptibility, hazardand risk, and did the case study using the landslide data from Yannan Baota area. The1:50000small scale risk assessment is appropriate for the whole area, it can be obtainedby the traditional griding and information value calculating method. The1:25000middlescale risk assessment is appropriate for the urban areas, economic development zones, orimportant towns, it can be obtained by following steps: firstly it identifies thesusceptibility area through overlying the high accuracy DEM and the Quick Bird remotesense image; secondly it circles the dangerous areas of the landslides; thirdly it interpretsthe elements in the risk; finally it makes the checks in the field. The1:10000large scalerisk assessment is appropriate for the important slope zones, it can be obtained bydesigning a slope’s classifying system then scoring a grade to implement. The>1:5000scale risk assessment is appropriate for the single landslides, it can be obtained byanalyzing the stabilities through the reliability methods, and calculating the property lossrisk, individual life loss risk, and societal life loss risk respectively. For all it achieved asystem of risk assessment methods for north of Shannxi’s loess landslides.On the basis of field investigation and observation it preliminary established threerainfall infiltration and triggering modes which are slow-infiltration triggering mode,infiltration-blocked triggering mode and integrated-infiltration-passage triggering mode. Itanalyzed the rainfall infiltration process and loess landslide triggering mechanismsqualitatively. It collected227landslides cases which having certain date records andoccurred in1960~2008, divided these cases into three groups according to the modes,used correlation and logistics statistical methods to study the relationship betweenlandslides and rainfall, and established the rain thresholds for each infiltration andtriggering modes respectively.It discussed the suitability of the monitoring methods and techniques according to thedeformation and failure features of the loess spall, topple, fall, collapse, slide and earthflow. It studied the layout principles of the rainfall stations in region and its installation methods, illustrated the rainfall monitor of Yannan Baota district. It studied the singleloess landslide’ monitoring methods, took Baotashan landslide as the example, analyzed itsfour years monitor curve, and draw a conclusion that this landslide is still stable.According to the results of risk zoning on a different scale and the thresholds in threecatalogues, it set the early-warning indexes and its levels, and developed the regionalearly-warning model. It took the Yannan Baota district as the example, studied thegeo-hazards monitoring and early-warning system that should suitable to a county. Itintegrated the rainfall monitors, single landslide monitors, simple equipment monitors andmanual inspections into the system, divided the county’s early-warning into four levels assmall scale, middle scale, large scale and single landslide scale which have differentaccuracy respectively. Finally it designed a management system that can service thetechnical support for the county government to manage the geo-hazards.