Research On Risk Zoning Of Geological Hazards In Liuba County Of Shaanxi Province

Recently, accidents about dead and injured people and property loss are becoming more and more frequently because of geological hazards and it is catching people's more and more attention. This thesis focuses on Liuba county, located in the northern mountain area of Hanzhong City, Shaanxi Province, and does research on risk zoning of geological hazards in Liuba county.This thesis is based on fully gathering physiogeological, phenomena and hydrological as well as regional geology data and information of Liuba county, and combines them with investigation outcomes of geological hazard sites. After analyzing the developing features and forming mechanisms of geological hazards, this thesis develops risk zoning with comprehensive evaluation based on GIS and fuzzy comprehensive evaluation. Consequently this thesis separately gets results of risk zoning derived from these two methods, draws charts further, briefly analyzes the difference between the results and gives some feasible suggestions to prevent geological hazards. The core contents of this thesis are listed as follows:(1) This thesis analyzes distribution character, developing features and forming conditions. The main hazards in Liuba county include landslide, slide, mudflow and unstable slope. With the impact of landform and geomorphy, meteorological and hydrological conditions, powerful new construction movement and human activities on geological hazards, distribution character in Liuba county is different from area to area. Geological hazards are very scarce in high and low mountain area, while they are richly developed in low mountain and valley area and are unbalanced between each town. The developing features are summarized as group character, periodic property, unplanned property and correlated character. The forming conditions are introduced from intrinsic factors and induced factors. The intrinsic factors are landform and geomorphy, layer rock character, hydrologic geology, and so on, while the induced factors are made up of climate factors and human engineering activities.(2) Whole Liuba county is divided into high risk zone, middle risk zone and low risk zone. Evaluation index system is set up by choosing seven concrete evaluating indicators, including density of geological hazard, height of slope, slope, and breakage distribution, petrofabric of engineering geology, rainfall and impact of human activities. And the weight of each evaluation index is calculated with A.H.P.(3) This thesis develops risk zoning of geological hazards with comprehensive evaluation based on GIS, using elevation figures of contour lines for generating DEM on the basis of the digital geological map with a scale of 1:50000 and detailed survey data and information of geological hazards in Liuba county, dividing declivity elements into evaluation units, developing weighted overriding analysis after extracting layer of seven evaluation indicators and concluding high risk zone, middle risk zone and low risk zone.(4) Fuzzy comprehensive evaluation is used for developing risk zoning of geological hazards based on evaluation units of 1 km×1km and membership grade derived from trapezoidal function and finally concludes high risk zone, middle risk zone and low risk zone of entire Liuba county.(5) Comparing the risk zoning result from comprehensive evaluation based on GIS with the conclusion from fuzzy comprehensive evaluation, they are relatively similar to each other and match the reality. At the basis of risk zoning, contermeasures and advice are given to prevent and even eliminate geological hazards.