| Qinggan River is composed by Luogudong River, Meijia River and Guiping River. In the river basin, the most major environmental geological problems is Geological Hazards, in recent years, human engineering activities frequently, such as coal mining, immigration relocation, engineering re-Construction etc, and suffer the influence of the impoundment of Three Gorges Reservoir,Slope stability condition are further deterioration. shortly after impoundment of Three Gorges Reservoir, it took place more than one the collapse, landslides, and Deformation phenomena of the bank slope. Therefore, it is great significance to analysis the different Instability modes and stability state of the Bank slope of Qinggan River for prevention and control of Geological Hazards.On the basis of the details investigation of the geological condition of the study area, this thesis partitions the types of bank slope and separates the bank from them, analyses the deformation and failure law, study the deformation and failure modes and controlling factors of bank slope. At last, it evaluates the stability of the bank slope in segments and takes measures against the unstability of the bank. The main conclusion is as the following:(1) Study area of the Qinggan River, total length 92.5km, through the investigation and analysis of structure types of bank slope, lithology and lithologic features, structural features of rock mass, the types of bank slope of the study area could be divided into 47 paragraph and 17 Types.(2) In the study area, the major controlling factors of deformation and failure modes and stability state of the bank slope are structure types of bank slope and lithology and lithologic features. The bank slope is mainly of gentle layered structure and reverse structure in distribution area of carbonate rock, geological disasters less developed, only discover small collapse. The distribution area of soft clay rock is more slump-mass with Small-scale and high frequency. However, the distribution area of hard and soft lithologic combination or Coal-bearing rock group Sandwich with consequent structure of bank slope offen is large landslide, the most damaging, when it is reverse, horizontal structure, usually, that is a few geological disasters with insequent landslide or collapse.(3) Considering the controlling factors, instability mode of bank slope could be divided into two stypes.the first type,the controlling factors is lithology and lithological combination.the second type,the controlling factors is structure types of bank slope.the first type can be Subdivision into:a,unloading-tension fracture mode of the dumping of collapse in hard, harder than the middle-karat layered carbonate bank slope, b,Sliding-tension type of slump-mass in bank slope of soft clay rock with a "soft-hard structural surface," by a different degree of weathering. The second type can be Subdivision into:a,Slip plane type,slow Sliding-tension,Sliding-Shear in consequent structure of bank slope,b,insequent landslide with plastic flow-cracking and creep-cracking in reverse structure of bank slope,c,evolution modelof landslides and collapse Promote each other in oblique or Transverse structure of bank slope.(4) Rainfall, corrosion and anthropic engineering activity are the three main inducement of the deformation and breakage about the bank slope in the reservoir area.(5) Under the influence of lithological cycle and river erosion, evolution process of consequent bank slope or inclined consequent bank slope of study area can be divided into four phases:Stable rock slope—Unstable rock slope—Distorting rock slope—Landslide dying-away, and which are embodied by the actuality of the bank slope and staggered & periodic. And through, different characteristics of each stages of evolution of the bank slope,. this thesis put forward a method to evolution stability of bank slope and control measures recommended based on the analysis of evolution process of bank slope.(6) This thesis apply qualitative method and Fuzzy Comprehensive Evaluation to evaluates and forecast stability state of the bank slope.The results show that the proportion of the Paragraph of good stability Slope is 82.9%,length of bank slop is 79.7%,that the proportion of the Paragraph of poor stability Slope is 17.1%,length of bank slop is 20.3%.in the Luogudong River, The results show that the proportion of the Paragraph of good stability Slope is 66.7%,length of bank slop is 62.0%,that proportion of the Paragraph of poor stability Slope is 33.3%,length of bank slop is 38.0%.Generally speaking, Slope stability is in good condition,but the less well-off Slope bank are located in densely populated, frequent human activities, it is Great harm to people.(7)Based on the actual condition of the bank slope in study area, it takes the meatures to prevent the bank slope off its unstability:inspecting and forecasting, preventing rainfall and surface water from infiltrating, preventing the backyard of the slope from loading severly, preventing the frontage of the slope from corroding and unloading, comprehensive treating, exploiting land resources protectly and so on.
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