Hazard Assessment Of Landslide In Fujiang River From Nanba To Shuijing

The upper reaches of the Fujiang River from Nanba to Shuijing is located in the northwest of Sichuan Mianyang,affected by the Songpan earthquake belt and the Longmen Mountain Fault Zone,the secondary earthquake disasters are very developed,and rainfall in the area is relatively concentrated,which often induces a large number of landslides.These geological disasters have significant influence on the geomorphic evolution of the river valley and the human engineering activities.Consequently,it is of great theoretical and practical significance to find out the distribution law,development characteristics and risk of the landslide.Combined with the field investigation and related data,the landslide distribution law,development characteristics and formation mechanism are studied on the basis of systematic study of landslide hazard in the study area.On this foundation,the main influencing factors of landslide formation is selected,establishing the landslide risk assessment index system is establishing,and adopting the AHP-CF method to build a landslide hazard assessment model by ArcGIS software,thus completing the partition of danger zone landslides in research area,research achievements and conclusions are as follows:(1)The study area is the transition area of Sichuan Basion to Qingzang-Tibet Plain,and the overall terrain topography is higher in the northwest and lower in the Southeas,which is mainly the middle-high mountain landscape.The exposed strata of the area vary in large,there are pre Sinian,Sinian,Silurian,Devonian,etc,and the lithology is mainly metamorphic sandstone,phyllite,crystalline limestone etc.In terms of geological structure,mainly including Nanba fault,Qingxi fault and Huya fault,and a series of folds structures.(2)By analyzing the development regularity of the 157 landslides in the study area,the scale of which is mainly medium to large,and the density of dry streamline is 0.67/km,and the density of landslide is up to 3.33/100 km.On this basis,the distribution law of landslide(spatial distribution,time distribution,etc.)and development characteristics(shape,scale,material composition,present activity,etc)are analyzed and compared.(3)With research on the typical landslide and the foundation of development regularity of landslide in the study area,the influencing factors of landslide disaster are synthetically selected: topography,lithology,geological structure,geological structure,river system,human engineering activities and rainfall,etc,among them,rainfall and human engineering activities are the inducing factors,and other factors are internal factor.By ArcGIS platform,each of the factors about the distribution of landslide is statistically analyzed,and results show that t the elevation of landslide 1000 ~ 1500 m,15 ~ 30 degrees,slope towards the south is the most sensitive,and the landslide has the highest density in the stratum lithology of the soft rock and the soft and hard rock stratum,and the consequent slope structure is the most favorable for landslide occurrence.(4)Combined with geologic background and previous research results,the formation mechanism of landslide types are divided into five types: creep-fracturing mode,sliding-fracturing mode,toppling(bending)-fracturing-sliding-fracturing composited mode,crack-bedding slip mode,ladder sliding-fracturing type.(5)By means of establishing the index system of landslide hazard assessment,with the certainty factor(CF)and analytic hierarchy process(AHP)model,combining the objective factors and the actual situation,the hazards assessment and regionalization of the landslide in the study area are carried out.The evaluation results show that the stratum lithology,slope structure,rainfall and river factors of landslide disasters is prone to the relatively large contribution.According to the geometric discontinuity method,the study area consisted of four hazard levels,which were extremely dangerous area [0.0064~0.5761],high hazard zone[-0.2711~0.0064],medium danger area[-0.4063~-0.2711] and low hazard zone[-0.6836~-0.4062].The rationality of the model is checked by ROC curve,and the AUC value was 88.36%,which shows that the accuracy of the model is very accurate,and the evaluation model can objectively and accurately evaluate the landslide hazard in the study area.