Study On The Method Of Landslide Hazard Rank Division

Landslide is a common geological disaster, traffic facilities, construction, hydropower projects, factories, mines, fertile farmland, tourism resources, ecological environment and so on, are often destroyed, which seriously affects the industrial and agricultural production and economic development of disaster area, causes a long period of economic chaos, population migration and the negative effect on natural environment. How to deal the relationship between population, resources, environment, disaster prevention and mitigation is particularly critical. Landslide hazard zonation, analysis of slope stability and estimation of landslide affected areas can maximumly reduce the impact of the landslide hazard on human life, promote the sustainable development of social economy, it is a practical significance work.On the basis of a case study regarding the geographical conditions of Sichuan, according to the related materials of Sichuan, this paper studied on the landslide hazard rank division in Sichuan with the method of pattern recognition, improved algorithm through control tests, the study area was divided into seven rank divisions; PFC3D was used to simulate Jiweishan landslide in Wulong, and gave some preliminary analysis and discussion. The main contents could be summarized as follows:(1) Landslide formation mechanism and landslide environment of study area were introduced, landslide major effect factors were chose and quantified, the study area sampling units and factor weight were determined, a preliminary landslide hazard factor zoning evaluation system was established.(2) All the units were primary classified, historical landslide record was used to revise classification results, using pattern recognition method to carry on the landslide hazard rank division. A series of control tests were conducted on danger coefficient formula, weight of factor, selection of threshold and so on, to improve the accuracy of the zoning. Index of "identify rate" and "change rate" were proposed for the method which took the high identify rate and steady change rate as classify standard, the rationality of zoning results was validated finally. Altogether three times recognition were taken to realize seven rank divisions in landslide hazard of Sichuan, the result from pattern recognition method coincided well with landslide occurrence. The method also can be used for other region’s landslide hazard rank division.(3) PFC3D, one of the discrete element methods, is carried out to simulate Jiweishan landslide. Complex bedrock geology was simulated using triangular wall elements. Sliding mass was simulated using clump elements and generated using drop accumulating method. The landslide process of Jiweishan was then simulated using selected contact parameters. The effect of microscopic parameters on slope stability, sliding speed and sliding distance was discussed. The result of numerical simulation, such as accumulation shape, sliding distance and landslide process, was consistent with the reality. The study shows that Jiweishan landslide is an apparent dip slide and shear rupture with the characteristics of high-speed and long distance. Contact bond strength, friction coefficient of particles and walls affect slope failure pattern directly.