A Study On Landslide Susceptivity Classification And Rainfall Threshold In Wanxiu District Of Wuzhou City In Guangxi Zhuang Autonomous Region

Regional landslide is one of the major geologic hazards in our country, which features large areas of damage, simultaneity, sudden breakout and serious consequences. Due to much uncertainty of landslide occurrence,the integrated approach of multi-parameter indicators is accepted in regional landslide assessment .So landslide susceptivity classification is always hot focus of landslide study .The theory of landslide hazard zonation is a complex systems engineering, the paper expatiate detailedly this system which include how to set up mainly factors and measurable factors and math's model and confirm the hazard degree and gain the result of hazard zonation etc, So carrying landslide susceptivity classification have very important practical significance.Combining a key project"geologic hazards assessment and prospecting and design in W anxiu district of wuzhou City"provided by Guangxi Zhuang Autonomous Region geo-environmental monitoring station, Wanxiu district of wuzhou City is chosen as the research target in the paper. Based on the rich practical data, the paper makes the in-depth research into various factors affecting the occurrence of landslide, conducts an overall analysis on the relationship bettween the time-space distribution of landslide and rainfall, and explores the method to determine the threshold of rainfall inducing the regional landslide. It also preliminarily establishes the susceptivity of classification of regional landslide system. Based on the test of the data of landslide and rainfall threshold in the research area in 2005 and 2006.all approaches are practical, feasible and can provide scientific basis for the active disaster mitigation and prevention. The key researches, approaches and conclusions are as follows:Sensitivity analysis on the landslide impact factor in the research area is carried out by using the landslide weight coefficient: Key factors affecting the landslide in the research area are determined by the consolidated inspection on the weight coefficient. Logic statistical analysis predictive model is established, and through homogeneous meshing, the space quantitative evaluation on landslide susceptivity is realized. The paper proposes the weight logic regression model to address the consolidation of different data layers during the landslide critical evaluation through GIS-based statistical analysis model and the determination of data layer superposition weight. By combining the weight coefficient and logic regression model (Binary Logistic) and with the assistance of SPSS statistical analysis software, the factor selection, heterogeneity data consolidation and the data layer superposition weight are solved and the precision and efficiency of landslide susceptivity zoning are improved. Research shows that landslide is mostly likely to happen at the second river vally terrace sandstone with interlacing softness in Wanxiu district, dip slope of >60°facing the east and southwest as well as the forestland and human effect area with elevation between 50-100 m. Key factors affecting the landslide risk include the aspect of forestland, human effect area, slope, elevation, petrofabric, inclination of slope . Based on the calculated cell landslide probability of occurrence, the landslide risk in Wanxiu district is divided into 5 grades, namely extremely unstable, unstable, latent unstable, basically stable and stable.Inspection is carried out on the new landslide sites of Wanxiu district in 2006. The result shows that the extremely unstable area and unstable area contain 86% of the verified landslide, indicating that the evaluation result is in reasonable agreement with the actual landslide.Based on Logic regression model, the regional landslide threshold expression and the probability of rainfall's impact on the landslide is established. Quantitative investigation has been conducted on the expressed rainfall precipitation for the rainfall threshold inducing the regional landslide based on the logical regression coefficient. Expression considering both the rainfall intensity and rainfall threshold during the rainfall is established.Research indicates that the occurrence of landslide in Wanxiu district is relevant to the rainfall during the 2 days, i.e., the rainfall of the same day (1-day rainfall), the rainfall of the day before (2-day rainfall); Of that, 1-day rainfall has the maximum impact on the occurrence of landslide. The rainfall precipitation expressed by rainfall threshold is determined as the accumulative rainfall of the rainfall on that same day and in the previous 1 days. Expression of landslide threshold in the rainfall-induced region of Wanxiu district:Based on the SPSS calculation grouping and purpose of the research, the correction coefficient in the regression model is 2.5 and the expression of the landslide probability of occurrence of the 2-day rainfall is:Exactness is 79% based on the landslide occurring in the history in the research area...