Study On Geological Disaster Susceptibility Assessment And Rainfall Threshold In Western Zhejiang Mountainous Area

The terrain in the southwest of Zhejiang is mainly mountainous and hilly,the terrain is undulating,and the fault structure develops.The surface water system in the area is widely distributed,and the rainfall is abundant and concentrated,which provides natural conditions for the development of local disasters.In addition,the concentrated population and frequent engineering activities make the frequent geological disasters in this area,which pose a great threat to the production and life of regional residents.Therefore,it is necessary to analyze the characteristics of geological disasters in southwest Zhejiang,evaluate their susceptibility,and study the rainfall threshold,so as to provide scientific basis for the prevention and control of geological disasters in this region.Taking the north boundary town of Suichang as an example,based on the comprehensive collection of previous geological data,combined with the field investigation,numerical simulation and statistical analysis,the prone occurrence of geological disasters in the north boundary area is analyzed and evaluated,and studies the rainfall threshold of geological disasters.The thesis obtains the following research results:（1）based on the data of geological disasters,the geological information of the north area and field survey results,analyzes the characteristics of the development of disasters in the region,the study disaster with soil slope type,the occurrence time is basically in the plum rain period and the typhoon period,the factors of geological disasters mainly caused by excavation slope engineering activities and rainfall induced,belong to the rainfall type of sudden geological disasters.（2）based on the evaluation factor of the research area slope unit basic information investigation,combined with hierarchical analysis（AHP）and entropy index method（IOE）to survey area of geological disaster prone evaluation,the survey slope unit prone grade divided into low prone,prone and high prone three,basic disasters are located in the medium and high prone.（3）Taking the typical slope in the study area as the prototype,a numerical model is established,based on which the risk coefficient under different rainfall conditions is analyzed.The results show that the risk degree of slope is low in heavy rain and heavy rain,and the risk degree is high in heavy rain and extremely heavy rain.（4）Based on the rainfall data of statistical disaster points,the analysis shows that the impact of rainfall on the disaster is basically within 24h,and then the power function is fitted by Origin,and the preliminary rainfall threshold of geological disaster in Suichang area is I_50%=30D^-0.481.On this basis,the process rainfall threshold of different duration was calculated,and the yellow,orange and red rainfall warning forecast was implemented for the study area.