| The China ’s Loess Plateau has complex geological structures,frequent seismic activity,and multiple strong earthquakes in history.Geological disasters such as collapses and landslides induced by strong earthquakes have brought huge casualties and property losses to the earthquake area.Different loess slopes have different levels of danger under the action of earthquakes of different intensities,and rapid evaluation is needed in the assessment of earthquake geological disasters and earthquake emergency work.This paper takes loess landslides induced by the 1920 Haiyuan earthquake as the research object.Based on the statistical analysis of the distribution law,development characteristics,failure form and sliding mechanism of the loess earthquake landslides,a set of rapid assessment methods for the earthquake hazard degree of loess slopes is established.The work in this paper has important theoretical significance and engineering application value for the evaluation of seismic safety and seismic geological disasters and the rapid assessment of seismic stability of loess slopes.The main work and research results are summarized as follows:1.On the basis of the existing data,summarize the basic situation and damage loss of the Haiyuan earthquake,summarize the geological environment background of the study area from the aspects of topography,hydrology and meteorological conditions,formation lithology,geological structure and earthquakes The analysis summarizes the relationship between the geological conditions in the study area and the earthquake-induced landslides in the Loess Plateau,which provides the seismic and geological background for determining and extracting the assessmentelements.2.Based on the investigation of the landslide disaster in the Haiyuan earthquake,the basic characteristics of the development and distribution of the loess landslide in the Haiyuan earthquake were statistically analyzed.The rock and soil composition of the landslide body and the development position of the landslide were counted,and the landslide was divided into three types: landslide in the loess layer,loess-bedrock contact surface landslide,loess-bedrock landslide.The inner landslide is the main one.The geometric characteristics of the landslides in the study area are summarized,and the landslide shapes are divided into seven types: semicircle,triangle,horseshoe,strip,rectangle,missing side wall and irregular shape.The failure form and development mechanism of the landslide in the study area were analyzed,and the landslide was divided into four types: vibration cracking type,vibration shearing type,vibration liquefaction type and composite type.Based on the summary of previous research results,the landslide was statistically analyzed from the aspects of landslide length,width,thickness,aspect and main sliding direction,original slope height,original slope angle,and landslide area,volume and intensity division.The development characteristics and distribution rules of the ions provide a field investigation basis for determining the influencing factors of the earthquake hazard degree of the loess slope.3.The concept of the degree of danger of loess slopes was determined and discussed.On this basis,based on the analysis results of the field survey data of landslides,this paper selected four main influencing factors of slope height,slope angle,cover soil thickness and seismic intensity,using numerical values The calculation method determines the weight of each influencing factor,and is based on the fuzzy comprehensive judgment method for rapid evaluation of the earthquake hazard degree of loess slopes.The slope height,slope angle,cover soil thickness and seismic intensity selected in this paper usually do not need to invest a lot of investigation methods,and can be based on existing topographic maps,satellite image data,Quaternary isoline maps and ground motion parameters The zoning map and other materials are quickly obtained,and this earthquake emergency site work provides great convenience.4.Use the evaluation method proposed in this paper to discriminate 156 slopes distributed in the Ⅷ ~ Ⅸ intensity area of ??the Haiyuan earthquake,and use this to verify the effectiveness of the evaluation method.Based on the Geostudiosystem software,the pseudo-static method and dynamic time-history analysis method are used to numerically simulate the typical earthquake slope,and compared with the evaluation results of the degree of danger to further verify the rationality and effectiveness of the evaluation method. |
PDF Full Text Request