| Minjiang river from Wenchuan to Songpan is located in the northwestern part of the Sichuan Basin.The valley is deep and the middle-high mountain landform is dominant.There are many fault zones in the area.The rock mass is broken and the quality is poor.All kinds of geological disasters occur frequently.Therefore,the investigation of large-scale landslide geological disasters in the study area and zoning of regional hazards have extremely important guiding significance for protecting the lives and property of local people and the development and utilization of urban construction.The paper relies on high-precision elevation data,combined with the field investigation,on the basis of previous studies,the paper deepens the analysis of the development characteristics and distribution law of large-scale landslides in the study area.And uses PFC numerical simulation software to select typical landslides and analyze their movements.The process,using Arcgis,SPSS software to establish Logistic model and CF model to evaluate and zoning the geological hazard of large-scale landslides in the study area,and finally reached the following conclusions:(1)The study area is complex in structure,and the river valleys are mostly“V”type.The strata are dominated by phyllite.(2)There are 161 large-sacle landslides(more than 1 million m~3)in the study area,including 83 large landslides,71 huge landslides and 7 giant landslides.(3)The large-scale landslides in the study area are linearly distributed along rivers and fault zones,and the number and scale of development of different river sections and different shore landslides are uneven.According to the coupling degree of water system,fault zone and bank slope structure,the research can be divided into the following five sections:Chuanzhusi-Zhenjiangguan reach,Zhenjiangguan-Diexi reach,Diexi-Lianghekou reach,Lianghekou-Maoxian reach,Maoxian-Caopo reach.Among them,the landslides in the Diexi-Lianghekou reach are the most dense,and the landslide density is 1.13/km.(4)The shape of large landslides in the study area is dominated by sag,which can be divided into three types:complete disintegration landslides,incompletely disintegrated bedrocks in the accumulation body,and mixed accumulation of various types of gravel soils.The landslide is mostly developed in the soft and hard phase formation,and the scale and number of the left bank landslide are larger than the right bank.The number of large landslides is exponentially related to the distance from the fault zone.(5)Two landslides in Xinmo Village were selected as typical landslides in the study area.Using PFC numerical simulation software to analyze the new landslide movement process,the maximum distance of the new landslide movement is 2549m,the maximum speed is 81.35m/s,and the exercise time is about 125s.The old landslide is directly caused by the earthquake and destroyed in a wedge shape.The new landslide is the multi-stage earthquake and gravity.The crack at the trailing edge of the slope is expanded and the lower part of the sliding body is“locked”.The concentration is intensified until brittle failure occurs.During the sliding process,the sliding body gradually disintegrates into debris along the structural surface to form a high-speed remote debris flow.(6)The Logistic model and the CF model are superimposed on the risk area of the study area.The results show that:The factor that has the greatest impact on the risk of large landslides in the study area is the distance between the fault and the landslide.The extremely low-risk areas and extremely low-risk areas in the study area are mainly distributed in the lower area of Caopo Township and above the town of Zhenjiangguan Township.The medium danger zone is mainly distributed in the middle of each branch slope.The extremely high-risk areas and high-risk areas are mainly distributed in the Wenchuan-Maoxian-Diexi-Songpinggou reach,and obvious band-like distribution can be seen along each fault zone.The left bank of the river is more dangerous than the right bank. |
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