Risk Assessment Study Of Landslide Geological Hazards In Zhangjiakou Area

Zhangjiakou is a transportation hub linking Beijing and Tianjin and linking Shanxi and Mongolia.There are many important projects built or being built in the area.In recent years,human engineering activities are frequent,the slope body has been destroyed more and more seriously,and the protection measures are less.In the heavy rainfall,collapse,landslides,debris flow and other geological disasters frequently occur,which seriously threaten the safety of important projects,people's lives and property.Therefore,the study of landslide hazard is of great practical significance.Based on field survey results and indoor test analysis,combined with previous research data,landslide in Zhangjiakou area is taken as the research object.The background,development characteristics and influencing factors of landslide were analyzed,and the basis for the selection of geological hazard risk assessment factors was provided.Based on the FLAC3D numerical simulation software,the formation mechanism of typical landslides in the study area is studied.The composition and different position of the andslide was studied by the XRD diffraction experiment.ten evaluating factors on the geological hazards danger,hazard point density,engineering rock group,annual rainfall,slope gradient,terrain undulating degree,active fault,peak acceleration of ground motion,river and slope direction are selected,and the weight of evaluation factors is calculated by analytic hierarchy process.Using the weighted information model and ARCGIS platform,we evaluated the geological hazard risk of landslides in Zhangjiakou area.The main conclusions are as follows:(1)Through field investigation and indoor statistical analysis,it is found that the scale of landslides in Zhangjiakou is mostly small to medium-sized landslides.The plane shape is mostly tongue shaped and semicircle,and the profile form is mostly staircase,concave and convex.The slope boundary is clearly distinguishable,the rear edge develops pull cracks,and the landslide body develops gully.(2)The landslides in the study area are mostly developed in the area of alluvial deposits,soft-hard rock formations.The landslide is mainly distributed in the height difference range of 20-100m.The density of landslide develop gradually increase with the increase of slope gradient.The density of landslide develop is relatively larger at30-58 degrees,and the density of landslide develop is relatively small when the slope is less than 30 degrees.The landslide disaster is the most likely to occur in the northeast,East,Southeast,southwest and West.With the decrease of the vertical distance from the fault,river and highway,the landslide growth density increases.(3)The stability of the Wanghutai landslide is simulated under natural and rainfall conditions by the FLAC3D numerical simulation software.The results show that the landslide in the natural condition is in a stable state,and the deformation and damage will occur under the rainfall conditions,resulting in landslide instability and the formation of landslides.At the same time,and the contact zone between mudstone and sandstone probably is a slip zone.(4)The main composition of landslide body is quartz,plagioclas,potash feldspar,montmorillonite and illite.Calcite,Baiyun Mountain,chlorite and kaolinite are relatively few.The clay mineral content of mudstone in the study area is obviously higher than the general value,and mudstone is one of the main influencing factors in the landslide formation in this area.The content of clay minerals in different positions of landslide is different.The content of clay minerals in the sliding zone is much higher than that of the sliding bed and slide body.The content of expansive clay minerals is of great importance to the formation of slip zones.(5)The weight of evaluation factors is calculated by the analytic hierarchy process(AHP).The weight values of landslide hazard point density,engineering rock group,annual rainfall,slope gradient,terrain undulation,active fault,peak acceleration of ground motion,highway,water system and slope are 0.252,0.204,0.157,0.118,0.084,0.064,0.045,0.034,0.026 and 0.018 respectively.(6)The risk of landslide in the study area is zoned by the weighted information quantity model and combined with ARCGIS software.It is divided into three levels:high risk area,middle risk area and low risk area.The landslide density in high dangerous zone of landslide hazard is 0.0232/km~2.The high dangerous zone of landslide hazard is 4650km~2,accounting for 12.7%of the total area,and one hundred and eight landslides are developed,accounting for 87.8%of total landslide.The landslide density in medium dangerous zone of landslide hazard is 0.000761/km~2.The medium dangerous zone of landslide hazard is 14500km~2,accounting for 39.4%of the total area,and eleven landslides are developed,accounting for 8.9%of total landslide.The landslide density in low dangerous zone of landslide hazard is 0.000227/km~2.The low dangerous zone of landslide hazard is 17600km~2,accounting for48.0%of the total area,and four landslides are developed,accounting for 3.3%of total landslide.