Study On Evolution Features About Loess Slope Of Heifangtai

Development feature,spatial distribution feature and evolution feature of the deformation and failure about loess slope of Heifangtai which is treated as a study object are studied based on analysis of field geological condition,geological evolution process and numeral calculation.The main conclusions are as follows.(1)There are 9 types of slope structure in the study area,and each one has its own structure and distribution characteristics.(2)We know from the slope structure effect under the natural condition the deformation and failure modes of consequent-interface slopes are different from the ones of reverse-interface slopes,and the former slopes are more prone to deformation;Consequent-interface slope is likely to form a loess interface landslide under the condition of bedrock stability.We know from the effect under properties changing that changes accelerate the deformation and failure of slope.From the contrast between the two conditions,we can know consequent-interface slope is likely to be cut out from the top surface of bedrock(or pebble layer),but it is likely to be cut out from the top surface of silty clay layer when loess is saturation.(3)The types of loess landslide can be recognized as loess landslide,loess(bedrock)interface landslide,loess(silty clay)interface landslide,loess-rock incising landslide and loess-rock bedding landslide;The cracks in the plateau can be recognized as unloading crack,traction tension crack and collapse crack.Collapses can be recognized as loess collapse,loess-silty clay collapse.(4)Spatial distribution features of deformation and failure of slope show cluster,selectivity and orientation,the features of landslide,crack and collapse is typical.(5)The mechanism of loess landslide is creep sliding-tension cracking mode,loess(bedrock)interface landslide is sliding-tension cracking mode and sliding compression-tension cracking-shearing mode,loess(silty clay)interface landslide is sliding compression-plastic flow-tension cracking-shearing mode,loess-rock incising landslide is creep sliding-tension cracking mode,and loess-rock bedding landslide is sliding-tension cracking mode;The evolution mode of loess collapse is tension cracking-toppling and cracking tension-sliding,and loess-silty clay collapse is cracking tension-falling.(6)Slope evolution shows similarity,specificity,inheritance,transformation and geological hazard chains,Yehu valley and Moshi valley are two typical examples.(7)We can get the conclusion that type and position selection,spatial distribution and evolution of deformation and failure of slope in the study area are much association with slope structure,which is confirmed by an example about Yehu valley.