Spatial Effect Of Weathering Of Paleogene Red Beds In Lanzhou

Red beds are widely distributed in southwest,northwest,South China and central China.Red bed landslides in Western China account for about a quarter of all kinds of landslides.Paleogene and Neogene strata are widely distributed in Lanzhou,The sedimentary age of the red bed is relatively new.The lithology of the red bed rock under the loess layer is weak and the structure is loose.After encountering water,it becomes delicate and smooth,which is easy to develop into a sliding surface.The Gaolanshan landslide group and Jiuzhou landslide group directly affect the life and property safety of the people in Lanzhou City,and also affect the ecological protection and high-quality development of the Yellow River Basin.Based on this,this paper takes the Paleogene red beds in Lanzhou area as the research object,and studies the spatial effect of weathering of Paleogene red beds in Lanzhou by measuring hardness and magnetic susceptibility,physical mechanical test,scanning electron microscope test,XRD test,and analyzing the spatial effect of physical mechanics,microstructure and material composition.The main research contents and achievements are as follows:(1)Spatial effect of physical and mechanical indexes: the impact on particle density is concentrated within 30 cm of the slope surface;the impact on natural density and dry density is mainly concentrated within 20 cm of the slope surface;the impact on rock sample void ratio and porosity is concentrated within 10 cm of the slope surface;With the increase of horizontal depth,the natural water content first increases and then tends to be stable.With the increase of horizontal distance,the hardness value increases first,then tends to be stable;the shear strength index internal friction angle ? and cohesion c increase rapidly with the increase of horizontal distance.(2)Spatial effect of microstructure: when the horizontal distance is small,the rock samples are mainly schistose clastic and granular,and the granular clastic rock fills the void,the structure is loose.With the increase of the horizontal distance,the granular clastic rock decreases,gradually becomes schistose clastic,and the cementation is tight,and the structure is dense;the closer to the slope surface,the apparent void ratio and porosity of the rock mass The larger the number and average pore area,the smaller the degree of homogenization of pores,the narrower the shape of pores,the lower the degree of smoothness,the more complex the pore structure,the weaker the directionality and order in the structural unit,the more chaotic the arrangement of the structural unit,and the stronger the randomness.(3)Spatial effect of material composition: it is found that the stable Si and Al elements are enriched,the migration ability is strong,and Na,Mg,K and Ca are poor.Near the surface of the slope,the active elements Na,Mg,K and Ca are all lost to varying degrees;the mineral composition of the rock sample mainly includes plagioclase,mica,quartz,K-feldspar,calcite,gypsum,montmorillonite,illite,sodium Feldspar and orthoclase;the change of magnetic mineral content is mainly concentrated in the slope surface within 30 cm,in this range,the magnetic susceptibility decreases with the increase of horizontal distance,and the content of magnetic mineral decreases.