Study On Physicochemical Characteristics And Erosion Mechanism Of Pisha Sandstone And Integration And Demonstration Of Dual Governance Model In The Middle Reaches Of The Yellow River

The serious soil erosion and fragile ecological environment in the Loess Plateau area,especially the Pisha sandstone area,make the lower reaches of the Yellow River known as the "suspended river" in the world,which poses a great threat to the flood control safety of lower reaches of the Yellow River.In this paper,Huangfuchuan Watershed,the first tributary of the Yellow River in the Pisha sandstone area of Nuanshui town,Jungar banner,is taken as the research area.to carry out vegetation investigation,Pisha sandstone sampling and analysis of nutrient content,physicochemical characteristics,mechanical characteristics,micro morphology,etc.to study the erosion mechanism of Pisha sandstone and the treatment mode of Pisha sandstoneThe results show that the main local vegetation in the area is seabuckthom,caragana,salix,zizyphus.According to the stability of the slope and the characteristics of the rock mass,the main slope types in the area can be divided into 8 units and 24 typical slopes.The grain size of channel sediment is obviously larger than that of slope sediment,and the total nutrient content of Pisha sandstone is very low.The content of feldspar(K-feldspar+plagioclase)is 23%?56%.Under the local bad climate conditions,feldspar is easily weathered,which causes the rock structure to be damaged and the erosion resistance to be weakened.The content of montmorillonite is 5%-28%,which is higher,but the content of white Pisha sandstone is lower than that of other colors.Calcite content is in the range of 1%-25%.Its essence is that under the long-term water erosion,a large number of cracks and pores are produced in the rock mass.Calcite reacts with H2O and CO2 in it,generates soluble Ca(HCO3)2 and dissolves and loses,causing rock damage.Calcite content changes greatly,which is related to the reaction degree of water and CO2.Under the local special natural conditions,the wind erosion of feldspar,the water erosion of calcite,and the water swelling characteristics of montmorillonite make the rock mass completely lose the ability to resist wind erosion and water erosion,thus causing soil erosion.The shear strength of red Pisha sandstone increases first and then decreases with the increase of water content,and the cohesion plays a leading role.The shear strength of white Pisha sandstone decreases with the increase of water content,and the friction and bite force between particles play a leading role.Red and white Pisha sandstones are well graded,but compared with white sandstone,the particle size range of red sandstone is larger.White Pisha sandstone is mainly coarse sand,containing a small amount of fine sand,with obvious angular particles,large pores,strong friction and bite force between particles,and weak cohesion.Red Pisha sandstone has a large amount of fine sand,with dense flocculent structure connection,leading to sliding process.It is dominated by cohesion,and the occlusal friction is weak.This paper puts forward a two-dimensional configuration model which integrates material-engineering-biological measures and slope-top-gully system management.The model includes vegetation measures,consolidation measures,anti erosion measures,gravity erosion measures,runoff efficient utilization measures,silting dam measures,flexible dam measures,etc.The integration and demonstration of this technology is carried out in two tiger ditch,which is on the right bank of Nalinchuan,a tributary of Huangfuchuan river,according to the field observation of runoff area in the area,the sediment yield of the treatment area with anti-corrosion and growth promoting measures is reduced by more than 91%,and the remote sensing pictures show that the area of vegetation area is significantly increased,with good effect.