Mechanical Stability Of Several Typical Zonal Soil Aggregate And The Rainfall Splash Erosion

Soil erosion is one of the extremely important environmental problems in today’s society,soil and water loss caused by soil erosion not only cause degeneration of the land resource,the runoff sediment and the pollutants attached to them seriously threaten the water environment and ecology.Soil structure is the most important factor to determine the soil erosion resistance ability;aggregate,the basic structure of the soil unit which is also the basic unit of the soil to resist external agent destruction,its mechanical stability characteristics influenced by the composition material and cementing substances of soil.The composition of different soils depends on different hydrothermal conditions and soil parent material which exist zonal distribution,lead to structure characteristics differences of soil and aggregate.In this study,we select a sequence of typical zonal soils in tropical and subtropical like Cinnamon soil,Yellowcinnamon soils,Brownish red soils,Red soils,Latosolic red soils and Latosols as research objects,to investigate the variations of aggregate tensile strength for zonal soils and their stabilization mechanisms.The impact factors which affect the mechanical stability characteristics of the soil and aggregate are the main research content.We made a further study of the relationship between soil mechanical stability and aggregate stability,and their influence on rainfall splash erosion process,which provides a scientific basis for prediction of soil and water conservation.Main work and conclusions are as follows:1)There is obvious structural difference between typical zonal soil aggregate,from north to south,the tensile strength of the aggregate shows a tendency of decrease.The aggregate tensile strength of the same soil decreases gradually along with the increase of aggregate diameter.The silt content of soil,the content of free iron oxide,aluminum and clay mineral content of vermiculite,kaolinite is the main influence factors of soil aggregate tensile strength.Path analysis results show that the clay content,clay mineral in the soil,and the content of Fed and Ald is the direct cause make the zonal soil aggregate tensile strength difference.Multiple stepwise regression showed that the Fed,cation exchange capacity can be used to better evaluate tensile strength of 3-5mm aggregate.2)The index of the soil mechanical stability showed no obvious zonal change law,the cohesive force of surface soil is obvious lower than subsoil.Soil compactness is the main influence factors of penetration resistance and cohesive force,it increases with the increase of soil bulk density and,along with the increase of porosity and organic matter content decreased gradually.The Angle of internal friction of the tested soil and soil mechanical composition,free iron oxide,aluminum,and clay mineral content showed significant correlation,soil of the clay mineral composition and the content of free iron oxide,aluminum is the most important factors affecting soil Angle of internal friction.3)There is a significant correlation between aggregate tensile strength and internal friction angle,with the increase of Angle of internal friction,aggregate tensile strength decreases gradually.Typical correlation analysis showed: 3-5 mm aggregate of tensile strength is the most important factor influencing soil structure characteristics,the cohesive force of the soil are the key factors that affect soil structure.Clay content and clay mineral is the most important factor affect the stability of soil strength.4)We use sieve method and LB method to characterize the water stability of the zonal soil aggregate.With the loss of the latitude,the water stability of aggregate gradually strengthened,dissipate crushing effect is the main factor causing the cohesive soil aggregate crushing.The content of the soil clay,silt,clay mineral and the content of free iron oxide,aluminum zonal soil aggregate is the main factors affecting water stability.There is a close relationship between aggregate mechanical stability and water stability,the two Shared a common material base.Aggregate of the tensile strength and water stability of soil significantly related,the stronger the tensile strength of aggregate,the weaker the water stability.5)Aggregate total splash erosion rate present the obvious zonal distribution,with the loss of the latitude,the total splash erosion rate gradually decreases.Tensile strength of 3-5 mm dry aggregate and total splash erosion rate has reached the extremely significant correlation,the tensile strength,the greater the total splash erosion rate.Combined with the rainfall splash erosion rate change process,we further analysis the relationship between the index of soil aggregate stability and soil splash erosion,water stability of aggregate is involved in each process of rainfall splash erosion,the correlation between aggregate water stability and rainfall splash erosion is stronger,it is more suitable to express the corrosion resistance of the soil than the aggregate mechanical stability.