Study On The Erosion Mechanism Of Red Soil Bank Slope Under Rainfall

Taking Yunnan laterite reservoir bank slope as the research object, using the method of artificial rainfall simulation, by setting different rainfall intensity, slope gradient, slope length, different initial water content, dry density, particle composition and other conditions, the rainfall characteristics, topographic characteristics, physical and mechanical properties of clay, slope surface water dynamic characteristics influence on slope surface erosion characteristics are studied, clear the erosion characteristics of laterite reservoir slope under rainfall, analysis by soil mechanics and hydraulics theory, discusse the effect of rainfall slope laterite starting condition, and combined with the experimental study, the erosion mechanism of laterite reservoir bank slope under rainfall is revealed, in order to provide basis for Yunnan laterite bank erosion prediction and prevention.The observations of erosion, runoff and sediment have been showed that the slope sharp rise in moisture content, partial slope to water, there are slope splash erosion phenomenon before runoff. Runoff, the slope runoff collected color has a "shallow and deep and shallow" rule, slope surface crusting phenomena.Slope runoff lead increase rapidly, then gradually stabilized state, and stable production flow rate with the rainfall intensity, the dry density increase.Slope into infiltration rate decrease rapidly, then gradually stabilized state, stable infiltration rate with the dry density decrease, with the increase of rainfall intensity has increased firstly and then decrease.Slope erosion amount of rainfall over time showed a sharp increase in first after decaying trend.Rainfall characteristics, topographical features have a significant impact on the slope. In the test range, slope erosion modulus increase with the intensity of rainfall increase power function, slope erosion modulus with increasing slope length of a quadratic polynomial or an exponential function increase,slope erosion modulus with slope increase increased first decreasing trend, and the critical gradient value exist.The physical and mechanical properties of red soil have important influence on slope erosion. Under different initial conditions, the higher the initial water content, soil clay and Fe and Al oxides, the less the greater the slope erosion modulus, initial dry density and the erosion modulus the relationship is more complex, then decrease trend.The moisture content and dry density have an important impact on the index and its shear strength, so shear strength of laterite between erosion modulus has a certain correlation.The effects of hydrodynamic characteristics on slope erosion show that the runoff shear stress and the erosion modulus linear correlation under the action of rainfall.The runoff shear stress, slope critical shear stress both increase with the increase of dry density of slope.Theoretical study on the starting condition of the red soil particles on the slope have been proved that the slope particles starting critical shear stress has a linear relationship with shear strength of soil erosion state.Slope force comprehensive expression fixed particles, the critical shear stress loose particles available cohesion, friction, and other forces on the move.The microstructure characteristics of slope erosion in the process of rainfall have been showed that the microstructure image become smooth, and the pore ratio decrease, the number of soil particles, the fractal dimension and the orientation of the soil increase.Under the action of rainfall of laterite type reservoir bank slope erosion mechanism is actually a raindrop on the slope particles dissipate, blow, rain on the slope particles softening, lubrication, fine particle migration, mineral ionization hydrolysis, runoff of slope particles peeling action results.