Check the Soil Yield Stress in Situations with different Slope on a Hill Slope with Pasture Cover with the Occurrence Sulification Erosion

One of the most important types of water erosion, is massive erosion. Soils with fine particles (especially silt particles) have little stability against erosion, because they have more water holding capacity and thus increase the saturation moisture and the likelihood of this type of erosion. So In this study, to investigate the relationship between particle size of silt, with behavior and rheological properties of soil in the rabor region of Kerman province, three profiles were studied respectively, at the top of the slope, middle slope and down hill slope. After identifying the soil layers, soil sampling was conducted at various depths. Then some physical and chemical characteristics of the soil, Includes equivalent calcium carbonate, sand, clay, silt, silt components, saturated moisture content and psychological limits was measured in triplicates. The rheological tests such as yield stress and viscosity were also performed to determine the flow behavior of the soil. The results showed that in the study area are high erodibility index position of the bottom and top of hill slope (k=0/54 down the slope and k=0/52 above the slope. The soil profile at the top of hill slope had the highest amount of coarse (28.33%) and saturation moisture (57.29%) and the lowest amount of clay (16.45%). Subsequently it had shear stress much lower than the position of the tilt tolerance and thus faster flow decreases. The shear stress was much lower than the position of the tilt tolerance. The best model to predict the flow behavior of soil was herschel-bulkley model, which has a higher coefficient of determination (R2>0.90) and lower SD than the Bingham and Kasson models. The results also showed that all samples have thixotropic behavior. The fine silt and calcium carbonate equivalent affected behavior and thixotropic properties. The fine silt mostly influnced the shear stress while the calcium carbonate equivalent affected the recovery process structure, viscosity and yield stress and yield stress was a good criterion for predicting soil behavior against sulification erosion and identifying the critical points of this erosion.