| The loess is thick and widely distributed on Loess Plateau in China. The drought and semi-drought climate and the special properties of loess result in serious Soil and water loss in the area. Therefore, the geomorphic landscape is usually characterized by gullies, where me gravity erosion such as slide and collapse are very active. Slide erosion, the main resource of gully sediment yield, is one of the most important types of gravity erosion. However, the gravity erosion, of which many aspects still need further research, has been lagged because of various reasons. In mis paper, firstly, with the achievements of many predecessors, based on the analysis of the erosion causes of loess plateaus and the distribution of slide erosion in typical areas by methods of field investigation, numeric analysis and typical cases analysis, the slide erosion analyzing system is tentatively founded which can express the relationship between soil and slop erosion. Secondly, the dynamical mechanics and movement of typical slide erosion body is deeply researched by method of numeric analysis. Finally, the regional slide erosion is quantitatively evaluated by method of information quantity theory. The main achievements are as follows:1. It is put forward mat the definition of slide erosion, the shape elements, classification, catastrophic chain, formation condition, inductive factors, the differences between slide erosion and other gravity erosion are suggested, based on the theories of soil erosion, geology, and geomorphology The geological model to calculate the slide erosion is founded on the basis of many investigation and testskof the litho logic characters and mechanical properties of typical slide, based on which the slide erosion analyzing system is set up.2. The mathematical-mechanical model of slide erosion is founded on the basis of the elastic-plasticity theory. Through the calculation of the network distortion, principal stress, principal strain, shear stress, safety rate and the stress distribution on the fractured surface of the typical slide in Tong-chuan city by finite element method, the mechanical situation of different parts of the typical slide are finally mastered.3. Based on the principals of kinematics, the kinematics model of slide erosion is founded. After the discrete units simulation of the movement of collapsed slide, the duration curves of motion states,moving pathways, the relationship between contact force and angle-edge contact, mean principle stress, mean displacement, force moment and acting force, striking angles, velocity, accelerated velocity of different parts of the sample slide are obtained, as a result, the process of slide movement is divided into five stages, which is a new achievement to the slide erosion process.4. The model of quantitatively evaluating slide erosion is founded according to the information quantity theory. There are many factors that influence slide erosion, which are groundwater on the bedrock surface, thin plant cover, heavy human activity, high gully density, loess and bedrock layers, difference in elevation (which is bigger than 50 meters), degree of slide (between 20?and 40?), degree of slide (which is bigger than 45?), high-accelerate earthquake, groundwater inside the loess slide, of which the formers contribute much more than the laters to slide erosion.5. Field investigation and numeric analysis shows that The total area area of the studied zone in Tong-chuan is 82.5 square kilometers, where slide erosion area is 44.5 square kilometers, occupying 53.9% of the total area; the area without slide erosion is 38.0 square kilometers, occupying 46.1% of the total area; the serious slide erosion area is 13.0 square, occupying 15.76% of the total area; the drastic erosion area is 20.00 square kilometers, occupying 24.24% of the total area; the middle erosion area is 25.25 square kilometers, occupying 30.61% of the total area; the mild erosion area is 6.0 square kilometers, occupying 7.27% of the total area; the weak erosion area is 18.25 squa...
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