A Laboratory Study On The Gravitational Erosion Of Loess Gully

The study of gravitational erosion in gully region is of great practical significance for its disaster prevention and mitigation, and sustainable development. This study presents an approach for simulating the gravitational erosion of loess gully that is different from any previously attempted. Firstly, the generalized scheme of loess gully is established, based on the previous laboratory studies, the field investigations of the background region, and the relevant literature. Then a series of model experiments in various initial dimensions are operated to simulate the process of gravitational erosion by the equipment and technology of gully model experiment. Finally, the process of gravitational erosion, the relationship between the gravitational erosion and its influence factors, and the process of the runoff and sediment yield are analyzed. The results can be summarized as follows:(1) This study proposes an observation method, which is suitable for the dynamic and quantitative observation of gravity erosion in gully terrain. The volume of gravity erosion can be quantitatively calculated by the MX-2010-G topography meter according to the topography before and after gravity erosion. Simultaneously, the dynamics of gully can be observed for the whole video recording by the MX-2010-G topography meter.(2) Model experiment method is successfully used to simulate the gravitational erosion of loess gully. According to the model experiment, we conclude that the model experiment and prototype of loess gully are similar, whether the phenomenon of gravitational erosion or the test results.(3) There are many influence factors for the generation of the gravitational erosion. Based on the model experiments, some factors, such as the slope gradient, height and soil moisture of underlying surface and so on, are discussed in this paper. The conclusions are as follows:(a) The slope gradient is the restrictive factor which determines the type and intensity of the gravitational erosion; (b) When the grade are the same, the total volume of collapse and gravity erosion are positively correlated with the height, however the total volume of landslide is less affected by the height; and (c) The soil moisture of underlying surface is the important triggering factor for the occurrence of gravitational erosion, which is basically consistent with the landform development and the process of the gravitational erosion.(4) Combining the gravitational erosion and observation results of the outlet of the models, the process of runoff and sediment yield is researched in this study. The conclusions are as follows:(a) Cumulative runoff is significantly relative to rainfall duration in linearity, while cumulative sediment yield has a power function relationship with rainfall duration; (b) Sediment concentration and sediment transport rates increases with the rainfall duration, and it's more obvious in the late of each rainfall; (c) Gravitational erosion has a positive correlation with sediment concentration, and it also plays an important role in the hyperconcentrated flows.