Research On The Environmental Factors And Erosive Mechanism Of Collapsing Hill In South China

The Collapsing Hill is a specific form of soil erosion in the red soil region, Southern China. It is one of the most important indications of serious soil erosion. This special geographic phenomenon has long been concern to many scholars, government agencies and the public. The research is needed to further understand the mechanisms causing land crumbling at all micro-level, meso-level and macro-level scales. In the past, research method on collapsing hill is relatively simple and limited, with a narrow perspective, and research topics are too broad and lack details. Because of these limitations, I used a combination of broad field investigation with plot-based detailed representation to study land crumbling-related internal soil structure and erosion mechanisms under a broad environment context.The research finding shows that the physical features, ground types and physiognomy which are established by the geological formation movement have strong influence on the development phases and directional distribution of collapsing hill. Besides, the result of quantitative classification indicates notable characteristics which include secondary, xerophytes and degradation. The shear strength for different soil type varies along the horizontal dimension. In the vertical dimension, the strength is gradually decreasing while the depth is increasing. In each soil layer of granite, there commonly exist veined weak plane which have the direction as the granite joints. This plane has no obvious difference with the surrounding soil but with obvious lower cohesive strength. When the water is washing through the soil, the order of the crumble velocity is showing as the following: Chorizon> Reticulated Mottling Horizon > Red soil horizon. The granite soil contains lower amount of amorphous oxides and free oxides which indicates a certain defect of binding materials in its structure. The cohesive strength of the soil and its clay content as well as the noncrystalline Alumina has favorable positive correlations. The shear resistance coefficient equation is established by those simple indicators.