| Granite collapsing hill was the most seriously soil erosion in southern China. Soil moisture is the power and premise of collapsing hill. In this study, we selected soil of collapsing hill in southern granite as research object. Field survey and monitoring and using hyetometer and soil moisture monitoring system were used. This article analyzed the soil layers’ response mechanism to rainfall and its profile water characteristic. Results showed that:(1) The water content of different soil layers were influenced by rainfall amount and its duration and its intensity. The response of soil moisture to rainfall in each soil layer was pushed back, and every 0.1m was late 2 hours.(2) According to the soil dehydration process, we found that the time of soil moisture loss was longer than absorption. The loss rate of red soil water was significantly higher than sand layer and detritus layer. The rainfall is greater, and the soil moisture removed faster. The soil desorption rate of 1 Ocm was fast.(3) Red soil layer preferential flow phenomenon was obvious, the average dyeing area ratio of red soil layer was small and dyeing profiles were like strip, and dyeing area of red soil layer gradually decreased with depth; The average dyeing area ratio of sand soil layer and detritus soil layer were bigger, which dyeing profiles were like block and the increase of the depth were gradually decline before falling fast. After 24 hours of dyeing experiments, the moisture of 0-9cm sand soil layer and 0-13cm detritus soil layer changed obviously.(4) The moisture migration rate of red soil was the fastest, the second was sand layer and detritus soil layer. The change of moisture movement within 0.2m was more obvious, and the soil water-holding capacity and permeability was low, in the rain vigorous areas, swell soil produce cracks, surface soil after water absorption and dehydration process produce larger cracks, leading to the occurrence of collapse. |
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