Effect Of Straw Mulch To The Prevention And Treatment Of The Colluvial Body Erosion Under Stimulated Rainfalls

Collapsing hill as a serious soil erosion types in the weathered granite area of South China, brought a series of negative effects to the local social economy. Colluvial deposits as an important part of the collapse, with loose soil, the coarse particles content is high, easy to be eroded etc. At present, the way to control and measures collapse colluvium soil erosion are mainly concentrated in the construction of retaining walls, dams and Gu Fangqun and so on, but the straw mulching treatment of colluvial erosion on the body is still blank. In this experiment, we choose Yang Keng, Longmen, Anxi in Fujian Province as the research object, through combining the different slope (25°,30°and 35°), rainfall intensity (60,90 and 120 mm·h-1) and coverage (0,25,50,75 and 100%) under artificial simulation of rainfall to study the processes of runoff and sediment,sediment particle characteristics and dynamic mechanism of water erosion of the colluvialslope collapse erosion, and to explore the mechanism of integrated slope, the results are as follows:(1) In the same rainfall intensity and slope conditions, the initial runoff time extend with the increase of the coverage conditions; at the same time rainfall intensity and coverage, the initial runoff time changed into two situations, in the heavy intensity (90 mm-h"1 and 120 mm·h-1), the initial runoff time shortened with the increase of slope; in the light intensity (60 mm·h-1),the initial runoff time shortened firstly and the increased with the increase of slope. In the same slope and coverage, the initial runoff time shortened with the increase of rainfall.(2) Compared with the light intensity(60,90 mm·h-1), The runoff under the large slope (35°) and heavy (120 mm·h-1) up and down significantly than the low grade (25°and 30°). In the process of rainfall, the runoff rate remained stable with the increase of the coverage, and increased with the increase of rainfall; the sediment transport rate decreased significantly with the increased of coverage and increased with the increase of rainfall; with the increase of slope, the sediment transport rate own a critical coverage of 30°nder the conditions of no coverage, and increasee with the condition of cover. The runoff rate and sediment transport rate have a significantly linear relationship with the slope, rainfall intensity and coverage, the rainfall intensity influenced significantly to the runoff rate,the coverage influenced significantly to the sediment transport rate.(3) In the aspect of sediment particle size, the content of coarse sand and fine silt is high, and the content of gravel, sand, silt and clay is low. High coverage of straw under the slope (25°) and rainoff intensity (60 mm·h-1) can reduce the gravel and coarse sand effectively, but the effect to reduce the grain size of sediment particles under the slope (35°) and rainoff intensity (120 mm·h-1) is small. In the aspect of sediment changed with time, the coarse particles content decreased gradually with the increasing coverage, and reached a very low level eventally. In the aspect of the separation characteristics of sediment, the weight diameter of sediment decreased with increasing coverage.(4) Flow velocity increased slowly with the changes of rainfall time, the flow velocity of straw covered significantly higher than no straw cover. The depth of slope increased with the increase of coverage and rainfall intensity. The Reynolds number increased with the increasing rainfall intensity, and is not relate to the coverage significantly. The Frode number decreased with the increasing coverage, the Frode number of blank slope is higher than the number of coverage significantly.(5) In the slope of 30°, slope sediment rate and the flow velocity and Froude number is positive correlated significantly, negative correlated with depth, and have no relationship with the Reynolds number and resistance coefficient. Flow shear stress and section unit energy increased with the increasing coverage and rainfall intensity. The unit stream power decreased with the increasing coverage, and increased with the increasing rainfall intensity.