中文摘要：

不同侵蚀条件下崩积体的侵蚀产沙特性是阐明崩积体侵蚀机理的关键。采用人工模拟降雨试验,研究不同坡度和雨强条件下崩积体坡面侵蚀泥沙颗粒的变化特征。结果表明：随着雨强和坡度的增大,泥沙粗颗粒含量及粗颗粒的富集率均增加;侵蚀物质随降雨过程逐渐变粗,后趋于稳定,大雨强条件下细沟侵蚀阶段表现为对供试土壤的＂整体搬运＂;侵蚀泥沙颗粒的平均重量直径（Mean weight diameter,MWD）随雨强的增大而增大,1.00 mm min-1和1.33 mm min-1雨强下,细沟间及细沟侵蚀泥沙的MWD随坡度变化均存在临界坡度（30°-35°之间）,其他雨强条件下则无此种情况;雨强对侵蚀泥沙MWD的影响大于坡度。

英文摘要：

A particular type of gully erosion with a steep collapsing wall,locally called＂Benggang＂,is widely distributed in the granite-covered areas of tropical and subtropical South China. These gullies develop fast and erupt suddenly,cause great damage. ＂Benggang＂is generally composed of upper catchment,collapsing wall,colluvial deposit,scour channel,gully mouth,and alluvial fan. Colluvial deposits are materials accumulated at the foot of the collapsing wall.They were originally part of the collapsing wall and surface of mountain slopes and fell apart under hydraulic pressure and gravity. As a type of disturbed soil,colluvial deposits feature high contents of gravel,sand,and loose materials,so that they are often weak in structure,low in cohesion,poor in stability steep in slope（ generally varying between 20° and 40°）and high in erodibility. Furthermore,rainfall splash erosion and runoff scouring erosion occur easily because in addition to the above listed properties,they lack vegetation cover and organic matter. As a result,erosion of colluvial deposits triggers redistribution of materials from the collapsing walls,generating large volumes of sediments,which in turn aggravate the harm of Benggang. Particle size composition of sediment is an important factor of soil erosion. The study on peculiarity of erosion sediment will be of great significance to illustration of mechanism of the erosion on slopes of colluvial deposits.However,so far few reports are available on erosion of colluvial deposits. To study properties of erosion sediment from colluvial deposits,rainfalls were artificially simulated,with intensity ranging between 1. 00 and 2. 33 mm min- 1over a plot 5m2（ 5 m ×1 m） in area and 20° ～40°in slope. Results show the following：（ 1） Changes in sediment particle size composition and enrichment rate： As fine particles are washed preferentially by rainfall,after each rainfall event,the mean enrichment rates of clay,fine silt,course silt,and fine sand are all higher than 1; With rising r