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揭示降雨作用下坡面红土起动的影响因素,建立降雨作用下坡面红土起动条件,为深入研究云南红土坡面侵蚀提供参考。根据红土特性,结合降雨作用下坡面红土的侵蚀过程和现象,采用模型试验及力学模型相结合的研究方法。结果表明:(1)降雨作用下坡面红土侵蚀主要呈现溅蚀和结皮2种现象。(2)红土黏聚力对坡面红土颗粒起动有阻碍作用,且抗剪强度越大,坡面红土颗粒起动的临界切应力也越大。降雨及孔隙水压力对坡面红土颗粒起动有促进作用,且雨滴密度与雨滴终速越大,降雨的影响也越大;红土颗粒粒径越大、雨滴直径与水深之比越小,降雨的影响也越小。(3)建立了坡面红土颗粒在联结和松散状态下起动的临界切应力计算公式。降雨作用下坡面红土颗粒起动的临界切应力与红土颗粒粒径大小、抗剪强度以及降雨雨滴特性、坡面径流特性密切相关。松散状态的坡面红土颗粒在降雨作用下只需很小的径流切应力即可起动。
The influencing factors on the onset of lateritic soils under rainfall were revealed. The conditions for starting the lateritic soils under rainfall were established to provide reference for further study on the red soil erosion in Yunnan. According to the characteristics of lateritic clay, the erosion processes and phenomena of laterite red soil under rainfall are studied, and the research methods of model test and mechanical model are used. The results show that: (1) There are two kinds of phenomena of erosion and crusting mainly on the red soil erosion under the rainfall. (2) The cohesion of laterite hinders the starting of the laterite particles on the slope, and the greater the shear strength, the greater the critical shear stress of the laterite particles on the slope. Rainfall and pore water pressure can promote the initiation of laterite particles on the slope, and the greater the raindrop density and raindrop velocity, the greater the impact of rainfall. The larger the particle size of laterite, the smaller the ratio of raindrop diameter to water depth, The impact is less. (3) The critical shear stress formula for starting the laterite particles on the slope is established. Under rainfall, the critical shear stress on the grain size of laterite particles is closely related to the particle size, shear strength, raindrops and runoff characteristics. Loose particles on the slope of the loose state of rainfall under the action of only a small radial shear stress can be started.