降雨作用下坡面红土起动条件研究

A Study on the Starting Conditions of Rainfall-affected Laterite Particles on Slopes

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 of laterite starting on slopes under the effects of rainfall were revealed.The starting conditions of laterite starting on slopes under the effects of rainfall were established,in order to provide a reference for further study on slope erosion of laterite in Yunnan.According to the characteristics of laterite and the erosion processes and phenomena on the slope surface,the method of combining the model test and the mechanical model was adopted.The results indicated that：（1）The splash erosion and crust were the two main phenomena in the processes of erosion of laterite on slopes.（2）The cohesive force of laterite could block the starting of laterite particles on slopes.The greater the shear strength,the greater the critical shear stress of the laterite particles.Rainfall and pore water pressure could promote the starting of laterite particles on slopes.The greater the raindrop densityρand the final velocity,the greater the impact of rainfall.When the particle size d was larger and the ratio of raindrop diameter to water depth decreased,the effect of rainfall was smaller.（3）The formulas of the critical starting shear stress of laterite particles in the connection and loose state were established.The critical starting shear stress of laterite particles on slopes was closely related to the particle size,shear strength,rainfall characteristics,and runoff characteristics.Under the effects of rainfall,a small flow shear stress could make the laterite particles under loose state start.