细粒含量对泥石流斜坡失稳模式与规模的影响

摘要

In order to study the impact of fine particles ( d≤0. 075 mm) of the soil body of debris flow on the inoculation and startup mechanisms of debris flow during the rainfall infiltration and interstitial flow processes, an experiment on slope debris flow induced by artificial rainfall, using a self-made debris flow model tank and an indoor slope model made of three kinds of fine particle soil bodies, was carried out. The experiment studied the formation characteristics of slope runoff, soil erosion characteristics, and slope instability modes of the soil body of debris flow during the rainfall infiltration process. The experimental results show that fine particles of the slope will disperse, drain, and cause coarsening of the surface soil of the slope. The dispersed fine particles of a slope with high fine particle content will migrate to depth, block the holes, and decrease the permeability ( infiltration capacity) of the slope soil, inducing slope runoff and slope failure before the wetting front extends to the lower soil-rock interface, with the failure surface being close to the wetting front ( only a few centimeters away) . The failure mode can be described as sliding-flowing failure of the block at first, and then gully erosion. The scale of soil erosion is related to the rainfall intensity and fine particle content. The failure mode of slope soil with low fine particle content can be described as retrogressive slumping. However, in the experimental process, no massive soil loss occurs, the blockage in the holes of soil with low fine particle content caused by the dispersion and migration of fine particles is not significant, and relatively stable flow with fine particles forms at the soil-rock inter-surface. The fine particle content of the slope soil is important to the slope failure mode and formation of the slope runoff. The security coefficient obtained from the slope stability analysis model considering the impact of the slope runoff shows better agreement with reality.%为了研究泥石流土体的细粒组分( d≤0.075 mm)在降雨入渗和渗流过程中对泥石流孕育与启动机理的影响，利用自制的泥石流模型槽，采用3种细粒含量的土体制作室内斜坡模型，进行了人工降雨诱发斜坡泥石流试验，研究了泥石流土体斜坡在降雨入渗过程中坡面产流的形成特点、水土流失特征以及斜坡失稳模式。试验结果表明：斜坡细粒在雨水入渗过程会发生分散流失而使坡面表层土体粗化；细粒含量较高斜坡中分散的细粒会随雨水入渗向深部运移堵塞孔隙而降低土体的渗透性(入渗容量)，湿润前锋未扩展到下卧土岩界面就发生坡面产流与坡体破坏，且破坏面距湿润前锋较近(仅数厘米)，破坏模式先为块体的滑动流动破坏，然后为沟道侵蚀，土体流失规模与雨强、细粒含量有关；细粒含量较低斜坡的破坏模式为牵引式的滑塌，但试验过程中未发生大规模的土体流失，细粒分散运移作用对低细粒含量土体孔隙的堵塞效应不明显，而在土岩界面处形成了较稳定的携细粒水流。斜坡土体细粒含量对斜坡破坏模式和坡面产流的形成有重要作用，考虑坡面产流影响的斜坡稳定性分析模型得到的安全系数更接近实际情况。