滑坡型泥石流转化机制环剪试验研究

 以四川省达县青宁乡滑坡为研究对象，在查明青宁乡滑坡转化泥石流过程的基础上，利用环剪试验模拟青宁乡滑坡失稳以后滑体长距离滑动剪切的过程，分析在剪切过程中土体的物理力学性质变化。结果显示，滑坡型泥石流的转化，除了目前国际上普遍关注的超孔隙水压力的作用外，软弱基座效应也是重要的转化机制之一。滑体在滑动剪切过程中，滑体的剪缩效应以及颗粒的破碎和分层，使滑体土的体积减小，孔隙水压力上升，滑体土的剪切强度降低；同时，滑体的底部形成粉土液化层，且剪切距离越大，黏质粉土液化层的厚度越大，托着滑体快速向前滑动，大大降低了滑体的整体稳定性，该效应为软弱基座效应。

STUDY OF TRANSFORM MECHANISM OF LANDSLIDE-DEBRIS FLOW WITH RING SHEAR TEST

Taking the Qingning landslide in Sichuan Province for an example,its transform mechanism of landslide-debris flow has been studied. After mastering its transform course,longly sliding and shearing course of slide body after its instability are simulated with ring shear test;the physico-mechanical characters during shearing course are monitored. The result shows that the soft base effect is an important factor for transform of landslide- debris flow besides excess pore water pressure,which is the focus of reseach at present. Because of shearing shrinkage,grain crushing and layering,the sliding body volume of soil reduces in the course of shearing,which makes excess pore water pressure increase,and thus its shear strength decreases. Simultaneously,a thick liquefied layer has been formed at the bottom of sliding body,of which thickness increases with shearing displacement increasing. The liqueafied layer carries sliding body moving fast and reduces its stability greatly,which is called"soft base"effect in this paper.