灌溉诱发的黑方台黄土滑坡泥流机理分析

摘要

For a loess flow slide in Heifangtai Gansu Province,field investigation for the geological structure,laboratory tests including basic physical parameters tests,traixial tests,SWCC tests,and finite seep and elasticplastic numerical model are conducted to study the failure mechanism.The changing characters of groundwater table and the related slope stability are analyzed.The yield characteristics associated by comparing the shear stress and shear strength along the slide surface are studied by extracting the stress state along the failure surface.Results show that the flow-slide is a loess landslide,whose failure surface lies in the loess layer.The saturated water content of loess is higher than its liquid limit,meaning the loess is easy to liquefy when it is disturbed;the silt clay below the loess layer has a low saturated permeability and high water storage capacity,making it easy to form a water table above it.Under the irrigation conditions,the ground water table increases slowly,the factor of safety of the slope fluctuates at first and begin to decrease greatly when the groundwater table researches the slide surface.Before irrigation,the shear strength is higher than the shear strength along the slide surface.With the irrigation continuing,the slope toe yields first,and the yield area expands upwards.The following stress redistribution leads to the yield of soil at the crest of slope.At the end the whole soil along the slide surface yields with the stress researches the shear strength.The landslide is a retrogressive landslide.%针对黑方台灌溉触发的黄土滑坡泥流,通过野外测量查明坡体地质结构,室内基本物理力学性质测测试、三轴试验和土水特征曲线的测试等,建立二维有限元渗流模型和弹塑性模型,分析灌溉条件下地下水位的变化特征和坡体的稳定性;并提取滑面上的应力状态分析其剪应力和抗剪强度的变化特点和屈服特征,结果表明该滑坡为纯黄土滑坡,黄土的饱和含水率高于液限,扰动易发生液化;黄土下层的粉质黏土层饱和渗透系数小,储水能力强,易积水形成潜水位.灌溉条件下,地下水位逐渐升高,边坡稳定性开始基本保持不变或缓慢降低,其快速降低始于水位开始接触滑面;灌溉前滑面上的抗剪强度均大于剪应力,随着灌溉进行,坡脚先发生屈服,且范围不断扩大,由于应力重分布作用,滑坡后缘也逐渐发生屈服,最终沿整个滑面上土体的剪应力均达到其抗剪强度.该滑坡为牵引式滑坡.