灌渠渗漏诱发的黄土滑坡泥流触发机理分析

Analysis of the Triggering Mechanism of a Loess Flowslide Induced by Water Canal Leakage

20世纪70年代以来,中国黄土地区兴建了大量的灌溉系统,以促进农业生产。与此同时,由灌渠渗漏诱发的黄土滑坡也越来越多,并造成巨大的人员伤亡和经济损失。发生于2006年10月6日的陕西华县高楼村滑坡泥流就是由灌渠渗漏引发的。为了弄清楚此类滑坡泥流的触发机理,首先根据非饱和渗流理论,建立了滑坡发生前原始边坡模型模拟灌渠渗漏水分下渗的过程。为了了解边坡变形破坏的应力状态,取滑坡后缘原状黄土试样在饱和状态下进行不同应力路径的三轴试验,分别为模拟水位上升过程中潜在滑面上的应力路径试验和常规加载应力路径试验。结果表明:随着间歇性的渗漏水下渗,边坡内形成上层滞水并不断上升,使边坡内饱和区的孔隙水压力增加,非饱和区基质吸力减小;持续上升的水位引起了边坡土体的初始变形和破坏,土体结构破坏,产生超孔隙水压力;斜坡顶层黄土结构疏松,饱和含水率大于液限,使得饱和黄土由固态瞬间转化为流态,滑坡转化为泥流。

A lot of irrigation systems have been established to promote agricultural production since the 1970 sin the loess area of China.At the same time,the loess landslides increase because of the canal leakage.Gaoloucun landslide,located in Hua county of Shaanxi,China,is one of those landslides.In order to find the initiation mechanism,based on unsaturated permeability theory,a finite element model of the pre-failure slope was established to simulate the process of infiltration induced by water canal leakage.In order to find the stress state of slope failure,the loess samples were collected from the back edge of Gaoloucun landslide,and the triaxial tests of different stress paths under the saturation condition were performed.The triaxial tests include the stress path test on the possible sliding surface in the process of the increase of simulated water level,and the common load stress path test.The results show that because of the intermittent leakage,the perched water forms and rises in the slope,so that the pore water pressure in the saturated area increases,and the matric suction in the unsaturated area decreases;the rise of water level causes the initial deformation and damage,and the excess pore water pressure forms;the structure of loess soil at the top of the slope is loose,and the saturated water content is higher than the liquid limit,so that the saturated loess soil instantaneously changes from solid state to flow state,and the landslide is transformed into flowslide.