黑方台黄土斜坡变形破坏机理研究

黑方台常年农业灌溉引起地下水位上升，在透水性差的粉质黏土层顶部形成了厚度不断增大的饱和黄土软弱带，导致斜坡蠕动变形诱发了大量的黄土滑坡，滑坡体在地下水的浸润作用下转化为黄土泥流向前运动。为对黄土斜坡的变形破坏机理进行分析研究，进行了8个围压下的固结不排水试验。试验结果表明:饱和黄土应力应变模式表现为强烈的应变软化剪缩型，并具有一定的稳态特性。300 kPa围压以下，试样强度丧失，土体完全液化，其余围压下的试样产生部分液化，抵抗变形能力增加，土体应力状态可划分为完全液化区和部分液化区。斜坡的变形破坏特征因上覆黄土厚度不同而有所差异，通过插值计算，黄土层厚度大于临界黄土厚度（约20 m）时，斜坡产生突发性滑动变形破坏，反之斜坡产生缓慢变形的黄土泥流。研究结果证明了黑方台削方减载治理工程的科学性，并为滑坡的防治和治理提供了一定的理论依据。

A study of the deformation and failure mechanism of the Heifangtai loess slope

Long-term irrigation in agriculture in the Heifangtai area leads to the elevation of groundwater levels. At top of the poor-permeability silty clay layer, the thickness of saturated loess increases. Slope creep deformation induces a large number of loess landslides. Under the action of groundwater infiltration, landslide transforms the loess flow and moves ahead. To examine the deformation and failure mechanism of the loess slope, the stress path tests is designed under 8 kinds of confining pressures. The results show that the stress and strain mode of the saturated loess are in a strong strain-softening way and are of steady characteristics. The strength of samples totally loses and the loess fully liquefies under the confining pressure of less than 300 kPa, and the rest of the samples is partial liquefaction and the ability to resist deformation increases. The soil stress state can be divided into completely liquefied area and part of the liquefaction area. Deformation and failure characteristics of the slope are different because of the thickness of loess. In the interpolation calculation, when the thickness of loess is greater than the critical thickness (20 m), the slope behaves the sudden destruction. On the contrary, loess flow on the type of loess mud flow occurs in the slope. The results show that the reduce-loading is scientific in the Heifangtai area. The research results provide a theoretical basis for prevention engineering of landslides.