【作者】 陈新建；

【导师】 赵法锁；

【作者基本信息】 长安大学 ， 地质工程， 2013， 博士

【摘要】 黄土在其形成过程中和地质历史时期，发育了大量不同成因、不同形态性状、不同尺度规模、不同力学性质和不同时期的节理、裂隙等，代表着黄土的破损特征。这些破损面扩展、贯通，不仅破坏黄土体的整体性，还成为雨水等的快速入渗通道。同时黄土又具有水敏性。系统总结了黄土滑坡的工程分类，提出黄土滑坡的新类型，即滑动面位于吴起古湖湖相沉积的粉质粘土层，该层粘性颗粒多于上覆黄土，而砂粒多于下伏红粘土，具有较好的滞水层效应和适宜滑动的岩性特征，控制大型（巨型）黄土滑坡。通过颗粒分析，揭示黄土颗粒中粉粒含量占绝对优势，砂粒和粘粒含量基本相当。结合钻孔资料和土工试验，分析了黄土层内部的物理性质随深度的变化规律。野外调查结合现场原位试验、室内直剪试验、环剪试验，分析了黄土剪切滑动时以滑动擦痕为代表的宏观剪切特征。借助电镜扫描，分析了黄土剪切时土粒滑移、拉长、削平为代表的微观剪切特征。试验结果说明残余剪切强度普遍低于原始剪切强度，而饱和后的剪切强度大大低于天然抗剪强度值，足见水对黄土强度的影响很大。不同深度处的或不同含水量的黄土具有不同的剪切行为特性。以岩土破损力学为基础，比较黄土的二元介质模型、结构性土抗剪强度、非饱和黄土抗剪强度，认为黄土的抗剪强度可以表示为三部分：结构体粘聚强度、结构体摩擦强度和结构带摩擦强度。结构块从边缘损伤开始，逐渐向内破损，结构块破损后演变为结构带，结构带扩展、连通、贯通后形成剪切面（带）；雨水等渗入破损面，应力应变在彼此“消长”过程中体现了黄土剪切破损特征。提出破损黄土概念，建立了黄土剪切破损地质模型，分析了局部强度弱化型黄土剪切破坏和局部应力集中型黄土剪切破坏两种类型的剪切破损黄土滑坡的形成机理。运用FLAC模拟了代表第一类滑坡的大台滑坡和代表第二类的大路沟滑坡，分析了形成机理和滑动过程。黄土滑坡是黄土破损特性和水敏性的共同作用、相互促进的结果。更多还原

【Abstract】 The Loess Plateau is an important area for human activities. There are a lot of different formations,different sizes, different shapes, different scales, different periods and different mechanical properties ofjoints, cracks, etc, in Loess, which are on behalf of breakage characteristics of loess. Not only it breakedthe wholeness soil mass, but also became it a fast track for water. At the same time,water sensitivitydamages the loess and loess landslide caused by the water and the breakages.It is comprehensively reviewed the engineering classifications of Loess landslide. Then a new type ofloess landslide is proposed. The slip surface of the new type of landslide is situated among the siltyclaydeposited in the ancient Lake in Wuqi conty. The clay content of the siltyclay is more than that of theoverlying loess. But the sand content of the siltyclay is more than that of red clay. All of these propertiesbring to better water aquitard and apt to slide. What is more to the point, the layer of the deposited siltyclaycontrols most large loess landslides in Wuqi area.By grading analysis of the loess sample, it is revealed that silty contents are dominated. But thecontents of the sand grains are similar to the clay contents. Combining with borehole data and geotechnicaltests, it is analyzed of variation of physical properties of the loess layer with depth.Combining Field survey with in-situ testing and laboratory direct shear test, ring shear test, themacroscopic characteristics of shearing loess are analyzed, such as surface scratches. On the other hand,micro-characteristics of shearing loess are analyzed by making use of electron microscopy scanning. Thetest results indicate the residual shear strength of shear strength is lower than the nature one. And thesaturated shear strength shear strength value is much lower than natural demonstration of water a largeinfluence on the strength of loess. Among different depths, different shear behaviors of loess with differentwater content are attributed.Based on the breakage mechanics, advanced by Shen Zhujiang, comparing binary medium model forloess, structural soil shear strength and shear strength of unsaturated loess, the loess shear strength can berepresented as three parts: the cohesion strength of the bonded blocks, the friction strength of the bondedblocks, and friction strength of weakened bands. The bonded blocks are damaged from the edge to theinner. Finally they are broken to be weakened bands, and the weakened bands are extended to be somebreakage surfaces. Adjustment of stress and strain illustrates the characteristics of loess shearing damage. The concept of breakage loess is advanced. Furthermore, a shearing geological model of breakage loess isestablished. Therefore two types of shear breakage mechanism of loess landslide, part-weakening ofshearing strength and part-concentrating of shearing stress, are advanced to analyze shearing failure ofLoess slope. At last, they are simulated by FLAC.As a conclusion, breakage characteristics and water sensitivity of loess are interaction and mutualpromotion. They may be the main factors to cause loess landslide.更多还原