黄土边坡的室内模型试验及数值模拟分析

发布时间：2018-12-11 21:22

【摘要】：黄土在我国广泛分布，黄土滑坡问题严重。近年来，对滑坡灾害的研究和治理日益引起人们的重视，，但由于黄土特殊的结构性和力学特性，导致对滑坡内在机理的研究具有很大的难度。为了对黄土滑坡内在规律有进一步的了解，本文以杨凌黄土为研究对象，进行了黄土边坡室内模型试验，探索边坡在人工降雨作用下的渐进破坏规律。同时利用FLAC3D分析了边坡在不同含水率和雨水入渗不同深度下，边坡变形发展、剪切滑移和失稳渐进破坏过程，最后分析了边坡在坡顶加载条件下的渐进破坏过程，本文取得的主要结论如下：（1）在降雨初期，水分平均入渗率为86%，之后随着地表径流增加，入渗速率降低，最后维持在40%左右。在整个过程中，土体的渗透能力逐渐降低，边坡某些区域土体达到饱和状态。（2）在降雨作用下，边坡开始会产生坡面冲蚀和水土流失，并出现许多张拉裂缝和冲蚀沟，当这些裂缝在坡体内部相互贯通时，潜在滑动面形成，随后雨水进一步入渗就会产生较大规模崩滑，滑动区为坡面以下0~1.6m之间。（3）边坡内部只有含水率变化较大的区域，土体运动才最剧烈，这说明水分对边坡失稳有很大的影响。含水率增加致使土体有效应力降低以及导致水分向坡外的渗透力增加，从而使边坡不稳定。 (4)在降雨入渗致使土体含水率变化条件下，随着边坡均布含水率的增加，坡脚的局部开始出现应变局部化现象；当边坡含水率达到一定值时，剪切带从坡脚开始出现，随着含水率继续增加，剪切带逐步发展，当边坡湿度上升到一定程度时后，剪切带贯通，边坡开始滑动。（5）在雨水不同入渗深度条件下，随着入渗深度的增加，边坡经历3个阶段。第一阶段，边坡表层土体迅速失稳，但边坡整体稳定；第二阶段，雨水进一步入渗，致使坡体内部开始出现塑性区和表面裂缝，坡体稳定性开始大幅下降；第三阶段，雨水入渗到坡体内部，致使裂缝和塑性区贯通，剪切带从坡脚到坡顶贯通，边坡失稳破坏。（6）边坡破坏时坡体明显的分为滑动体和稳定体两部分，它们之间具有明显的位移梯度差值。同时，滑动体上各点的运动既有土体本身的变形运动也有滑动体的滑动，并且土体本身的变形运动远大于滑动体整体的滑动。
[Abstract]:Loess is widely distributed in China, and the problem of loess landslide is serious. In recent years, people pay more and more attention to the study and management of landslide disasters, but because of the special structural and mechanical characteristics of loess, it is very difficult to study the inherent mechanism of landslide. In order to further understand the inherent law of loess landslide, this paper takes Yang Ling loess as the research object, carries on the loess slope indoor model test, explores the slope progressive failure law under the action of artificial rainfall. At the same time, FLAC3D is used to analyze the process of slope deformation development, shear slip and instability progressive failure under different water content and Rain Water infiltration depth. Finally, the progressive failure process of slope under the condition of top loading is analyzed. The main conclusions obtained in this paper are as follows: (1) at the beginning of rainfall, the average water infiltration rate is 86%, then with the increase of surface runoff, the infiltration rate decreases, and the infiltration rate is maintained at about 40%. In the whole process, the permeability of soil decreases gradually, and the soil reaches saturation state in some areas of slope. (2) under the action of rainfall, the slope begins to produce erosion and soil erosion on the slope, and many tensile cracks and erosion ditches appear. When these cracks are connected with each other in the body of the slope, the potential sliding surface is formed. Further infiltration by Rain Water will result in a large scale collapse and slip, and the sliding area is between 0 ~ 1.6 m below the slope surface. (3) in the slope, the movement of soil is the strongest only in the area where the moisture content changes greatly, which indicates that the moisture has a great influence on the instability of the slope. The increase of moisture content decreases the effective stress of soil and increases the permeability of the soil outside the slope, which makes the slope unstable. (4) under the condition that the soil moisture content changes due to rainfall infiltration, the strain localization begins to occur at the foot of the slope with the increase of the average moisture content of the slope; When the water content of the slope reaches a certain value, the shear zone begins to appear at the foot of the slope. With the increase of the moisture content, the shear zone develops gradually. When the humidity of the slope reaches a certain degree, the shear zone passes through and the slope begins to slide. (5) under the condition of different infiltration depth of Rain Water, the slope goes through three stages with the increase of infiltration depth. In the first stage, the surface soil of the slope is rapidly unstable, but the slope is stable as a whole, in the second stage, Rain Water further infiltrates, causing the plastic zone and surface cracks in the slope body to begin to appear, and the stability of the slope body begins to decline substantially. In the third stage, Rain Water infiltrates into the body of the slope, which leads to the fracture and plastic zone through, the shear zone from the foot of the slope to the top of the slope, and the slope is unstable and destroyed. (6) during slope failure, the slope body is obviously divided into two parts: sliding body and stable body, and the difference of displacement gradient between them is obvious. At the same time, the movement of each point on the sliding body is not only the deformation motion of the soil itself but also the sliding movement of the sliding body, and the deformation motion of the soil itself is much larger than that of the whole sliding body.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU411

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