植物对陕北黄土边坡稳定性的影响

发布时间：2018-08-17 19:07

【摘要】：近几年来,陕北延安市大力开展治沟造地工程。在工程实施过程中,开挖形成了大量裸露的黄土边坡,存在如滑坡及坍塌等安全隐患。为防护黄土边坡,修复生态环境,采用植物护坡是一种行之有效的措施。本文针对陕北治沟造地工程中开挖边坡的稳定问题,采用现场实地调查、黄土的物理试验、根土复合体的抗剪试验以及FLAC3D强度折减法数值模拟的方法,对陕北黄土的物理性质、影响边坡稳定的因素和破坏机理、植物固土护坡原理以及紫穗槐根系的加固作用进行研究,为治沟造地工程中黄土边坡的开挖以及植物防护的工程实践提供技术支撑。本文的主要研究工作及研究成果如下:(1)对延安治沟造地工程进行实地调查,陕北延安地貌以黄土丘陵沟壑为主,降雨集中。治沟造地工程建设过程中,开挖产生大量的裸露的黄土边坡,分为无台阶开挖边坡、台阶型开挖边坡和直立型开挖边坡。这些裸露的黄土边坡极易受自然风化、降雨等因素的影响,产生坡面剥落、冲刷破坏、湿陷变形,甚至发生崩塌和滑坡。(2)对黄土物理力学性质进行研究,通过在现场取样和土工试验,得到黄土的密度、含水率、比重、液塑限、颗粒级配和抗剪强度指标。延安治沟造地开挖边坡黄土层以中更新统离石黄土(Q2)为主,在小型边坡或者高边坡上部覆盖着上更新统马兰黄土(Q3)。(3)使用FLAC3D软件强度折减法对不同黄土边坡的稳定性进行数值模拟,分析了边坡的高度、坡度、平台宽度,黄土的粘聚力、内摩擦角对边坡稳定的影响以及变形破坏机理。(4)通过对紫穗槐根土复合土体进行直接剪切试验研究以及紫穗槐防护黄土边坡的数值计算分析,得出以下结论:根土复合土体的抗剪强度符合库仑定律,并随着含水率的增加而减小,随含根量的增加而增大;根土复合土体的粘聚力和内摩擦角都随着含根量的增加而增大,附加粘聚力增量较大,内摩擦角增量较小。含水率越大,附加粘聚力和内摩擦角增量越小,但根系的加筋作用随含水率的上升而增强。紫穗槐根系能够提高黄土边坡的稳定性,加筋作用主要作用于含根量大的表层土,对深层土体的加固作用有限。
[Abstract]:In recent years, Yanan City, North Shaanxi vigorously developed ditch construction project. In the process of engineering implementation, a large number of exposed loess slopes have been formed, which have hidden dangers such as landslides and collapses. In order to protect loess slope and restore ecological environment, plant slope protection is an effective measure. Aiming at the stability of excavated slope in Northern Shaanxi Zhigou Land Reclamation Project, the physical properties of loess in northern Shaanxi are studied by field investigation, physical test of loess, shear test of root soil complex and numerical simulation of FLAC3D strength reduction method. The factors affecting slope stability and failure mechanism, the principle of plant soil fixation and slope protection, and the reinforcement of Amorpha fruticosa root system were studied, which provided technical support for the excavation of loess slope and the engineering practice of plant protection in gully reclamation project. The main work and results of this paper are as follows: (1) A field investigation was carried out on Yanan Zhigou land construction project. The landforms of Yanan in northern Shaanxi were mainly loess hills and gullies with concentrated rainfall. During the construction of trench reclamation project, a large number of exposed loess slopes are produced by excavation, which can be divided into three types: no bench excavation slope, step excavation slope and vertical excavation slope. These exposed loess slopes are easily affected by natural weathering, rainfall and other factors, resulting in surface spalling, erosion, collapse, even collapse and landslide. (2) the physical and mechanical properties of loess are studied. The density, moisture content, specific gravity, liquid-plastic limit, particle gradation and shear strength index of loess were obtained by field sampling and geotechnical test. The loess layer of Yanan Zhigou slope is dominated by middle Pleistocene Lishi loess (Q2). The upper Pleistocene Ma Lan loess (Q3). (3) is used to simulate the stability of different loess slopes by using FLAC3D software strength reduction method in the upper part of small slope or high slope. The slope height, slope degree, platform width and cohesion of loess are analyzed. The influence of internal friction angle on slope stability and the mechanism of deformation and failure. (4) through the direct shear test of Amorpha fruticosa root soil composite soil and the numerical calculation and analysis of Amorpha fruticosa protected loess slope, The following conclusions are drawn: the shear strength of the composite soil obeys Coulomb's law, and decreases with the increase of water content and increases with the increase of root content, and the cohesive force and internal friction angle of the composite soil increase with the increase of root content. The increment of additional cohesive force is larger and the increment of internal friction angle is smaller. The higher the moisture content, the smaller the increment of additional cohesion and internal friction angle, but the reinforcement effect of root increased with the increase of moisture content. The root system of Amorpha fruticosa can improve the stability of loess slope, and the reinforcement effect is mainly on the surface soil with large root content, and the reinforcement effect on the deep soil is limited.
【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】：2017
【分类号】：TU444;Q948

【参考文献】