【摘要】：近幾年來,陜北延安市大力開展治溝造地工程。在工程實施過程中,開挖形成了大量裸露的黃土邊坡,存在如滑坡及坍塌等安全隱患。為防護黃土邊坡,修復(fù)生態(tài)環(huán)境,采用植物護坡是一種行之有效的措施。本文針對陜北治溝造地工程中開挖邊坡的穩(wěn)定問題,采用現(xiàn)場實地調(diào)查、黃土的物理試驗、根土復(fù)合體的抗剪試驗以及FLAC3D強度折減法數(shù)值模擬的方法,對陜北黃土的物理性質(zhì)、影響邊坡穩(wěn)定的因素和破壞機理、植物固土護坡原理以及紫穗槐根系的加固作用進行研究,為治溝造地工程中黃土邊坡的開挖以及植物防護的工程實踐提供技術(shù)支撐。本文的主要研究工作及研究成果如下:(1)對延安治溝造地工程進行實地調(diào)查,陜北延安地貌以黃土丘陵溝壑為主,降雨集中。治溝造地工程建設(shè)過程中,開挖產(chǎn)生大量的裸露的黃土邊坡,分為無臺階開挖邊坡、臺階型開挖邊坡和直立型開挖邊坡。這些裸露的黃土邊坡極易受自然風(fēng)化、降雨等因素的影響,產(chǎn)生坡面剝落、沖刷破壞、濕陷變形,甚至發(fā)生崩塌和滑坡。(2)對黃土物理力學(xué)性質(zhì)進行研究,通過在現(xiàn)場取樣和土工試驗,得到黃土的密度、含水率、比重、液塑限、顆粒級配和抗剪強度指標(biāo)。延安治溝造地開挖邊坡黃土層以中更新統(tǒng)離石黃土(Q2)為主,在小型邊坡或者高邊坡上部覆蓋著上更新統(tǒng)馬蘭黃土(Q3)。(3)使用FLAC3D軟件強度折減法對不同黃土邊坡的穩(wěn)定性進行數(shù)值模擬,分析了邊坡的高度、坡度、平臺寬度,黃土的粘聚力、內(nèi)摩擦角對邊坡穩(wěn)定的影響以及變形破壞機理。(4)通過對紫穗槐根土復(fù)合土體進行直接剪切試驗研究以及紫穗槐防護黃土邊坡的數(shù)值計算分析,得出以下結(jié)論:根土復(fù)合土體的抗剪強度符合庫侖定律,并隨著含水率的增加而減小,隨含根量的增加而增大;根土復(fù)合土體的粘聚力和內(nèi)摩擦角都隨著含根量的增加而增大,附加粘聚力增量較大,內(nèi)摩擦角增量較小。含水率越大,附加粘聚力和內(nèi)摩擦角增量越小,但根系的加筋作用隨含水率的上升而增強。紫穗槐根系能夠提高黃土邊坡的穩(wěn)定性,加筋作用主要作用于含根量大的表層土,對深層土體的加固作用有限。
[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.
【學(xué)位授予單位】：西北農(nóng)林科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU444;Q948

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