【作者】 嵇晓雷；

【导师】 杨平；

【作者基本信息】 南京林业大学 ， 森林工程， 2013， 博士

【摘要】 植被根系固坡技术作为一门工程技术，已经在边坡防护工程中得到广泛应用，但是目前对其理论研究却滞后于工程实践中的应用。本论文在现有研究资料的基础上，综合应用分形理论、岩土工程边坡理论和植物生态理论，在系统研究摩擦型根土粘合键的破坏机理、植被根的形态模型、根土相互作用机理、力学模型等基础上，考虑复杂群根与土的共同作用，为定量计算植物根系对边坡稳定性提供理论依据和方法，同时通过不同根系形态与土相互作用的机理研究，为模拟植被根系固坡作用的新型人造结构物或加固方法提供理论依据。论文采用野外实地调研与室内试验相结合，试验研究与数值模拟相结合的研究方法，研究了狗牙根和夹竹桃根系的形态分布规律，根据根系形态特征，研发了计算不同植物根系分形维数的分形软件Fractal1.0。分析了两种植物倾斜、水平、垂直、相交、混合五种加根方式对土体强度的影响规律及两种植物根系对土体应力、应变的影响，揭示了根土相互物理作用的机理。并依据数值模拟中根系模型与实测根系形态的分形维数的关系，研究了植物根系分形维数与边坡土体位移场的关系，提出了基于分形维数的根系分布形态模型与土共同作用的植物方法边坡稳定性定量计算理论。主要创新成果如下：（1）描述了两种典型护坡植物狗牙根和夹竹桃根系的构型；从根长、根表面积、根体积、根干量、根长密度几个与根系固土护坡关系最为密切的形态学指标方面，确定了根系形态分布特征，并从根系构型和根系形态学方面分析了两种植物根系的固土能力。根据根系形态特征，研发了计算植物根系分形维数软件Fractal1.0，利用该软件能计算不同植物根系分形维数。（2）通过试验研究了狗牙根与夹竹桃两种植物根系的抗拉强度，得出植物根系的抗拉强度随植物根系直径的增大而减小的规律，并给出了根系直径与抗拉强度的相关拟合公式。（3）运用GDS三轴试验系统，首次研究了根系在土体中倾斜、水平、垂直、相交、混合五种不同布置方式对根土复合体强度的影响规律。获得了素土与加根土的应力—应变关系和抗剪强度参数值。试验结果表明根系不同布置方式对土体强度增强作用由大到小排序为混合放置＞相交放置＞竖直放置＞水平放置＞倾斜放置。（4）创新性地利用数值分析方法研究不同植物根系形态特征对边坡土体应力场与位移场的影响。依据数值模拟中根系模型与实测根系形态的分形维数的关系，研究植物根系分形维数与边坡土体位移场的关系，结果表明不同类别的植物对边坡土体的应力场和位移场影响是不同的，但都能有效减小边坡表层位移量，提高边坡稳定性。随着植入边坡土体的狗牙根根系须根长度、须根数量以及植株分布密度的增大，边坡表层位移量逐渐减小。随着植入边坡土体的夹竹桃根系侧根数量和植株分布密度的增大，表层位移量逐渐减小，其中主侧根夹角在45～60度的根系对于稳定土体效果最有效。（5）根据分形维数与边坡位移量拟合公式可知，分布密度为10株/米狗牙根植入边坡使边坡表层土体与未植入根系相比水平位移量减小41.2%，竖向位移量减小20.4%，总位移量减小20.9%。而分布密度为5株/米夹竹桃植入边坡使边坡表层与未植入根系相比水平位移量减小25.7%，竖向位移量减小7.7%，总位移量减小7.6%。（6）根据数值计算结果分析可知，两种植物根系对于边坡土体的稳定性仅限于边坡浅层土体，因此两种护坡植物根系固土的作用主要是增加浅层土体的粘聚力，限制浅层土体的侧向位移，在土体表层形成加筋网络作用，提高边坡土体表层的稳定性。（7）运用有限元法能够模拟土体与根系的共同作用，可形象直观地体现植物根系对于边坡表层应力场和位移场的影响，在实际护坡工程的实践中，可以运用有限元方法定量的分析植物护坡土体的应力应变情况，对于选择适宜的护坡植物和植被分布密度有一定的指导意义。（8）研究确定了根系分形维数与边坡表层位移量的关系，随着分形维数的增大，根系生长活性增大，根系分枝数量和分枝长度逐渐增大，植入边坡土体后，边坡表层位移量能够有效减小，因此植物根系分形维数大小能够反映根系对边坡土体稳定性影响。更多还原

【Abstract】 As an engineering technology, root reinforcement to slope has been widely applied in theslope protection, but the theoretical study on it has lagged behind practical applications. on thebasis of current literatures and the systematical study on the destroy principle of root-soilfriction bond, root morphological models, root-soil interaction and mechanical models, thisdissertation applies the fractal theory, Geotechnical engineering slope theory and Plant ecologytheory comprehensively and takes the interaction between soil and complex root group intoconsideration to provide theory basis and approaches to the application of quantitative rootresearch into the numerical analysis on slope stability. Meanwhile the dissertation offers atheory for the new artificial structures or reinforcement methods stimulating the root effects onslope reinforcement. The dissertation combines field investigation and lab experiments,experimental research and numerical stimulation to focus on the study of the distribution ofbermuda grass and nerium indicum root forms. On the basis of morphological characteristics ofthe roots, a fractal software Fractal1.0was developed to calculate fractal dimension for differentroots. The dissertation uncovers the root-soil interactions by analyzing the effects of tilted,horizontal, vertical, intersected and complex root-soil composites on the soil strength, as well asthe effects of the roots of both plants on the stress-strain of the soil. Besides, in the light of thefractal dimension between root models in numerical stimulation and actual measurements, therelevance between root fractal dimension and slope soil displacement field is studied and aquantitative calculation method on the slope stability reinforced by soil-root interaction is putforward in the dissertation.Main Innovations1. The root configurations of bermuda grass and nerium indicum are described; rootdistribution characteristics are determined from root length, surface area, volume, dry weightand length density, which are the most related morphological index to slope reinforcement; thereinforcement abilities of both plants are analyzed in terms of root configuration andmorphology; a fractal software Fractal1.0is developed specializing in the fractal dimension fordifferent roots.2. Tensile strengths of the roots of bermuda grass and nerium indicum are experimentedand a conclusion is drawn that the tensile strength of root decreases with the increase in rootdiameter; the related fitting formula on root diameter and tensile strength is also worked out.3. the effects of tilted, horizontal, vertical, intersected and complex root-soil compositeson the soil strength are studied for the first time with the help of triaxial test system; the stress-strain and shear strength parameter of both pure soil and rooted soil are obtained; theresults are concluded that the different root-soil composites can be sorted in descending orderby their soil-reinforcement abilities as following: complex root-soil composite, intersectedroot-soil composite, vertical root-soil composite, horizontal root-soil composite, tilted root-soilcomposite.4. The effects of stress field and displacement field of different roots characteristics onthe slope soil are studied by using numerical analysis in an innovative way. The relevancebetween root fractal dimension and slope displacement field is presented on the basis of therelevance between root models in numerical stimulation and actual measurements, which leadsto a conclusion that different plants has different effect on the stress field and displacement fieldon slope, but both can reduce displacement and enhance stability. As to the slope rooted withbermuda grass, the surface displacement is decreasing with the growth of the length, amountand distribution density of fibrous roots, while as to the slope with nerium indicum, the surfacedisplacement is decreasing with the growth of the amount and distribution density of lateralroots, most stable when the angle between tap and lateral root is45。～60。.5. As is shown through fractal dimension and the fitting formula on slope displacement,with bermuda grass rooted in at10plants per meter, the horizontal displacement of slopesurface soil reduces by41.2%, vertical displacement by20.4%and total displacement by20.9%respectively compared with the soil without plants in. With nerium indicum rooted in at5plantsper meter, the horizontal displacement of slope surface soil reduces by25.7%, verticaldisplacement by7.7%and total displacement by7.6%respectively compared with the soilwithout plants in.6. The reinforcements of both plants on the slope soil are restricted to the shallow layers.Therefore both roots serve to improve the cohesion and decrease lateral displacement ofshallow soil and play a role of reinforcement for soil surface.7. The root-soil interaction can be stimulated by finite element analysis to show theeffects of root on the surface stress field and displacement field of slope. Finite element methodcan be applied in practice to quantitatively analyze the stress-strain of slope soil and it alsoprovides guidance in selecting appropriate plant and distribution density.8. The relevance between and the slope surface displacement is determined. With thefractal dimension increasing, the root abundance and the amount of root branches are growingwhile the surface displacement reducing. Therefore the fractal dimension of roots can reflect theroot effects on the slope soil.更多还原