【作者】 王萍花；

【导师】 陈丽华；

【作者基本信息】 北京林业大学 ， 水土保持与荒漠化防治， 2012， 硕士

【摘要】 为探索乔木阻止浅层滑坡、固持水土的力学机制,本文采用室内轴向拉伸试验对华北土石山区4种常见乔木：油松、白桦、落叶松和蒙古栎进行单根拉伸试验,测定其单根的抗拉力学特性；定性分析了直径、树种、标距以及拉伸速率等因素对抗拉强度、最大抗拉力和应力-应变关系的影响；在此基础上,进一步定量分析建立了单根抗拉强度的综合模型和描述应力-应变关系的经验模型。然后,选取油松根系作为试验根样与华北木兰围场取回的土样一起制备成根土复合体试样,采用全自动三轴压缩仪对复合体进行剪切试验,对复合体的剪切特性进行研究分析。主要研究成果如下：(1)4种乔木根系抗拉强度的水平：白桦>蒙古栎>油松>落叶松；4个研究树种根系的抗拉强度均与直径呈负相关关系；在同一径级下,标距与抗拉强度呈负相关关系；拉伸速率对其根系抗拉强度水平的影响均不太明显。(2)乔木单根的应力应变曲线整体都为单峰曲线,没有出现明显的径缩现象。四种乔木的应力应变曲线都表现出弹塑性材料特征,只是在受拉的初期阶段,表现为弹性材料特征；应力超过弹性极限,根系变形迅速进入弹塑性变形阶段。(3)引入了树种、标距作为控制变量,对4个树种根系构建林木单根抗拉的力学特性综合模型,其数学表达式为P=a(S,L)+b(S,L)/D。此模型在一定程度上能反映林木单根的力学作用机制,有一定的实际指导意义。(4)建立了一个反映林木单根本构关系的经验模型,并从数学角度,对模型进行了理论论证,推导给出了模型相关参数的计算方法。(5)加根能够明显提高土体抵抗剪切破坏的能力,且垂直加根的效果强于水平加根的效果,围压的增加和埋入根段直径的增大都使这种加强效果更为明显。更多还原

【Abstract】 To explore the tree to prevent shallow slope, retaining water and soil mechanism, indoor axial tensile test of a single tensile tests were taken on the four kinds of common trees of the North China in mountainous area:Pinus tabulaeformis, birch, larch and Mongolian oak, and itssingle tensile mechanical properties were determinated; qualitative analysis of the diameter, species, distance and stretching rate and other factors were taken on the tensile strength, resistance to tension and stress-strain relations; on this basis, further quantitative analysis were taken to establish a single tensile strength of the model and describe the stress-strain relationship of empirical models. Then, Pinus tabulaeformis roots were selected as test root samples with the North China Hunting retrieve soil samples with the preparation of the root soil composite sample, using fully automated triaxial compression shear test in complex to study the complex shear characteristics.The major results were summarized as follow:(1) Level of tensile strength of four kinds of tree roots:birch> Mongolian oak> Pinus tabulaeformis> larch; four species root tensile strength was negatively correlated with the diameter gauge; in the same diameter class, root length and tensile strength was negatively correlated; the influence of stretching rate on root tensile strength is less obvious.(2) The stress-strain curve of single arbor root was a single peak curve, there was no obvious diameter reduction. Four trees in the stress-strain curves show the elastic-plastic material characteristics, but in the early stages of tensile, showed elastic material characteristics; once stress exceeds the elastic limit, root deformation rapidly went into the elastic and plastic deformation stage.(3) Introduced species, troot length as a control variable to build a comprehensive model of forest single tensile mechanical properties of four species roots, its mathematical expression for P=a(S,L)+b(S,L)/D. To some extent this model can reflect the trees of a single mechanical mechanism, a certain degree of practical significance.(4) An empirical model was established to reflect the single roots constitutive relation, and from a mathematical perspective, the theory argumentation and derivation of model were taken and its parameters were calculated out.(5) Root-soil can significantly improve the ability of soil to resist shear failure, and the effect of perpendicular to add the root is stronger than that of in the level of the root effect; the increase of confining pressure, and buried in the root segment diameter increases this strengthening effect is more obvious.更多还原