植物根系构型与力学特性对黄土区浅层坡体稳定性的影响

There are countless natural slopes and many engineering slopes in Loess Region. Whereas, the overall risk of landslide or mass movement on these slopes is potentially high and the biological protection of them is very necessary..In the aspect of biological plant protection, the main influencing factors are root architecture and mechanics traits. Whereby, this research plans to select some plants that are used normally in local slope protection application, aims to 1) illustrate their plastic and elastic mechanics focused on tensile strength with different diameter using machine of tensile strength testing, 2) to demonstrate the indices of root architecture and its three dimensional distributions, 3) upon the measured indices of root architecture and mechanics traits, the contributions of them to shear resistance reinforcement of root-soil compound pillar will be analyzed and simulated by Wu-Waldron model, 4) in the end, several case research of slope stability would be conducted to demonstrate the factor of safety reinforced by different plants. .We plan to use the three dimensional sampling method, which can expose roots progressively downward and outward from plant stem and sample soil pillars with their coordinate positions. The pillars will be tested using direct shear machine. The root samples obtained from the three dimensional sampling method will be scanned and the pictures will be analyzed to elicit indices of root architecture and morphology. Besides that, for the sake of obtaining a fine three dimensional root architecture, a three dimensional digitized model for each selected plant will be constructed by a 3D scanner and digitizer when the roots are exposed using digging and air compressor-soil removing methods. .The results are expected to provide theoretical bases for selecting slope-protection plant species and for slope stability evaluation and their inputs of slope stability software.

黄土区沟壑纵横，存在较多的自然坡体与工程坡体，这些坡体存在潜在的滑塌风险，因而坡体的生物防护非常必要。研究拟以植物影响坡体防护效果的主要因素-根系构型和力学特性出发，选取黄土区主要适生护坡植物，通过根系拉力仪、三维土柱坐标法+2D透扫仪、原位风机吹挖根+3D扫描数字化仪和剪切仪等，研究不同直径、不同根系类型黄土区典型植物单根弹塑性力学特性；根际范围内径向和垂向三维根系构型主要参数及其分布；根系力学特性、根系构型各参数与根-土复合体抗剪性关系，及其对抗剪增强贡献；在以上研究基础上，通过Wu-Waldron模型模拟不同护坡根系范围内抗剪增强三维分布；最后使用Slip4EX软件进行黄土区坡体稳定性案例研究。研究有望为坡体稳定性评价软件参数设计与输入，及黄土区护坡植物选择与水土保持工程设计提供理论依据。

黄土区水土流失比较严重，生态护坡是比较推崇的防护手段，而植物在生态固土护坡中起到很重要的作用。本文以黄土区常见的优势乡土灌木达乌里胡枝子、沙棘和狼牙刺为研究对象，野外采用三维土柱挖取灌木的根系，进行不同直径单根抗拉试验、原状土根土复合体的剪切试验和使用三维土柱坐标法+运动追踪仪，对常见植物根系进行了三维实体建模与形态、构型和拓扑参数提取与分析。之后，使用三维土柱坐标法+运动追踪仪，对常见植物根系进行了三维实体建模与形态、构型和拓扑参数提取与分析，并根据抗剪增强库仑公式模拟了根际范围内不同植物通过抗剪增强作用的固土护坡效果。.（1）达乌里胡枝子、沙棘和狼牙刺三种灌木的根系主要分布于0-40 cm土层中，根系生物量分别约占总量的91.34%、89.92%和73.89%。（2）达乌里胡枝子、沙棘和狼牙刺的抗拉力（Tensile Resistance, TR）与抗拉强度（Tensile Strength, TS）都表现为直径（D）的幂函数(aDb),其中抗拉力与直径呈正相关（b>1），；而抗拉强度与直径呈负相关（b<1）。（3）三种灌木根际范围几随土层加深，达乌里胡枝子根土复合体的抗剪强度，表现出先增加减少而后增加又减少的趋势，沙棘和狼牙刺根土复合的抗剪强度表现出先增加后减少的趋势。其中猪毛蒿、狗尾草、白羊草、达乌里胡枝子、拓扑指数都基本接近于1，拓扑指数只有沙棘和狼牙刺稍小，但也都倾向于鱼尾型分根，该种分根类型对有限养分的吸收较好，适应于养分贫瘠地区，但根系的拓殖能力不够。猪毛蒿、狗尾草、白羊草、达乌里胡枝子、中国沙棘和狼牙刺都具有比较低的分形维数，介于1.003-1.378，而分形丰度较高，介于2.277-3.742，说明分根结构都相对简单，根系在空间占有上较为集中。相对的，沙棘、白羊草和狼牙刺具有相对较高的分形维数且具有较大的根际分布范围，具有相对较好的固土护坡作用。