三峡库区紫色土的植物根系加固效应与机制研究

It is the one of the most important measures to restore ecological environment and enhance the shallow soil layer stability of slope that using vegetation to protect and reinforce the soil in Three Gorges Reservoir Area (short as TGRA). The project, based on field investigation, in-situ test and laboratory experiment, taking purple soil, plant roots and purple soil-roots system as the research objects, is to study the root reinforcement effect and mechanism to the purple soil in TGRA combining physical and mechanical characteristics of purple soil, distribution structure and mechanical properties of plant roots. The mainly studies of plant root's distribution structure are spatial distribution and the change with plant growing of underground biomass, root cross-section and geometric features. The key research of mechanical properties of plant roots are tensile property and friction relationship between roots and purple soil. From the perspective of physical and mechanical stability of purple soil-root system under different root's distribution structure, it is to measure slaking and shear strength and then analyze the root reinforcement effect and action range to purple soil. Making the mathematics representation of the roots characteristics and through the correlation analysis between mathematics representation and root reinforcement effect, it is to reveal the root reinforcement mechanism to purple soil. The research of this project would be benefit to stability maintenance of purple soil and hope to perfectly provide certain scientific reference for species selection, plant community construction and regulation of ecological restoration engineering in TGRA.

利用植被对三峡库区土壤进行防护，是恢复库区边坡生态环境、提高浅层土体稳定性的重要措施。项目通过野外调查、原位试验和室内控制试验，以三峡库区紫色土、植物根系及二者形成的紫色土-根系系统为研究对象，结合紫色土的物理力学特性、根系的分布结构及力学特性，研究植物根系对三峡库区紫色土的加固效应和机制。其中，根系的分布结构着重研究根系的地下生物量、根截面积、几何特征等在空间上的分布及随株龄的变化；根系的力学特性着重研究根系抗拉性能和根土之间的摩擦关系；从不同根系分布结构下的紫色土-根系系统的物理稳定性和力学稳定性角度，分别测定其水崩解性、抗剪性能，分析根系对紫色土的加固效应及作用范围；对根系分布结构进行数学表达，并与根系固土效应进行相关分析，揭示植物根系对紫色土的加固机制。项目开展有利于三峡库区紫色土稳定性维持和紫色土资源的利用，可为紫色土生态修复工程的物种选择、群落构建与调控提供一定的科学依据。

利用植被对三峡库区土壤进行防护，是恢复库区边坡生态环境、提高浅层土体稳定性的重要措施。.本项目通过开展草灌植物根系抗拉力学特性、根系抗拉拔力的影响因素、多花木蓝根系加筋效应及抗拔模型、根系固土模型中根系表观粘聚力的分析与改进、根系-土-岩接触面剪切特性、草灌植物根系对坡体表面土壤的渗透作用影响、抗蚀性抗冲性增强效应试验、植被对坡面产流产沙影响的试验等，针对植物根系对三峡库区紫色土的加固效应和机制以及植被对紫色土坡面的水土保持效应进行了试验研究和理论分析。.研究表明：根系的直径、含水量、空间分布等不同程度地对单根抗拉强度产生影响；根径一定时多花木蓝单根的最大抗拉拔力随着土壤容重的增加而呈现增大的趋势；含根系试样的抗剪强度均大于无根系试样且存在使根-土复合体的抗剪强度出现最大值的最优含根量区间；所提出的根系表观粘聚力计算改进方法能使理论计算值与实测值吻合度较好；根系作用对土-岩界面进入残余阶段具有明显的延滞作用；草灌植物能改善土壤的渗透性能，显著增强土壤抗冲、抗蚀性；有植被的坡面较裸坡具有显著的减流减沙效应。.研究成果可为三峡库区土地资源的保护和合理开发、裸地的生态恢复提供一定的理论指导。