基于多尺度耦合模型的林木根系固土机制研究

Loess Plateau is one of the most serious region with soil and water loss in China. Gravity erosion including landslide disaster is quite serious. The effect of vegetation roots on soil reinforcement and landslide prevention cannot be ignored. Previous research on the root reinforcement focused on the influence of the single root or root bundle on the soil. However, research for accurately predicting the effects of complex root groups on slope reinforcement remains insufficient. The roots of artificial shelter forest are investigated in this project. Based on root morphology, the multiscale coupling mechanical model of roots and soil is proposed using homogenization theory and fractal theory. Moreover, this model is validated by root morphology analysis, three-axial compression tests and in-situ direct shear tests. Finally, the influence of the factors including tree age, species, spatial layout and soil properties on the slope stability is investigated. This project tries to apply the homogenization theory in the field of material science to study the mechanical properties of the root-soil composites. The research perspective is extended from the single root to root groups. This project aims to establish the coupling relationships between the three different scales including the microscopic root system, mesoscopic “roots of plant individual and surrounding soil”, and macroscopic vegetated slope. The mechanism of root-group reinforcement is explained by the principle of periodic composite materials. The research does shed light on accurately evaluating the stability of vegetated slopes. The methods can also be applied to shrubs, herbs and mixed vegetation communities.

黄土高原是我国水土流失最严重的地区之一，滑坡等重力侵蚀相当严重，植被根系固持土壤、抑制滑坡的作用不可忽视。关于根系固土的研究多关注于单根或根束对土体的影响，然而准确预测复杂根群对边坡加固效果的研究还存在不足。本项目以人工护坡林为研究对象，主要研究：（1）利用均匀化理论和分形理论，构建基于根系形态的“根系-土体”多尺度耦合力学模型；（2）通过根系形态分析、三轴压缩试验和原位直剪试验，验证多尺度模型；（3）应用该模型，揭示林龄、树种、空间配置和土壤特性等因素对边坡稳定性的影响规律。本项目尝试将材料学中的均匀化理论运用于根土复合体力学性质的研究，将研究视角从单根拓展到根群，旨在建立微观根系、细观“植株根系-根周土”与宏观含林边坡三种尺度之间的耦合关系，从周期复合材料的角度解释根群固土机制，为准确评价含林边坡的稳定性提供新的思路和技术手段，研究成果同样可以推广适用于灌木和草本根群及混合根群。

黄土高原是我国水土流失最严重的地区之一，滑坡等重力侵蚀相当严重，植被根系固持土壤、抑制滑坡的作用不可忽视。关于根系固土的研究多关注于单根或根束对土体的影响，然而准确预测复杂根群对边坡加固效果的研究还存在不足。本项目以人工护坡林为研究对象，主要研究：（1）利用均匀化理论和分形理论，构建基于根系形态的“根系-土体”多尺度耦合力学模型；（2）通过根系形态分析和三轴压缩试验，验证多尺度模型；（3）揭示降雨、树种、空间配置和土壤特性等因素对边坡稳定性的影响规律。本项目将材料学中的均匀化理论运用于根土复合体力学性质的研究，将研究视角从单根拓展到根群。研究结果表明：渐进均匀化理论不仅能准确地构建根土复合体本构关系，而且极大地减少了模型计算工作量（减少了95.58%的单元数）；当边坡坡度较小时（坡角为30°），无（草）根边坡安全系数较大（F=4.28），根系对边坡的稳定性加持较小（平均仅提高2.92%）；当坡角增大到45°时，含（草）根边坡平均安全系数提升了13.45%，根系固土效果更加显著。本项目为准确评价含林/草边坡的稳定性提供新的思路和技术手段，研究方法推广用于具有周期性构造的城市森林减振降噪研究。