植物根系固土护坡机理的研究进展及展望

在综合国内外相关研究成果的基础上,详细介绍了近几年来植物根系固土护坡机理的研究进展。文章分别从水文效应和力学效应2个方面对根系固土护坡机理进行了介绍,并着重从根增强的理论模型、根-土相互作用等方面论述了植物根系固土护坡的力学效应。首先介绍了根增强理论的先驱模型Wu和Waldron模型,文章从多方面论证了Wu和Waldron模型假定穿过剪切面的所有根在受力时同时破坏高估了根的增强作用,详细介绍了国外学者对Wu和Waldron模型改进后,最新提出的2种考虑根系逐渐破坏的力学模型——纤维束增强模型FBM和根束增强模型RBM。FBM模型用动态纤维束来模拟根系的渐进破坏,假设荷载被分配给束中的每个根,当载荷增加到其值超过了某单根的抗拉强度时,该根被拉断,而被该根分担的载荷被重新分配到剩下的完好的根中,直到所有的根都拉断。该模型使用应力控制的加载过程,不能得到完整的力-位移关系曲线;且该模型中没有考虑根的直径分布、几何性质、力学性质等的影响。为了克服上述缺陷Schwarz在FBM模型的基础上,又提出了RBM模型。RBM模型是一个以位移控制加载过程的纤维束模型,该模型考虑整个根束的拔出力是位移的函数,并被表示成单根的拔出力之和。文章最后详细论述了根系的拔出机理,探讨了植物根系固土护坡研究的发展方向。

Progress of study on soil reinforcement mechanisms by root and its expectation

Based on relevant research results both at home and abroad, the paper described in detail the progress of study on the mechanism in recent years in plant roots reinforcement soil. Soil reinforcement mechanisms by plant root were introduced respectively, from two aspects of the hydrological effects and mechanical effects, and the mechanical effects were especially described from the root enhancement theoretical model, the root-soil interaction and other aspects. First introduced the root enhanced theory pioneer model of Wu and Waldron model, the paper in many ways demonstrates the Wu and Waldron model overestimating the enhanced role of the root which assumes all roots through the shear plane under an increasing load break simultaneously, and described in detail the two latest considering roots progressive failure mechanical models which proposed by foreign scholars on the basis of the Wu and Waldron model--the Fiber Bundle Model（FBM） and Root Bundle Model（RBM）. The FBM model simulated roots in soils as a bundle of fibers that rupture progressively under an increasing load, assumed load assigned to each root in the bundle, when the load increased its value more than the tensile strength of a single root which pulled off, and the sharing load of the root was re-assigned to the remaining intact roots until all the roots pulled off. However, FBM model did not take into account the combined effects of root diameter distribution, geometry and mechanics, and because in the model bundle deformation controlled by load instead of displacement, the root bundle force-displacement curve not available past the maximum force. To remedy some of these issues Schwarz proposed the Root Bundle Model on the basis of FBM model. RBM was a displacement-controlled fiber bundle model, to estimate the pullout force of root bundles as a function of displacement and the sum of the single pullout force. Finally, discussed in detail the root pull-out mechanism, and explored the direction of development of study on soil reinforcement mechanisms by root.