花岗岩残积土边坡草本植物根固效应试验

Experimental Research on Reinforcement Mechanism of Herbs Root System on Granite Residual Soil Slope

为了推进根系固土机制的定量研究,在前期边坡调查和植物筛选的基础上,人工种植了百喜草、假俭草、狗牙根3种常见的护坡植物,根据各深度下原状根-土复合体干密度、含水率和质量含根量等物理性质指标,设计了重塑根-土复合体直剪试验方案,实施了3种植物原状和重塑根-土复合体的直剪试验。结果表明:3种原状根-土复合体的抗剪强度在各级法向压力作用下均随含根量的增加而逐渐增大;3种原状根-土复合体的黏聚力和内摩擦角均随深度的增加而减小;3种植物根系在相同的土体状态下对黏聚力的影响排序为狗牙根>百喜草>假俭草;对土体内摩擦角的影响排序为假俭草>百喜草>狗牙根。植物根系增强土体抗剪强度的作用不仅受植物种类的影响,还与土体的干密度和含水率密切相关,干密度的增加对黏聚力的提升有显著影响,对内摩擦角的影响却并不大;3种植物重塑根-土复合体的最优含水率均为25%左右。在重塑根-土复合体的直剪试验中,很难探求含根量对抗剪强度指标的影响。

In order to promote the quantitative study on mechanism of root-soil reinforcement, three kinds of common herbs including Paspalum notatum, Eremochloa ophiuroides and Bermudagrass were selected and artificially planted based on slope investigation and plants selection, and the direct shear test for remolded root-soil composite of these three herbs were designed and implemented on the basis of physical properties of undisturbed root-soil composite, such as dry density, moisture content and root content of quality in different depths. The results showed that： the shear strengths of three undisturbed root-soil composites rose gradually with the increasing of the root content under different vertical pressure; the cohesions and internal friction angles of three undisturbed root-soil composites decreased with the increasing of depth. Under the same condition, the effects of three plant roots on the cohesion were sorted as follows： Bermudagrass〉 P. notaturn〉 E. ophiuroides,while the effects on the internal friction angle were sorted as follows： E. ophiuroides 〉 P. notatum 〉 Bermudagrass. The effects of plant roots on shear strength were not only affected by plant species, but also related to the dry density and water content of soil, and the increases of dry density had a significant influences on the cohesion, but had few effects on the internal friction angle. The most suitable moisture content for the three kinds of dis- turbed root-soil composite was about 25%. It was difficult to explore the influences of the root content on the shear strength index in the direct shear test of remolded root-soil composite.