【摘要】 为了评价黄土区草本植物根系固土抗蚀过程中对土体抗剪性能的增强效应,选取紫花苜蓿根系为研究对象,通过直剪试验研究不同土壤含水量、不同土层深度(10、20和30 cm)下的根-黄土复合体变化规律。结果显示:1)苜蓿根系能提高土体43. 10%～89. 41%的抗剪强度,增加13. 16～56. 95 mm的剪切位移; 2)苜蓿根-黄土复合体和裸地试样抗剪强度随土壤含水量的增加而减小,土壤含水量对土体抗剪强度产生负面效果; 3)苜蓿根系对土体抗剪性能的增强效应随土体剪切深度增加而减小,根系对浅表层土体抗剪强度的增强作用更为显著。研究结果对于植物固土护坡工程优势属种的筛选、边坡稳定性研究和黄土高原水土流失防治具有现实意义,可为边坡固土和水土保持植被措施提供理论依据。更多还原

【Abstract】 [Background] Surface erosion,slope instability and soil-water loss caused by soil erosion have become major ecological and environmental problems in China. Plant measures are commonly used ways in preventing soil erosion,and are also the most effective and fundamental methods for soil and water conservation. Shrub and grass have become priorities for solving the contradiction between water resources and ecological environment and preventing soil erosion. [Methods] Direct shear tests were conducted on loess soil samples with alfalfa roots,using the devices including direct shear box,frame,jack,hydraulic pump,displacement sensor,pressure sensor,recorder etc. The shear strength of alfalfa root-loess samples with various soil water contents and in different soil depth( 10,20,and 30 cm) were measured,the characteristics of shear failure of the soil samples and the distribution of the failure roots in shear plane were determined,and the relationship between shear strength and shear displacement of samples in different soil depth and with different soil water content were analyzed. [Results] 1) The alfalfa roots increased the shear strength of the soil by 43. 10%-89. 41%,and increased the shear displacement by around 13. 16-56. 95 mm. 2) The shear strength of both the alfalfa root-loess samples and rootless soil samples decreased with increasing soil water content, and the soil water content presented a negative effect on the shear strength of the soil. When the soil water content was 18. 97%,the shear strength of the soil composite sample was 10. 02 kPa and the shear displacement was 70. 55 mm.The maximum shear strength increased by 89. 41% and the shear displacement increased about 25 mm compared with the bare soil sample. 3) When the soil water content was about 30% in the shear depth of30 cm,the soil reinforcement effect of the root system was very limited. 4) The enhancement effect of alfalfa roots on soil shear strength decreased with the increase of soil shear depth,and the root system had a more significant effect on the shear strength of shallow soil. [Conclusions]The results are of practical importance to the selection of dominant species,to the improvement of slope stability and the prevention of soil and water loss on the Loess Plateau. It can also provide theoretical basis of vegetation measures for slope consolidation and soil and water conservation.更多还原