中文摘要：

在自行设计、加工的原位剪切试验装置中分别种植灌木植物霸王和柠条锦鸡儿,通过对2种坡度的素土、霸王根–土复合体和柠条锦鸡儿根–土复合体进行原位剪切试验,测得素土和根–土复合体抗剪力、抗剪强度的动态变化,评价灌木植物护坡的时间效应,并采用室内直剪试验方法检验原位剪切试验结果的合理性。试验得出以下结论：（1）根–土复合体的抗剪力和抗剪强度均大于同种坡度的素土,即植物根系可显著提高边坡土体的抗剪能力,且霸王根–土复合体抗剪力和抗剪强度主要体现在剪切面处断裂根系的抗拉或抗剪作用、拔出根系的根–土摩擦力及滑移根系的锚固、摩擦作用,柠条锦鸡儿根–土复合体主要体现在根系的锚固和根–土摩擦作用,同时,素土和灌木根–土复合体的抗剪力和抗剪强度随着坡度的增加而减小;（2）素土的剪切力在3 s左右达到峰值,而根–土复合体的剪切力峰值时间为69.8～168.2 s;素土试样在剪切位移为1 mm内抗剪强度均达到峰值,而剪切位移为23.13～83.13 mm时霸王根–土复合体和柠条锦鸡儿根–土复合体抗剪强度达到峰值,即根–土复合体的剪切力峰值时间、抗剪强度峰值位移均较素土相对滞后,这反映了在剪切过程中根系的抗拉能力、根–土界面的摩擦作用逐步转化为根–土复合体的抗剪能力,从而延缓坡面变形破坏的时间;（3）为了验证原位剪切试验结果的准确性,对素土和灌木根–土复合体进行室内直剪试验,其抗剪强度值与原位剪切试验值接近,反映原位剪切试验及其结果的合理性。上述研究成果对于开展研究区西宁盆地及其周边地区坡面水土流失、浅层滑坡等地质灾害的防治,以及对青藏高原东北部黄土地区边坡生态工程建设、区域生态环境保护具有重要的理论指导价值和现实意义。

英文摘要：

Zygophyllum xanthoxylon and Caragana korshinskii are shrubs planted separately in in-situ shear test devices designed and worked out by the researchers.The dynamic variation on the shear resistance,shear strength of the soil without roots and root-soil composite systems are observed from two degrees of slope via in-situ shear test on soil without roots,Zygophyllum xanthoxylon root-soil composite system and Caragana korshinskii root-soil composite system.At the same time,the time effect of slope protection for shrubs is evaluated;and the accuracy of the in-situ shear test is proved by indoor direct shear tests.The results show：（1） At the same degree of slope,the shear resistance and shear strength of root-soil composite system are larger than those of soil without roots,i.e.plant roots can significantly improve the shear capability of slope soil.The shear resistance and shear strength of Zygophyllum xanthoxylon root-soil composite system are reflected in tension or shear of broken roots,friction between soil and pulled-out roots,anchor and friction of slipped roots,while those of Caragana korshinskii root-soil composite system from the anchor of roots and friction between roots and soil.The shear resistance and shear strength of soil without roots and shrub root-soil composite systems decrease with the slope degree increase.（2） The shear resistance of soil without roots reaches its peak value after three seconds,while that of root-soil composite system reaches the peak values after 69.8 to 168.2 seconds.The shear strength of soil without roots reaches the peak value when the displacements are within one millimeter,while that of root-soil composite system reach the peak values when the displacements are from 23.13 to 83.13 millimeter,i.e.the peak time of shear resistance and peak displacement of shear strength for root-soil composite system appear later than those of soil without roots.Those findings reflect that the tensile capability of roots and the friction between roots and soil during the process of