(1. Department of Geological Engineering，Qinghai University，Xining，Qinghai 810016，China；2. Qinghai Institute of Salt Lakes，Chinese Academy of Sciences，Xining，Qinghai 810008，China)
Abstract：The triaxial compression tests have been conducted in cold and arid environments on four samples：soil without roots，herb root-soil composite system，shrub root-soil composite system and shrub root-herb root-soil composite system. By comparing the strength and corresponding stress-strain properties of the four samples，the effects of the roots reinforcement on soil and slope protection have evaluated. The results show that：(1) Under the confining pressure at 20，30 and 40 kPa，the main stress differences of root-soil composite system and soil without roots increase with the growing of axial strain，finally drive to the stable values. The relationship curves of main stress difference and axial strain belong to the strain hardening type. The shear capability of root-soil composite systems increases more quickly than that of soil without roots at the early stage of loading. (2) Under three degrees of confining pressure，the shear strength peaks of root-soil composite system samples are larger than that of soil without root，and the order of the shear strength peaks of the four samples from big to small is caragana korshinskii root-achnatherum splendens root-soil composite system＞achnatherum splendens root-soil composite system＞caragana korshinskii root-soil composite system＞soil without root. (3) Compared with soil without roots, the increasing ratio of cohesion of three root-soil composite system are 94.1%，66.6%，39.2% respectively. The increasing ratio of the combination of Caragana korshinskii root and Achnatherum splendens root-soil composite system is 16.5% bigger than Achnatherum splendens root-soil composite system，39.4% bigger than Caragana korshinskii root-soil composite system. The varying law shows that plant roots have obvious effects on slope reinforcement，especially the combination of herb roots and shrub roots，which owns greater effects than herb roots or shrub roots alone. The achievements can supply theoretical reference for geological catastrophes，such as soil and water loss，shallow landslide in the testing area and other areas with similar natural environments.
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2012, Vol. 31 
