寒旱环境植物根系增强边坡土体抗剪强度的原位剪切试验研究

In-situ shearing test on the shear strengh of soil slope reinforced by plant roots in cold and arid environments

选取西宁盆地及其周边地区作为试验区,以种植在试验区30°边坡生长期为150 d的垂穗披碱草、细茎冰草等2种草本和柠条锦鸡儿、霸王等2种灌木为供试种,采用草本和灌木单一种植以及组合种植等2种方式,分别开展原位剪切试验评价植物根系增强边坡土体抗剪强度贡献;在此基础上,将本次试验结果与Wu-Waldron-Model模型（简称WWM模型）计算结果进行对比分析,得出如下结论：（1）根–土复合体抗剪强度较素土表现出较大程度提高,采用单一种植草本和灌木的根–土复合体抗剪强度增幅为47.61%~98.24%;草本和灌木混合种植的根–土复合体抗剪强度增幅则为104.47%~173.93%,同时反映出草本和灌木混合种植条件下的根–土复合体抗剪强度增幅,显著大于单一种植条件下的根–土复合体抗剪强度增幅。（2）通过将WWM模型计算结果与原位剪切结果进行对比,对比结果表明：采用WWM模型计算得到的单一种植和组合种植2种条件下,根–土复合体抗剪强度增量变化规律与原位剪切试验得到的抗剪强度增量变化规律基本一致,上述结果实现了采用原位试验和模型理论计算相结合的方法,定量评价试验区草本和灌木根系增强边坡土体抗剪强度贡献。

Xining basin and the surrounding area were selected as the experimental zone. 2 herbs-Elymus dahuricus and Agropyron trachycaulum and 2 shrubs-Caragana korshinskii and Zygophyllum xanthoxylon,had been growing on the slope with the angle of 30° for 150 days. In-situ shear tests were conducted to estimate the contribution of plant roots in enhancing shear strength of soil in two scenarios,the herbs only or shrubs only planting and the mixture of herbs and shrubs planting. On this basis,Wu-Waldron-Model（WWM） was used to evaluate the effects of both the single planting and mixed planting of herbs and shrubs in reinforcing the slope soil. The values calculated with WWM and from in-situ shear tests were compared. The results of in-situ shear tests on the root-soil composite systems showed that the shear strength of the samples of root-soil composite system improved more significantly than the samples of soil without roots. The shear strength of the root-soil composite systems with monoculture herb or shrub increased from 47.61% to 98.24%,and the shear strength of root-soil composite systems with mixed herbs and shrubs increased from 104.47% to 173.93%,indicating that the effect of reinforcement of the mixed planting of herbs and shrubs are better than that of monoculture. Under two kinds of planting forms（single planting and mixed planting）,the shear strength of root-soil composite systems from WWM model and in-situ shear test are basically consistent.