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 of 30 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.
赵家绪, 刘红星. 青海省突发性地质灾害分布规律及成因探析[J]. 青海国土经略, 2004(2):31. ZHAO Jiaxu, LIU Hongxing. Distribution law and cause analysis of abrupt geological hazards in Qinghai province[J]. Qinghai Land Strategy, 2004(2):31.
[2]
戚国庆, 胡利文. 植被护坡机制及应用研究[J]. 岩石力学与工程学报, 2006, 25(11):2220. QI Guoqing, HU Liwen. Vegetation slope protection mechanism and Application Research[J]. Journal of Rock Mechanics and Engineering, 2006, 25(11):2220.
王可钧, 李焯芬. 植物固坡的力学简析[J]. 岩石力学与工程学报, 1998, 17(6):687. WANG Kejun, LI Zhuofen. Mechanical analysis of plant slope stabilization[J]. Chinese Journal of Rock Mechanics and Engineering, 1998, 17(6):687.
[5]
OPERSTEIN V, FRYDMAN S. The influence of vegetation on soil strength[J]. Ground Improvement, 2000, 4(2):81.
[6]
NILAWEERA N S, NUTALAYA P. Role of tree roots in slope stabilization[J]. Bulletin of Engineering Geology and the Environment, 1999, 57:337.
[7]
李绍才, 孙海龙, 杨志荣, 等. 护坡植物根系与岩体相互作用的力学特性[J]. 岩石力学与工程学报, 2006, 25(10):2051. LI Shaocai, SUN Hailong, YANG Zhirong, et al. The mechanical properties of the interaction between the roots of slope protection plants and rock mass[J]. Journal of Rock Mechanics and Engineering, 2006, 25(10):2051.
[8]
李国荣, 毛小青, 倪三川, 等. 浅析灌木与草本植物护坡效应[J]. 草业科学, 2007, 24(6):86. LI Guorong, MAO Xiaoqing, NI Sanchuan, et al. Analysis of slope protection effects of shrubs and herbs[J]. Pratacultura Science, 2007, 24(6):86.
[9]
肖盛燮, 周辉, 凌天清. 边坡防护工程中植物根系的加固机制与能力分析[J]. 岩石力学与工程学报, 2006, 25(1):2670. XIAO Shengxie, ZHOU Hui, LING Tian Qing. Reinforcement mechanism and capacity analysis of plant roots in slope protection engineering[J]. Journal of Rock Mechanics and Engineering, 2006, 25(1):2670.
[10]
周云艳, 陈建平, 杨倩, 等.植物根系固土护坡效应的原位测定[J]. 北京林业大学学报, 2010, 32(6):1000. ZHOU Yunyan, CHEN Jianping, YANG Qian, et al. In situ measurement of the effect of plant roots on soil fixing and slope protection[J]. Journal of Beijing Forestry University, 2010, 32(6):1000.
[11]
朱锦奇, 王云琦, 王玉杰, 等. 基于试验与模型的根系增强抗剪强度分析[J]. 岩土力学报, 2014, 35(2):449. ZHU Jinqi, WANG Yunqi, WANG Yujie, et al. Analysis of root reinforcement shear strength based on test and model[J]. Geotechnical Report, 2014, 35(2):449.
[12]
卢海静, 胡夏嵩, 付江涛, 等.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[J]. 岩石力学与工程学报, 2016, 35(8):1712. LU Haijing, HU Xiasong, FU Jiang Tao, et al. In situ shear test of the shear strength of soil soil slope reinforced by cold and dry environment plants[J]. Journal of Rock mechanics and Engineering, 2016, 35(8):1712.
[13]
胡夏嵩, 李国荣, 朱海丽, 等. 寒旱环境灌木植物根-土相互作用及其护坡力学效应[J]. 岩石力学与工程学报, 2009, 28(3):613. HU Xiasong, LI Guorong, ZHU Haili, et al. The root soil interaction of shrubs and plants in cold and drought environment and the mechanical effects of slope protection[J]. Journal of Rock Mechanics and Engineering, 2009, 28(3):613.
[14]
孟军江, 唐成斌, 钱晓刚, 等.喀斯特山区退耕坡地紫花苜蓿引种栽培试验[J].贵州农业科学, 2005, 33(6):51. MENG Junjiang, TANG Chengbin, QIAN Xiaogang, et al. Introduction and cultivation experiment of alfalfa on sloping land of converted farmland in karst mountainous area[J]. Guizhou Agricultural Science, 2005, 33(6):51.
[15]
马树升, 王振诚, 王金宝.山丘区坡地种植紫花茵稳蓄水保土效果研究[J].山东水利专科学校学报, 1998, 10(2):65. MA Shusheng, WANG Zhencheng, WANG Jinbao. Study on the effect of planting Zihua Yin on slope land in hilly area[J]. Journal of Shandong Water Conservancy College, 1998, 10(2):65.
[16]
杨吉华, 张光灿, 刘霞. 紫花苜蓿保持水土效益的研究[J].土壤侵蚀与水土保持学报, 1997, 3(2):91. YANG Jihua, ZHANG Guangcan, LIU Xia. Study on Soil and water conservation benefits of alfalfa[J]. Journal of Soil Erosion and Soil and Water Conservation, 1997, 3(2):91.
[17]
WU T H, MCKINELL W P, SWANSTON D N. Strength of tree roots and landslides on Prince of Wales Island, Alaska[J]. Can Geotech J, 1979, 16(1):19.
[18]
周跃, 陈晓平, 李玉辉, 等. 云南松侧根对浅层土体的水平牵引效应的初步研究[J]. 植物生态学报, 1999, 23(5):458. ZHOU Yue, CHEN Xiaoping, LI Yuhui, et al. Preliminary study on horizontal traction effect of lateral roots of Yunnan pine on shallow soil[J]. Chinese Journal of Plant Ecology, 1999, 23(5):458.
[19]
格日乐, 左志严, 蒙仲举. 杨柴根系提高土体抗剪特性的研究[J]. 水土保持学报, 2014, 28(4):72. GE Rile, ZUO Zhiyan, MENG Zhongju. Study on improving shear properties of soil by Yangchai root[J]. Journal of Soil and Water Conservation, 2014, 28(4):72.
[20]
侍倩.植被对斜坡土体土力学参数影响的试验研究[J]. 岩土力学, 2005, 26(12):2027. SHI Qian. Experimental study on the effect of vegetation on soil mechanical parameters of slopes[J]. Geotechnical Mechanics, 2005, 26(12):2027.
2019, Vol. 17 
