不同根系分布模式下的土坡抗剪性能研究
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摘要
以香根草根系及其所在土壤构成的根-土复合体为研究对象,通过室内直剪试验,探讨不同含水率和垂直压力条件下,不同根系分布方式对复合体抗剪性能的影响。结果表明:根系数量和径级相同时,在土壤天然含水率和2～3 m土层压力下,当所有根系均垂直于剪切面时,根系分布越集中,对根-土复合体抗剪强度的提升越明显;当根系以不同的空间角度均匀分布时,根-土复合体抗剪强度相对于素土的增长率大小顺序为根系全部垂直的分布方式(M_a)<根系全部呈45°倾斜的分布方式(M_b)<根系一半倾斜45°一半垂直的分布方式(M_c)。在天然含水率条件下,随着垂直压力的增大,根-土复合体的抗剪强度增长率呈现先减小后增大的趋势;随着含水率增大,土体内摩擦角先增大后减小,黏聚力总体呈减小趋势。
This study aimed to identify the root distribution traits conferring the most resistance to soil during shearing by direct shear tests. It adopted soil reinforcement by roots of 1-year-old vetiver(Vetiveria zizanioides(L) Nash). The outcomes show that with the same root number and diameter, the natural soil moisture content and the soil pressure in the soil depth of 2-3 m and when all the roots are perpendicular to the shear surface, the more concentrated root distribution mode led to the more significant improvement in the shear strength of root-reinforced soils. Among 3 root distribution modes, the increasing rates of the shear strength in root-reinforced soils are increased according to the following order: the first mode(M_a) in which root systems is perpendicular to the shear surface; the second mode(M_b) in which root systems formes the angle of 45° with the shear surface; the third mode(M_c) in which 50% root systems is perpendicular to the shear surface and 50% root systems form the angle of 45° with the shear surface. Under the conditions of natural water content and with the increase in the vertical pressure, the increasing rate of the shear strength of root-soil complexes firstly decreases and then increase. With the increase of water content, the angle of internal friction in soil firstly increases and then decreases, whereas the cohesion decreases.
This study aimed to identify the root distribution traits conferring the most resistance to soil during shearing by direct shear tests. It adopted soil reinforcement by roots of 1-year-old vetiver(Vetiveria zizanioides(L) Nash). The outcomes show that with the same root number and diameter, the natural soil moisture content and the soil pressure in the soil depth of 2-3 m and when all the roots are perpendicular to the shear surface, the more concentrated root distribution mode led to the more significant improvement in the shear strength of root-reinforced soils. Among 3 root distribution modes, the increasing rates of the shear strength in root-reinforced soils are increased according to the following order: the first mode(M_a) in which root systems is perpendicular to the shear surface; the second mode(M_b) in which root systems formes the angle of 45° with the shear surface; the third mode(M_c) in which 50% root systems is perpendicular to the shear surface and 50% root systems form the angle of 45° with the shear surface. Under the conditions of natural water content and with the increase in the vertical pressure, the increasing rate of the shear strength of root-soil complexes firstly decreases and then increase. With the increase of water content, the angle of internal friction in soil firstly increases and then decreases, whereas the cohesion decreases.
引文
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[14] MICKOVSKI S B, SONNENBERG R, BRANSBY M F, et al. Shear Reinforcement of Soil by Vegetation[J]. Millpress Science Publishers, 2007,3(4):24-27.
[15] MICKOVSKI S B, BENGOUGH A G, BRANSBY M F, et al. Material Stiffness Branching Pattern and Soil Matric Potential Affect the Pullout Resistance of Model Root Systems[J]. European Journal of Soil Science,2007,58(6):1471-1481.
[16] ENDO T, TSURUTA T. The Effect of Tree Roots upon the Shearing Strength of Soil[G]//Annual Report of the Hokkaido Branch. Tokyo: Government Forest Experimental Station, 1969:167-179.
[17] THOMAS R E, POLLEN-BANKHEAD N. Modeling Root-Reinforcement with a Fiber-Bundle Model and Monte Carlo Simulation[J]. Ecological Engineering, 2010, 36(1): 47-61.
[18] DOCKER B B, HUBBLE T C T. Quantifying Root-Reinforcement of River Bank Soils by Four Australian Tree Species[J]. Geomorphology,2018,100(3-4):401-418.
[19] MAO Z, SAINT-ANDRE L, GENET M, et al. Engineering Ecological Protection Against Landslides in Mountain Forests: Choosing Cohesion Models[J]. Ecological Engineering,2012,45: 55-69.
[20] 肖宏彬,赵亮,李珍玉,等.香根草根系的分布形态及抗拉强度试验研究[J].中南林业科技大学学报,2014,34(3):6-10.
[21] 宋维峰,陈丽华,刘秀萍. 林木根系固土作用数值分析[J]. 北京林业大学学报,2006,28(增刊2):80-84.
[22] 倪九派,袁天泽,高明,等.土壤干密度和含水率对2种紫色土抗剪强度的影响[J]. 水土保持学报,2012,26(3):72-77.
[23] NORMANIZA O,FAISAL H A,BARAKBAH S S. Engineering Properties of Leucaena leucocephala for Prevention of Slope Failure [J].Ecological Engineering, 2008,32(3):215-221.
[24] 格日乐,张成福,蒙仲举,等. 3种植物根-土复合体抗剪特性对比分析[J]. 水土保持学报,2014,28(2):85-90.
[25] 格日乐,左志严,蒙仲举,等. 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):72-77.
[2] NORRIS J E, GREENWOOD J R. Slope Stability and Erosion Control: Ecotechnological Solutions[M]. Springer Netherlands,2008:9-15.
[3] OSMAN N, BARAKBAH S S. Parameters to Predict Slope Stability-Soil Water and Root Profiles[J]. Ecological Engineering,2006,28(1):90-95.
[4] OSMAN N, SAIFUDDIN M, HALIM A. Contribution of Vegetation to Alleviate Slope’s Erosion and Acidity[G]//HERNEZ-SORIANO M C. Environmental Risk Assessment of Soil Contamination. London: IntechOpen Limited,2014:5772-5786.
[5] FAGERIA N K, STONE L F. Physical, Chemical and Biological Changes in the Rhizosphere and Nutrient Availability[J]. Journal of Plant Nutrition,2006,29(7):1327-1356.
[6] TISDALL J, OADES J. Stabilization of Soil Aggregates by the Root Systems of Ryegrass[J]. Australian Journal of Soil Research,1979,17(3):429-441.
[7] FEENEY D S, CRAWFORD J W, DANIELL T, et al. Three-Dimensional Microorganization of the Soil-Root-Microbe System[J]. Microbial Ecology,2006,52(1):151-158.
[8] BARRE P, HALLETT P D. Rheological Stabilization of Wet Soils by Model Root and Fungal Exudates Depends on Clay Mineralogy[J]. European Journal of Soil Science,2009,60(4):525-538.
[9] 言志信,宋杰,蔡汉成,等. 草本植物加固边坡的力学原理[J]. 土木建筑与环境工程,2010,32(2):30-34.
[10] GHESTEM Murielle, VEYLON Guillaume, BERNARD Alain, et al. Influence of Plant Root System Morphology and Architectural Traits on Soil Shear Resistance[J]. Plant Soil,2014,377(1-2):43-61.
[11] 肖宏彬,田青青,李珍玉,等. 林草混交根-土复合体的抗剪强度特性[J]. 中南林业科技大学学报,2014,34(2):1-5.
[12] 胡敏,李为萍,史海滨,等. 分布方式及根系径级对根-土复合体抗剪性能的影响[J]. 水土保持通报,2012,32(1):42-44.
[13] GENET M, STOKES A, SALIN F, et al. The Influence of Cellulose Content on Tensile Strength in Tree Roots[J]. Plant Soil, 2005, 278(1-2):1-9.
[14] MICKOVSKI S B, SONNENBERG R, BRANSBY M F, et al. Shear Reinforcement of Soil by Vegetation[J]. Millpress Science Publishers, 2007,3(4):24-27.
[15] MICKOVSKI S B, BENGOUGH A G, BRANSBY M F, et al. Material Stiffness Branching Pattern and Soil Matric Potential Affect the Pullout Resistance of Model Root Systems[J]. European Journal of Soil Science,2007,58(6):1471-1481.
[16] ENDO T, TSURUTA T. The Effect of Tree Roots upon the Shearing Strength of Soil[G]//Annual Report of the Hokkaido Branch. Tokyo: Government Forest Experimental Station, 1969:167-179.
[17] THOMAS R E, POLLEN-BANKHEAD N. Modeling Root-Reinforcement with a Fiber-Bundle Model and Monte Carlo Simulation[J]. Ecological Engineering, 2010, 36(1): 47-61.
[18] DOCKER B B, HUBBLE T C T. Quantifying Root-Reinforcement of River Bank Soils by Four Australian Tree Species[J]. Geomorphology,2018,100(3-4):401-418.
[19] MAO Z, SAINT-ANDRE L, GENET M, et al. Engineering Ecological Protection Against Landslides in Mountain Forests: Choosing Cohesion Models[J]. Ecological Engineering,2012,45: 55-69.
[20] 肖宏彬,赵亮,李珍玉,等.香根草根系的分布形态及抗拉强度试验研究[J].中南林业科技大学学报,2014,34(3):6-10.
[21] 宋维峰,陈丽华,刘秀萍. 林木根系固土作用数值分析[J]. 北京林业大学学报,2006,28(增刊2):80-84.
[22] 倪九派,袁天泽,高明,等.土壤干密度和含水率对2种紫色土抗剪强度的影响[J]. 水土保持学报,2012,26(3):72-77.
[23] NORMANIZA O,FAISAL H A,BARAKBAH S S. Engineering Properties of Leucaena leucocephala for Prevention of Slope Failure [J].Ecological Engineering, 2008,32(3):215-221.
[24] 格日乐,张成福,蒙仲举,等. 3种植物根-土复合体抗剪特性对比分析[J]. 水土保持学报,2014,28(2):85-90.
[25] 格日乐,左志严,蒙仲举,等. 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):72-77.
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