| 花棒沙柳根与土及土与土界面直剪摩擦试验与数值模拟 |
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| 引用本文： | 田 佳,曹 兵,及金楠,赵元宵,李才华,郭 婷.花棒沙柳根与土及土与土界面直剪摩擦试验与数值模拟[J].农业工程学报,2015,31(13):149-156. |
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| 作者姓名： | 田 佳 曹 兵 及金楠 赵元宵 李才华 郭 婷 |
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| 作者单位： | 1. 宁夏大学农学院，银川 750021;,1. 宁夏大学农学院，银川 750021;,2. 北京林业大学水土保持与荒漠化防治教育部重点实验室，北京 100083;,1. 宁夏大学农学院，银川 750021;,1. 宁夏大学农学院，银川 750021;,1. 宁夏大学农学院，银川 750021; |
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| 基金项目： | 宁夏自然科学基金资助项目（NZ13009）；公益性行业科研专项经费项目（201304311） |
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| 摘 要： | 花棒和沙柳是毛乌素沙地中分布最广泛的优良防风固沙树种,在固定流动沙丘和半流动沙丘上效果明显。为了探索花棒和沙柳根-土界面的摩擦特性,该文选取毛乌素沙地5 a生人工种植花棒、沙柳的根系为研究对象,通过直剪摩擦试验研究界面类型、土壤含水率和垂直荷载对花棒、沙柳根-土界面以及素土-素土界面摩擦特性的影响,并采用有限元软件对直剪摩擦试验进行数值模拟。结果表明:花棒和沙柳根系对土壤抗剪强度的提高作用与根-土界面的黏聚力无关,与摩擦角有关。花棒根-界面的摩擦角显著高于素土-素土和沙柳根-土界面(P0.05)。土壤含水率的变化对根-土界面的黏聚力与摩擦角的影响规律相似,旱季和雨季对根系提高土壤抗剪强度的作用有显著影响(P0.05)。根-土界面的抗剪强度与垂直荷载的关系同样满足莫尔-库伦准则,本构关系为双曲线。花棒根-土界面抗剪强度极显著高于素土-素土界面和沙柳根-土界面(P0.01),从抵抗根-土位移的角度,花棒的固沙效果优于沙柳。该文所采用的应力、位移边界条件和Coulomb摩擦模型,模拟计算的根-土界面和素土-素土界面的抗剪强度与试验结果基本一致(最大相对误差10%),因此根-土界面的直剪摩擦试验可以通过本文所建立的有限元数值模型来模拟。研究结果可为根系固土作用的理论研究和防风固沙树种的筛选提供参考。
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| 关 键 词： | 摩擦 土 界面 数值分析 根 直剪摩擦试验 花棒 沙柳 |
| 收稿时间： | 2015/1/29 0:00:00 |
| 修稿时间： | 2015/6/13 0:00:00 |
Direct shear friction test and numerical simulation of soil-soil and root-soil interface of Hedysarum scoparium and Salix psammophila |
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| Tian Ji,Cao Bing,Ji Jinnan,Zhao Yuanxiao,Li Caihua and Guo Ting.Direct shear friction test and numerical simulation of soil-soil and root-soil interface of Hedysarum scoparium and Salix psammophila[J].Transactions of the Chinese Society of Agricultural Engineering,2015,31(13):149-156. |
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| Authors: | Tian Ji Cao Bing Ji Jinnan Zhao Yuanxiao Li Caihua and Guo Ting |
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| Institution: | 1. Agriculture School of Ningxia University, Yinchuan 750021, China;,1. Agriculture School of Ningxia University, Yinchuan 750021, China;,2. Key Lab of Soil and Water Conservation and Desertification Combating, Ministry of Education, Beijing Forestry University, Beijing 100083, China;,1. Agriculture School of Ningxia University, Yinchuan 750021, China;,1. Agriculture School of Ningxia University, Yinchuan 750021, China; and 1. Agriculture School of Ningxia University, Yinchuan 750021, China; |
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| Abstract: | Abstract: Hedysarum scoparium and Salix psammophila have obvious effect on the fixation of mobile and semi-mobile dunes in the Mu Us Desert. In order to explore the friction characteristics between root and soil, 5-year-old Hedysarum scoparium and Salix psammophila roots were measured in the laboratory. The influences of different conditions such as species, soil moisture and vertical load were examined by using direct shear friction tests in the study. The finite element software was used to simulate the process of the laboratory experiments. The results showed that the cohesion stress of the root-soil interface of Hedysarum scoparium and Salix psammophila had a significant difference (P < 0.05). However, there was no significant difference between Hedysarum scoparium root-soil interface and soil-soil interface (P > 0.05). The cohesion stress of the root-soil interface of Salix psammophila and soil-soil interface had a significant difference (P < 0.05). The cohesion stress of the root-soil interface of Hedysarum scoparium ((1.51±0.65) kPa) was higher than that of Salix psammophila ((-0.92±0.50) kPa), and the cohesion stress of soil-soil interface ((3.22±0.55)kPa) was also higher than that of Salix psammophila. The friction angle of the root-soil interface of Hedysarum scoparium had a significant difference with Salix psammophila (P < 0.05) and it also had a significant difference with soil-soil interface (P < 0.05). However, there was no significant difference between Salix psammophila root-soil interface and soil-soil interface (P > 0.05). The friction angle of the root-soil interface of Hedysarum scoparium ((31.00±0.14)°) was higher than that of soil-soil interface ((30.30±0.25)°) and Salix psammophila((30.20±0.17)°). There was a significant difference between the cohesion stress and the friction angle of the root soil interface (P < 0.05) under 2% (dry season) and 22% (rainy season) soil moisture. However, there was no significant difference under 7%-17% soil moisture (P > 0.05). The cohesion stress of 2% soil moisture ((0.0021±0.34) kPa) was lower than that of 22% soil moisture ((3.16±0.57) kPa). The friction angle of 2% soil moisture ((29.80±0.38)°) was lower than that of 22% soil moisture ((30.92±0.59)°). The relationship between vertical load and shear strength of the root-soil interface obeyed the Mohr-Coulomb theory and the constitutive relation was hyperbola. The maximum relative error of the shear strength simulated by the finite element software was 9.54%. The results of the study indicated that the improvement of shear strength of the root-soil composite was not related to the cohesion stress but related to the friction angle. The shear strength of the root-soil interface of Hedysarum scoparium was stronger than that of soil-soil interface and Salix psammophila (P < 0.01). The change of soil moisture had a similar influence on the cohesion stress and the friction angle of the root-soil interface. The capacity of improving shear strength of soil by root reinforcement was significantly affected by the dry and rainy season (P < 0.05). The process of the direct shear friction tests of root-soil and soil-soil interface could be simulated by the finite element model established in the study. The simulation results were consistent with the laboratory tests. The results of this research can serve as a basis for the further studies on the friction characteristics of root-soil interface and root reinforcement. This study also can provide a reference for the selection of windbreak and sand-fixation tree species. |
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| Keywords: | friction soils interfaces numerical analysis roots direct shear friction test Hedysarum scoparium Salix psammophila |
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