Tensile Strength of Root and Soil Composite Based on New Tensile Apparatus
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摘要:
为了研究植物根系在阻止边坡土体开裂中的作用机理，通过自主研制的一套单轴拉伸试验装置（由加载模块、数字控制模块、数据采集模块、制样模具4部分组成，可准确地获取测试材料的全过程位移-拉应力关系曲线和抗拉强度）定量地研究根系对土体抗拉强度的增强作用. 使用所研制的拉伸装置开展了不同含根量下灌木植物胡枝子根-土复合体的直接拉伸试验，分析根-土复合体的拉伸破坏机理，试验结果表明：素土的位移-拉应力曲线表现为单峰型，而根-土复合体的曲线表现为双峰型；随着含根量的增加，根-土复合体的抗拉强度呈非线性增大特征，相较于素土增加28.01%～142.15%；根-土复合体的抗拉强度可用本文提出的计算模型进行估算，当含根量为1～3根时平均误差为12.12%. 胡枝子根-土复合体的拉伸破坏过程可以分为4个阶段：应力增加阶段、土体破坏阶段、应力再增加阶段和根系滑移阶段，且根系主要在第一阶段和第三阶段起到贡献作用.
Abstract:In order to study the mechanism of plant roots in preventing slope soil cracking, a self-developed uniaxial tensile test device was used to quantitatively study the strengthening effect of roots on the tensile strength of soil and analyze the tensile failure mechanism of root-soil composite. The test device consists of a loading module, a digital control module, a data acquisition module, and a sample making mold, which can accurately obtain the entire process displacement-tensile stress relationship curve and the tensile strength of test material. A series of direct tensile tests were carried out on the root-soil complex of the shrub plant
Lespedeza bicolor under different root contents by the developed tensile device. The results show that the displacement-tensile stress curve of pure soil is unimodal, while the curve of root-soil complex is bimodal. The tensile strength of root-soil composite increases nonlinearly with the increase of root content, which is 28.01%−142.15% higher than that of plain soil. The tensile strength of root-soil complex can be estimated by the calculation model proposed in this paper. When the root content is 1−3, the average error is 12.12%. The tensile failure process of the root-soil complex can be divided into four phases: stress increase phase, soil failure phase, secondary increase stage, and root slip phase. The root system mainly contributes to the first and third stages.-
Key words:
- uniaxial tension test /
- test device /
- root and soil composite /
- tensile strength /
- root content
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图 6 根-土复合体位移-拉应力关系
Figure 6. Relationship between displacement and tensile stress of root-soil composite systems
图 7 第一峰值和第二峰值随含根量变化曲线
Figure 7. Variation curves of the first peak and the second peak with root content
图 8 抗拉强度增量计算值与试验值对比
Figure 8. Comparison between calculated value and test value of tensile strength increment
图 9 根-土复合体位移-拉应力典型关系曲线
Figure 9. Typical relationship of displacement and tensile stress of root-soil composite system
图 10 素土和根-土复合体的破坏形态
Figure 10. Failure modes of plain soil and root soil composite system
图 11 国道318德格—甘孜段浅层滑坡
Figure 11. Shallow landslide in Dege—Ganzi section of National Highway 318
表 1 试验用土体的物理力学参数
Table 1. Physical and mechanical parameters of test soil
参数 密度/（g•cm−3） 天然含水率/% 液限/% 塑限/% 黏聚力/kPa 内摩擦角/（°） 土质类型 数值 1.65 24.68 35.7 18.2 6.25 19.78 黏土 
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