水土保持研究

研究水库消落带2种典型固土护坡草本的单根抗拉力学特性,可为明确草本根系固土护坡的力学机制提供依据。以狗牙根(Cynodon dactylon)、苍耳(Xanthium sibiricum)2种草本植物为对象,通过室内单根拉伸试验,对比观测了不同根径级别条件下单根的抗拉力、抗拉强度、极限延伸率和弹性模量,分析了各力学特性指标与根径间的拟合关系,并探讨了单根拉伸试验过程中的应力—应变特征。结果表明:(1)狗牙根单根抗拉力平均值大于苍耳,在0.30～0.50 mm和0.90～1.00 mm根径范围内两者达到显著性差异(p<0.05),狗牙根单根抗拉力分别比苍耳的大28.06%和9.95%;(2)狗牙根单根抗拉强度平均值是苍耳的1.08倍,在0.40～0.50 mm和0.90～1.00 mm根径范围内两者达到显著性差异(p<0.05),狗牙根单根抗拉强度分别比苍耳大24.10%和18.72%;(3)2种草本单根抗拉力和单根抗拉强度随着根径增大,分别呈幂函数增长和幂函数降低关系;(4)2种草本单根均呈弹塑性材料特征,单根拉伸过程中的应力—应变关系表现为弹性变形、弹塑性变形、塑性变形和突然断裂4个变化阶段,单根弹性变形阶段的极限拉应力约占极限抗拉强度的50%～70%;(5)狗牙根单根极限延伸率显著大于苍耳(p<0.05),分别为(23.59±0.44)%和(14.54±0.38)%,与之相反,狗牙根单根弹性模量显著小于苍耳(p<0.05),分别为(474.79±13.82)MPa和(540.77±14.21)MPa。整体来看,草本单根抗拉力学特性与植物类型、根径大小密切相关,狗牙根单根抗拉力和单根抗拉强度均大于苍耳,其单根抵抗外界拉伸作用的能力强于苍耳,说明狗牙根具有更强的固土护坡能力。

To further explore the mechanics mechanism of herb species roots on soil reinforcement and slope protection in the reservoir riparian zone, the mechanical properties of single root tensile of two typical herbs on soil reinforcement and slope protection were studied. The typical herbs(i. e. Cynodon dactylon and Xanthium sibiricum), which were widely grown in the reservoir riparian zone, were selected as the samples of study. Under the condition of different root diameter levels, the mechanical properties of single root tensile(i. e. tensile force, tensile strength, limit extensile rate and elastic modulus)of two herbs in the reservoir riparian zone were measured via single root tensile test. Furthermore, the stress-strain characteristics of single root during the tensile process were further analyzed. The results showed that:(1)the average value of single root tensile force data of Cynodon dactylon was larger than that of Xanthium sibiricum; under the condition of 0.30～0.50 mm and 0.90～1.00 mm root diameter levels, the single root tensile forces of Cynodon dactylon were significantly 28.06% and 9.95% larger than those of Xanthium sibiricum, respectively (p<0.05);(2)the average value of single root tensile strength data of Cynodon dactylon was 1.08 times that of Xanthium sibiricum; under the condition of 0.40～0.50 mm and 0.90～1.00 mm root diameter levels, the single root tensile strengths of Cynodon dactylon were significantly 24.10% and 18.72% larger than those of Xanthium sibiricum, respectively(p<0.05);(3)with the increase of root diameter, the single root tensile force of two herbs significantly increased, and the single root tensile strength the significantly decreased. These relationships can both be well fitted by power function;(4)the stress-strain characteristics of single root of two herbs showed the characteristics of elastoplastic materials, and the stress-strain curves for two herbs could be divided into four stages: elastic deformation, elastic-plastic deformation, strain hardening and fracture failure; the ultimate tensile stress in the elastic deformation stage accounted for about 50%～70% of the ultimate tensile strength;(5)the single root limit extensile rate of Cynodon dactylon was significantly higher than that of Xanthium sibiricum(p<0.05), and the single root limit extensile rates of Cynodon dactylon and Xanthium sibiricum were(23.59±0.44)% and(14.54±0.38)%, respectively; on the contrary, the single root elastic modulus of Cynodon dactylon was significantly lower than that of Xanthium sibiricum(p<0.05), and the single root elastic moduli of Cynodon dactylon and Xanthium sibiricum were(474.79±13.82)MPa and(540.77±14.21)MPa, respectively; the single root tensile mechanical properties of herbs are closely related to plant types and root diameter. On the whole, the single root tensile force and the single root tensile strength of Cynodon dactylon are both greater than those of Xanthium sibiricum. The ability to resist external stretching of Cynodon dactylon single root is stronger than that of Xanthium sibiricum, suggexting that Cynodon dactylon has stronger ability of soil reinforcement and slope protection.