崩岗洪积扇草本植物根系固土的力学特性研究

发布时间：2018-01-24 07:26

本文关键词： 崩岗洪积扇根系根土复合抗拉强度抗剪强度　出处：《福建农林大学》2017年硕士论文　论文类型：学位论文

【摘要】：为探讨草本植物根系对崩岗洪积扇土壤的固土力学特性,本文以巨菌草及宽叶雀稗为研究对象,采用根系拉根试验、原位剪切试验、室内直剪试验分析根系抗拉特性及根系对根土复合体抗剪强度的影响。研究结果如下:(1)草本及裸地的土壤自然含水率均随土层深度的增加而表现为递减的趋势,而各措施的土壤容重均随土层深度增加而表现为递增的趋势。巨菌草和宽叶雀稗的根系均主要分布在0—5 cm 土层,随着土层深度的增加,巨菌草各根系参数表现为对数函数形式降低,而宽叶雀稗的根系参数则表现为线性函数形式降低。两种草本植物均以0.5 mm径级根系为主,且巨菌草细根比宽叶雀稗细根更多。(2)根系直径与拉伸标距对根系极限抗拉力与抗拉强度的影响显著,而拉伸速率则对这两种草本植物根系的抗拉特性影响不显著。两种草本植物根系的单根极限抗拉力随直径的增加呈幂函数增加,而其单根抗拉强度则随直径的增大呈幂函数形式减小。宽叶雀稗根系的单根极限抗拉力与抗拉强度随标距增加而减小,但巨菌草根系在5 cm的标距下表现出最强的抗拉强度。当拉伸条件相同时,巨菌草极限抗拉力及抗拉强度高于宽叶雀稗,说明巨菌草较宽叶雀稗拥有更强抵抗外力拉伸的能力。(3)野外原位剪切试验表明,宽叶雀稗和巨菌草均能提高崩岗洪积扇土壤的抗剪强度,且巨菌草的效果更明显;随土层深度的增加,巨菌草的抗剪强度呈对数函数减小,而宽叶雀稗呈指数形式降低。在0—20 cm各土层,两草种抗剪强度均显著大于裸地。崩岗洪积扇土壤的抗剪强度与巨菌草及宽叶雀稗根系的生物量密度、根表面积密度和分叉数密度极显著正相关,与根长密度显著正相关。通过逐步回归分析可知,草本植物根系的生物量密度是影响崩岗洪积扇土壤抗剪强度的主导因子。室内直剪试验表明,在土壤条件相同的情况下,根系直径对根土复合体抗剪强度的影响不显著。随着根重密度的增大,根土复合体抗剪强度增大,但仅当根重密度达到一定值时,根系对增强土壤抗剪强度的效果才明显;根土复合体的内摩擦角和粘聚力也随根重密度的增大而增大。根面积比率能表征巨菌草和宽叶雀稗根土复合体抗剪强度的强弱。综上,巨菌草及宽叶雀稗根系均有增强崩岗洪积扇土壤抗剪强度的能力,且巨菌草强于宽叶雀稗。因此,这两种草本植物在崩岗侵蚀区值得推广。
[Abstract]:In order to study the soil mechanics characteristics of herbaceous root system on the soil of alluvial fan, the root pulling root test and in situ shear test were used to study the soil properties of giant fungi and paspalum paspalum. The tensile properties of root system and the effect of root system on the shear strength of root soil complex were analyzed by direct shear test in laboratory. The results are as follows: 1). The natural soil moisture content of herbaceous and bare land decreased with the increase of soil depth. The soil bulk density of each measure increased with the increase of soil depth, and the root system of megaterium and paspalum were mainly distributed in 0-5 cm soil layer, with the increase of soil depth. The root system parameters of macrobacillus decreased in the form of logarithmic function, while the root parameters of Paspalum grandii decreased in the form of linear function. The root system of the two herbaceous plants was mainly 0.5 mm diameter root system. And the fine root diameter and the extension distance of the fine root of megaterium were more than that of the fine root of Paspalum paspalum, and the effects of the diameter and the extension distance on the ultimate tensile strength and the tensile strength of the root system were significant. However, the tensile rate had no significant effect on the tensile properties of the two herbaceous roots. The single root ultimate tensile strength of the two herbaceous roots increased with the increase of the diameter. However, the single root tensile strength decreased with the increase of diameter, while the single root ultimate tensile strength and tensile strength decreased with the increase of the distance. But the root system showed the strongest tensile strength at a distance of 5 cm. When the stretching conditions were the same, the ultimate tensile strength and tensile strength of the giant grass were higher than that of paspalum paspalum. The results of field in situ shear test showed that both Paspalum grandifolia and Macrobacillus could improve the shear strength of the soil of flood fan. And the effect of giant fungus is more obvious. With the increase of soil depth, the shear strength of Giant fungus decreased as logarithmic function, while that of Paspalum grandifolia decreased exponentially in 0-20 cm soil layer. The shear strength of the two herbaceous species was significantly higher than that of bare land. The shear strength of the alluvial fan soil was positively correlated with the biomass density, root surface area density and branching number density of the root system of Giant fungus and Paspalum paspalum. Through stepwise regression analysis, the biomass density of herbaceous plant roots was the main factor affecting the shear strength of alluvial fan soil. The direct shear test in laboratory showed that the root biomass density of herbaceous plants was the main factor that affected the shear strength of alluvial fan soil. Under the same soil conditions, root diameter had no significant effect on the shear strength of root soil complex. With the increase of root weight density, the shear strength of root soil complex increased, but only when the root weight density reached a certain value. The effect of root system on strengthening soil shear strength was obvious. The internal friction angle and cohesive force of root soil complex also increased with the increase of root weight density. The ratio of root area can indicate the shear strength of the root soil complex. Both the root system of macrobacillus and paspalum grandifolia have the ability to enhance the shear strength of the toppling flood fan soil, and the giant grass is stronger than the paspalum. Therefore, these two herbaceous plants are worth popularizing in the area of collapse erosion.
【学位授予单位】：福建农林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S157.43

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