基于两种计算模型的油松与元宝枫根系固土效能分析

目的]定量分析北方常见植物(油松、元宝枫)根系对提高土壤抗剪能力的作用,为更好地评价植物根系固土效能提供理论基础。方法]选取不同根系面积比(RAR)的油松(Pinus tabulaeformis)根土复合体、元宝枫(Acer truncatum)根土复合体及素土分别进行了不同垂直压力下的直剪试验,得出了油松根土复合体、元宝枫根土复合体及素土的抗剪强度增量。并通过根系的拉伸试验测定了植物根系的抗拉强度,同时使用Wu的根土复合体模型和Pollen的纤维束模型对抗剪强度增量进行模拟并与实际测定的抗剪强度增量进行对比分析。结果](1)根系主要通过增强土壤的黏聚力来增强土壤的抗剪切强度;(2)植物根系抗拉强度、拔出强度与根系直径都符合幂函数关系,抗拉强度和拔出强度大小存在阈值,根系大于2mm时,根系拔出强度小于根系抗拉强度,小于2mm时则反之;(3)Wu的根土复合体模型高估植物根系固土效果值平均为26.81%,而纤维束模型对根系提高土壤抗剪强度则平均高估9.82%。结论]相对于Wu模型,纤维束模型对土壤的固土效果的计算更为准确。

An Analysis on Soil Physical Enhancement Effects of Root System of Pinus Tabulaeformis and Acer Truncatum Based on Two Models

Objective] Analyzing the effects of two common plants' root system on improving soil shear resistance quantitively in order to provide some theoretical bases for the evaluation of soil enhancement effect of plant's root system. Methods] Direct shear and two kinds of model(Wu model, the fiber bundle model) were conducted to compare the shear strengths of root-soil composites with different RAR(root area ratio) of Pinus tabulaeformis and Acer truncatum with that of plain soil. A universal testing machine was used to measure the root's pull-out strength and tensile strength. Results] (1) Mainly through enhancing soil cohesion, roots could enhance soil shear strength; (2) The relationship between root strength(include tensile strength and pull-out strength) and root diameter agreed with power funnnction. When root diameter D > 2 mm, pull-out strength was less than tensile strength, and vice versa; (3) The Wu model overestimated the shear strength of root-soil composite at an average of 26.81%, and the fiber bundle model also overestimated with an average of 9.82%. Conclusion] As comparing to the Wu model, the fiber bundle model is more accurate in describing the effect of root's soil enhancement.