灌木柠条锦鸡儿根-黄土状盐渍土界面相互作用力学特性

Mechanical Properties of the Interface Interaction Between Caragana korshinskii Kom.Root and Loess-Like Saline Soil

为了进一步探讨西宁盆地黄土区灌木植物根系固土护坡力学效应,以区内优势灌木植物柠条锦鸡儿为研究对象,开展不同土体密度、含水量、含盐量和根径单因素变化条件下的单根垂直拉拔试验,探讨和分析了上述因素对灌木植物根-土界面相互作用力学特性的影响和作用机理。结果表明:在垂直埋深为25 cm及其他因素恒定的情况下,随着土体密度由1.20 g/cm^(3)增长到1.60 g/cm^(3),单根最大抗拔出力由(28.60±2.83)N增长至(114.33±7.17)N,呈指数函数增长趋势;随着土体含水量由6.00%增长到22.00%,单根最大抗拔出力由(152.80±10.07)N降低至(31.50±5.53)N,呈指数函数降低的变化趋势;随着土体含盐量由0.59%增长至2.00%,单根最大抗拔出力呈现出先增大后减小的变化趋势,在含盐量为1.00%时,单根最大抗拔出力达到峰值(61.20±0.94)N,且二者关系符合二次函数关系;在根径为2.74~9.57 mm范围内,随着单根平均根径的逐渐增大,单根最大抗拔出力由25.20 N线性增长至97.10 N。在此基础上,提出了垂直单根最大抗拔出力计算模型,并指出计算垂直单根最大抗拔出力所需的根-土界面综合黏聚力和综合摩擦角可通过根-土界面直剪试验获得。

In order to improve our knowledge of the mechanical effects of roots of shrub species on soil reinforcement and slope protection in loess region of Xining Basin,the dominant shrub Caragana korshinskii Kom.was selected as the study object,and the effects of the density,moisture content,and salt content of soil,and the root diameter on the friction characteristics of the root-soil interface and their mechanisms were analyzed and discussed via the single root vertical pull-out friction test(i.e.,one factor was varied at a time).The results indicate that when the vertical buried depth was 25 cm and other factors are constant,as the density of soil increases from 1.20 g/cm^(3) to 1.60 g/cm^(3),the maximum pull-out resistance of C.korshinskii single root exponentially increases from(28.60±2.83)N to(114.33±7.17)N;maximum pull-out resistance exponentially decreases from(152.80±10.07)N to(31.50±5.53)N,as the moisture content of soil increases from 6.00%to 22.00%;as the salt content of soil increases from 0.59%to 2.00%,the maximum pull-out resistance initially increases with salt content of soil and then decreases,and the turning point of the maximum pull-out resistance[(61.20±0.94)N]occurs when the salt content of soil is 1.00%,exhibiting a quadratic relationship;as the average root diameter increases from 2.74 mm to 9.57 mm,the maximum pullout strength linearly increases from 25.20 N to 97.10 N.On these bases,a calculation model of the maximum pull-out resistance of a single vertical root is defined.In addition,the comprehensive cohesion and friction angle between the root-soil interface which requires to calculate the maximum pullout resistance of the vertical single root can be obtained via the direct shear test of the root-soil interface.