土壤粒径对灌木植物根-土摩阻特性影响

Effect of Soil Particle Size on Root-Soil Friction Characteristics of Shrub Plants

为了系统性研究灌木植物根系的固土力学效应,探讨土体对根系的摩阻特性,以4种不同土壤粒径(原级配,1.0~2.0,0.5~1.0,<0.5 mm)和3年生的典型护坡植物种火棘及紫穗槐为研究对象,采用室内直剪的方式对根系进行根—土界面直剪摩擦试验。结果表明:(1)根—土及土—土界面的摩阻强度与垂直荷载呈明显的正线性关系;随土体粒径的增加,根—土及土—土界面的摩阻强度、摩擦系数、黏聚力和摩擦角均呈现下降趋势,且在相同粒径范围内,火棘根—土界面摩阻特性显著优于紫穗槐和素土;(2)根—土界面与素土界面的剪应力随位移的增长速率呈现先增大后减小的趋势;根—土界面剪应力与位移关系曲线呈现曲折蜿蜒式上升,而素土曲线表现为平缓式上升;(3)土体粒径越小,根土间接触面的比表面积越大,细小的土壤颗粒与根表面发生镶嵌,加大接触面的咬合力,使摩阻能力加大。研究结果对进一步探讨灌木植物根—土相互作用力学机制,以及利用灌木植物提高试验区边坡土体稳定性、防治坡面浅层滑落具有一定的理论指导意义。

In order to systematically study the mechanical effect of shrub roots on soil consolidation and explore the friction characteristics of soil to roots,taking four different soil particle sizes(<2.0,1.0~2.0,0.5~1.0 and<0.5 mm)and three-year-old typical slope protection plants,Pyracantha fortuneana and Amorpha fruticosa,as the research objects,the direct shear friction test of root soil interface was carried out in laboratory.The results showed that:(1)The friction strengths of root-soil and soil-soil interface were positively related to the vertical load.With the increasing of soil particle size,the friction strengths,friction coefficients,cohesions and friction angles of root-soil and soil-soil interface all decreased,and within the same particle size range,the friction characteristics of P.fortuneana root soil interface were significantly better than those of A.fruticosa and plain soil.(2)The shear stress of the root soil interface and the plain soil interface increased first and then decreased with the increasing of displacement.The relationship curve of root soil interface shear stress and displacement showed a zigzag rise,while the plain soil curve showed a gentle rise.(3)The smaller the soil particle size was,the larger the specific surface area of the indirect contact surface between the root and soil was.The small soil particles inlayed with the root surface,which increased the bite force of the contact surface and increased the friction capacity.The above research had a certain theoretical significance for further exploring the mechanical mechanism of root soil interaction of shrub plants,and improving the stability of slope soil in the experimental area by use shrub plants and preventing the shallow sliding of slope.