草类根系对坡面土强度及崩解特性的影响试验

坡面植被的固土防冲刷失稳作用往往取决于草类根系对坡面土强度和抗崩解特性的提高幅度。为研究草类根系对提高坡面土强度和抗崩解特性的影响规律，首先通过植草种植试验和观察，研究草类根系生长及竖向深度含根量分布规律，然后采用直剪试验得到不同根系含量或不同生长深度与根-土复合体强度的关系，并对添加不同含量根系的根-土复合体进行强度试验，比较种植活根系和添加死根系根-土复合体不同的强度特性。对路堑坡面植草根系原状土样和添加根系重塑配制土样进行崩解试验，比较分析坡面土壤的结构性、根系含量对植草坡面土体崩解特性的影响。结果表明：草类根系的纵横穿插与缠绕根网加筋作用使草类根系能显著增强根-土复合体的强度，种植根系的毛细根系及生物活性使其对土体强度提高的加筋效应远优于添加根系，其提高幅度与根含量呈线性增加关系；由于草类根系的缠绕包裹作用提高了土的强度，且草类根系在土体孔隙中的穿插能减少雨水入渗时的孔隙气压及封闭气体，从而使草类根系能显著提高根-土复合体的抗崩解特性；路堑边坡土体的结构性以及主根系衍生出大量毛细根系的存在，使添加根系重塑配制土的抗崩解能力远小于路堑边坡种植根系原状土；根土样在配制土中采用稻秸秆代替草类根系，在同样添加比例的情况下具有更高的抗崩解能力及加筋强度。

Experiment on Effect of Grass Root System on Slope Soil Strength and Disintegration Characteristics

The erosion resistance of slope plants and slope soil reinforcement usually depended on the enhancement of slope soil strength and its anti-disintegration properties caused by root-soil composites. In order to investigate the influence of grass roots on the strength and anti-disintegration properties of slope soil, ryegrass root growth and its vertical distribution were firstly investigated by dint of the cultivation test and observation. With the direct shear test, the relationship of the strength of root-soil composites, different root content and growth depth for planted roots was obtained. The strength test on root-soil composites with different root content was carried out to compare the strength characteristics of planted and grafted grass roots. In the meantime, disintegration tests on remolded grass-root soil samples and planted grass-root soil samples collected from the highway slope were conducted,and the effect of soil structure and root content on the disintegration characteristics of soil mass was analyzed.The results show that the reinforcement effect of crisscrossing and winding grass roots has significant impact on the enhancement of the strength of root-soil composites. As the capillary root and biological activity exist in the planted grass roots, the reinforcement effect of planted root is far superior to that of grafted root, and the soil strength shows a linear dependence on root content. On account of the reinforcement effect of crisscrossing and winding grass roots, the strength of soil is enhanced, and the pore pressure and closed gas during rainwater infiltration can be reduced by the grass roots in the soil pore penetration.Hence, the grass roots can significantly increase the anti-disintegration properties of the root-soil composites.Due to the structural nature of the cutting slope and a large number of capillary roots derived from the planted main roots, the anti-disintegration properties of original constructional soil are stronger than those of the remolded soil with grafted roots. By replacing grass roots with rice straw in the remolded soil, the strength of root-soil composites and their anti-disintegration properties can be remarkably improved.