暴雨气候下砂土边坡植被护坡模型试验研究

Investigation on effects of vegetations on stability of sandy slope by indoor rainfall model test

摘要:

为探究植被护坡固土机理,首先进行“裸露边坡”和“植被边坡”的室内模型暴雨对比试验,进一步对3种速生草本植物的护坡稳定性进行对比分析,结果表明:在植物生长过程中,生长曲线基本呈“S”型,根系深度约为植被地面高度的1.7~2.1倍；在相同降雨条件下植被护坡的持续稳定状态时间是裸露边坡的2倍多,并且裸露砂土边坡发生整体破坏时具有突发性、直线型的特点；在3种植物护坡试验中,根系的几何形态较为重要.其中,狗牙根(倒三角型根系)边坡的整体稳定性效果最好,其次是四季青(均匀型根系)边坡,高羊茅(锥形根系)边坡的稳定性效果最弱.植物的根系,在生长中可以分泌大量黏胶物质将周围细小的砂土颗粒黏接起来,众多根系相互缠绕形成根网,并在边坡表面可形成近22 cm厚的根-土复合体保护层结构,起到了明显的浅层固土加筋作用.此外,当降雨导致坑内积水时,四季青边坡的均匀型根系可以有效防止砂土边坡发生流塑性破坏,对于探索新型仿生支护工艺具有一定的启发性.

Abstract:

To investigate the stability mechanism of vegetations on sandy slope under rainfall, a comparative experiment between “exposed slope” and “vegetated slope” was conducted by indoor rainfall model tests. Then, three kinds of selected fast-growing vegetations (Chinese holly, Bermuda-grass, and festuca arundinacea) were planted on sandy slope to further analyze vegetation slope protection. It was found that the growth curves of the vegetations were nearly S-type during plant growth, and the root depths were about 1.7-2.1 times of the vegetation heights. Under the same rainfall condition, the steady state time of vegetated slope was two times more than that of exposed slope. The global failure of exposed sandy slope had the characteristics of suddenness and linearity. Root architectures of vegetations played an important role in slope stability. The rainfall model test results show that the overall stability of the sandy slope with Bermuda-grass was the best, followed by the Chinese holly, and then the festuca arundinacea, whose root architectures were inverted triangle, uniform, and cone, respectively. Meanwhile, the growing root could bind the surrounding fine sand particles by releasing viscose materials. Consequently, the roots of vegetations were intertwined together to form a root net, and a compacted root-soil composite protective layer structure of 22 cm in thickness was formed on the slope surface. Additionally, Chinese holly with uniform root architecture could effectively prevent the occurrence of the local flow-type failure near the slope toe in the case of ponding water at the slope base, which can help to explore new bionic support technologies.