三维土工网垫植草护坡防坡面径流冲刷的机制分析

基于水力学和河流动力学的基本原理，利用坡面糙率和拦污栅模型分别模拟三维土工网垫和坡面植被作用，建立了三维土工网垫和坡面植被引起的坡面沿程水头损失和径流局部水头损失计算式，并建立三维土工网垫植草护坡时坡面径流速度计算表达式，将颗粒启动速度引入分析坡面土颗粒流失初始的启动流速，进而通过坡脚流速和坡面土颗粒启动流速的对比分析和通过分析坡角、植株密度、网垫和植被类型对坡脚流速的影响来研究三维土工网垫植草护坡的防径流冲刷特性。结果表明，坡脚流速随坡角增大而增大；网垫类型对坡脚流速影响不明显，但同无护坡时相比网垫能显著降低坡脚流速；坡脚流速随植株和叶部倾角增加而变小，且随植株密度增大而减少，并在考虑不同边坡土质的颗粒启动速度与坡脚流速相等时计算得到护坡所需的植株最小密度。

Mechanism analysis of ecological slope protection against runoff erosion by grass jetting on 3D geomat

Combining with theories of hydraulics and river dynamics, numerical expressions of head loss resulting from different types of 3D geomat with roughness and local head loss of runoff resulting from grass are given respectively; and then formula calculating runoff velocity of slope surface for grass jetting on 3D geomat and toggling velocity of soil aggregate based on the theory of river dynamics are established. Furthermore, on the basis of calculation results, comparative analyses are made to examine effects of slope angles, types of 3D geomat, types of grass, and density of grass on runoff velocity of slope toe. The results show that the runoff velocity of slope toe increases with increase of slope angle; and types of 3D geomat do not affect significantly on runoff velocity, but can lower remarkably runoff velocity compared with non-slope protection; runoff velocity of slope toe decreases with increase of inclination angle for base and leaf of grass. In addition, the minimum density value of grass can be achieved by supposed to be equal of toggling velocity for soil and runoff velocity of slope toe. The results about mechanism of grass jetting on 3D geomat could be used to guide project practices.