草被减流减沙效应及其力学机制分析

 利用人工模拟降雨试验,定量研究不同降雨强度下20°坡面草地的减流减沙效应,探讨草被坡面固土作用的力学机制。结果表明:在45、87和127mm/h降雨强度下,草地坡面土壤的平均入渗率是裸地坡面入渗率的2.1～4.2倍;与裸地相比,草地径流流速减少77.3%～79.8%,径流量减少51.9%～99.1%,产沙量减少93.6%～99.2%;从力学角度分析坡面土壤颗粒的受力情况,建立的坡面产沙量与径流切应力的关系模型可用于草被坡面土壤流失量预测;试验条件下,草地临界径流切应力值为2.857N/m2,裸地临界径流切应力值为0.861N/m2,坡面产沙量随径流切应力的增大而增大。研究结果对定量评价草被减流减沙作用和深化土壤侵蚀力学过程有一定的参考意义。

Reduction effects of grass on runoff and sediment and its mechanical mechanism

Reduction effects of grass on runoff and sediment as well as its mechanical mechanism was studied under rainfall intensities of 45, 87 and 127 mm/h on 20°grass slope using simulated rainfall experiment. The results showed that soil infiltration rate of grass slope was 2.1 - 4.2 times higher than that of bare slope. Flow velocity, runoff and sediment amount on grass slope decreased by 77.3% - 79.8%, 51.9% -99. 1% and 93.6% -99.2% respectively compared with those on bare slope. Relationship model between flow shear stress and sediment amount was built by analyzing of carrying force of soil partial, which can be used to predict the amount of soil loss on grass slope. The critical flow shear stress of 2. 857 N/m^2 on grass slope and 0. 861 N/m^2 on bare slope were measured based on the relationship model under experiment condition. The sediment amount increased with the increase of flow shear stress. The experiment results are meaningful for quantifying runoff and sediment reduction and deepening soil erosion mechanical process also.