黄土堆积体植物篱减沙效益与泥沙颗粒分形特征研究

为探究植物篱措施对工程堆积体边坡的减流减沙效益及其对侵蚀泥沙颗粒分形维数的影响,以堆积体未防护边坡为对照,以不同放水流量对不同坡度堆积体植物篱防护边坡进行了放水冲刷试验。结果表明:与对照相比,植物篱边坡初始产流时间滞后100~500 s,其产流率、产沙率整体均较小,产流率在时间尺度上表现为间歇性波动上升;植物篱减流效率在4%~60%之间,减沙效率范围在15%~50%之间,减流减沙效率均随坡度和放水流量的增加呈幂函数形式减小;各处理侵蚀泥沙颗粒中粉粒均占主导地位,黏粒次之,砂粒含量最少。与对照小区相比,植物篱防护边坡侵蚀泥沙砂粒体积分数降低,黏粒和粉粒体积分数升高;黏粒富集率增加,砂粒富集率减小,泥沙颗粒分形维数增大。分形维数与黏粒和砂粒体积分数之间均呈极显著线性相关,侵蚀泥沙颗粒分形维数主要由黏粒体积分数决定。

Runoff and Sediment Reduction Benefit of Hedgerows and Fractal Characteristics of Sediment Particles on Loess Plateau Slope of Engineering Accumulation

As a kind of special landform unit, engineering accumulation is an important source of soil erosion. To explore effects of hedgerows on sediment particles fractal dimension on hillslope, and the runoff and sediment reduction effects of engineering measures, the field pouring water scouring experiments were designed for different inflow rates (35L/min, 45L/min and 55L/min) and slopes (24°, 28° and 32°) in six normal runoff plots (20m×5m). The results showed that the lagged time of initial runoff of hedgerow plots was 100~500s, and the runoff rate and sediment yield rate were less than those of the control plot. Runoff rate rose for intermittent fluctuations in time scale compared with the control plot. Hedgerow reduced the flow rate by 4%~60%, and decreased the rate of sediment by 15%~50%. Significant power function relationships of runoff and sediment reduction rate with slope and flow rate were observed, and the effect of sediment reduction was better than that of runoff reduction rate equation. Runoff sediment was dominant with silt particle, followed by clay. Compared with the control plot, the volume percentage of sand particle in sediment of the hedgerow plots was reduced. In contrast, the volume percentage of clay and silt was increased. Hedgerow plots clay enrichment rate was higher than those in the control plot, and the sand accumulation rate was less than the control plot. The fractal dimension of the hedgerow plots was bigger than that in control plots. The relationships between fractal dimension and the volume fraction of clay and sand were available for better fitting linear model, and fractal dimension of sediment erosion was mainly determined by the volume fraction of clay. The research results could provide some basic data for establishing the model of soil erosion of engineering measures under the condition of accumulation, and provide a theoretical reference for the optimal allocation to hedgerow slope.