暴雨作用下排土场边坡水土保持工程措施的减流减沙效益

Research on sediment reduction benefits of engineering measures on waste rock slope under different rainfall intensities

  • 摘要: 露天煤矿排土场具有坡度较陡、结构松散、稳定性较差等特点,在暴雨作用下水土流失强度较大,以往采用布设植物篱等的方法对控制边坡水土流失具有积极作用,但植被在未达到预期覆盖度前边坡的土壤侵蚀依然严重,而采取水土保持工程措施相较采取植物措施的施工时间短,且竣工后即可达到最大水土保持效益,进而达到快速控制水土流失的目的。为探明不同雨强作用下水土保持工程措施(水平沟、土工袋)对排土场边坡产流产沙的影响,以海州露天矿排土场边坡几何参数为基础构建排土场模型,并布设水土保持措施,基于阜新当地暴雨强度式计算值,以设计重现期50 a、降雨历时45 min为参数,设置降雨强度为60、90和120 mm/h,结合室内人工模拟降雨的方式,选取径流率、产沙量、减流效益和减沙效益等因子分析排土场工程措施控制侵蚀的效益。结果表明:① 不同雨强下,采取水土保持工程措施显著减弱了坡面径流的生成,增强了边坡的抗蚀能力,径流率相较对照组最多降低65.18%,产沙量相较对照组最多降低92.23%,低密度土工袋覆盖措施的减流减沙效果均优于其他工程措施。② 以降雨强度为60 mm/h时的对照组产流率、平均产沙量为基准值,窄埂水平沟组、低密度土工袋覆盖组、高密度土工袋覆盖组的产流率、平均产沙量2项指标与雨强均呈等比例增长。③ 产沙量与径流功率之间的关系在不同水土保持工程措施下存在差异,但总体而言,通过径流功率预测边坡产沙量更为合理。在无水土保持工程措施和宽埂水平沟处理下,径流率与产沙量的线性关系较强且成正比,这表明在没有水土保持工程措施或措施较弱的情况下,径流率的增加直接导致产沙量的增加;采取窄埂水平沟和不同密度土工袋覆盖的措施后,径流率与产沙量之间的线性关系显著减弱,从而说明水土保持工程措施的实施有效地减弱了径流率对产沙量的直接影响。采取水土保持工程措施后,边坡的水流动力学特性发生了变化,该措施影响了边坡水流的径流剪切力和径流功率,进而影响产沙量;而水平沟则通过分散水流和减缓流速,降低了边坡水流的径流剪切力和径流功率,从而降低了产沙量。

     

    Abstract: The dump slope of open-pit coal mines is characterized by steep gradients, loose structure, and poor stability, leading to severe soil erosion under heavy rainfall. While past methods like vegetative hedges have shown some effectiveness in erosion control, soil erosion remains significant before vegetation reaches the desired coverage. In contrast, soil and water conservation engineering measures (SWCEMs) require shorter construction time and achieve immediate maximum benefits upon completion, enabling rapid erosion mitigation.To investigate the influence of SWCEMs (horizontal ditches, geotextile bags) on runoff and sediment yield under varying rainfall intensities, a dump slope model was constructed based on the geometric parameters of Haizhou open-pit mine’s dump slope. Rainfall intensities of 60, 90, and 120 mm/h were set according to the local storm intensity formula in Fuxin (50-year return period, 45-minute duration). Indoor artificial rainfall simulations were conducted, and factors including runoff rate, sediment yield, flow reduction benefit, and sediment reduction benefit were analyzed to evaluate erosion control efficacy. ① Under varying rainfall intensities, SWCEMs significantly reduced slope runoff generation and enhanced erosion resistance. The maximum reductions in runoff rate and sediment yield compared to the control group were 65.18% and 92.23%, respectively. Low-density geotextile bag cover outperformed other measures in both flow and sediment reduction. ② At 60 mm/h rainfall intensity, the runoff rate and sediment yield of narrow-ridge horizontal ditches, low-density geotextile bags, and high-density geotextile bags increased proportionally with rainfall intensity, using the control group’s baseline values as reference. ③ The relationship between sediment yield and runoff power varied across measures, but runoff power provided a more robust predictor of sediment yield overall. Under no measures or wide-ridge horizontal ditches, runoff rate and sediment yield exhibited a strong linear proportionality, indicating direct causality. However, narrow-ridge horizontal ditches and geotextile bags weakened this relationship, demonstrating their efficacy in decoupling runoff from sediment transport. By dispersing flow and reducing velocity, SWCEMs lowered runoff shear stress and power, thereby mitigating sediment yield.The findings underscore the critical role of appropriate selection and design of SWCEMs in dump slope erosion control, offering a scientific basis for deploying targeted mitigation strategies.

     

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