模拟降雨条件下弃渣体边坡不同防护措施的减水减沙效益

Study on Runoff and Sediment Reducing Effects of Erosion Control Measures on Slopes of Slag Dumps with Simulated Rainfall

采用野外人工模拟降雨方法,以未防护弃渣体边坡为对照,研究了1.0、1.5 mm min-1降雨强度条件下神府矿区种草和鱼鳞坑措施对偏土质、偏石质和煤矸石弃渣体产流产沙的调控作用。结果表明:(1)不同措施下3种弃渣体边坡径流率均在产流6~9 min后趋于稳定,产流过程中弃渣体边坡侵蚀速率均呈波动减小趋势,且未防护坡面减小趋势较防护更明显。(2)植草对偏土质、偏石质、煤矸石弃渣体减水和减沙效益分别为42.91%~51.21%、26.28%~55.20%、1 0.3 3%和9 7.5 4%~9 7.9 5%、4 1.8 7%~4 2.2 6%、7.8 0%;鱼鳞坑的减水和减沙效益则分别为:51.89%~72.72%、22.37%~42.92%、21.32%和98.41%~99.30%、94.90%~91.84%、39.50%。(3)鱼鳞坑措施对偏土质弃渣体的减水和减沙效益较种草分别提高8.98%~21.51%和0.46%~1.76%;种草措施对偏石质和煤矸石弃渣体的减水和减沙效益较鱼鳞坑措施分别提高3.91%~12.28%和0.28%~3.06%及10.99%和31.70%。(4)3种未防护弃渣体的侵蚀速率和径流率呈显著线性关系,种草和鱼鳞坑措施改变了坡面水沙关系,侵蚀速率和径流率相关性减弱或无显著关系。研究结果可为矿区弃渣体边坡生态恢复措施布设提供科学指导。

【Objective】The ecological and environmental problems caused by mining,especially coal mining,have aroused worldwide concerns and attention. It is,therefore,essential to explore rapid and effective ways to rehabilitate the ecological systems in the mining areas. 【Method】Outdoor simulation of rainfall events was conducted with rainfall intensity controlled at 1.0 mm min^-1 or 1.5 mm min^-1 on slopes,different in texture,1）earthy slope（more soil than rock）;2）rocky slope（more rock than soil）：and 3）slope of gangue,to evaluate effects of the erosion control measures,planting grass and digging fishscale pit. The two years old grass of Agropyron was formerly planted in the farmlands around the mining and transplanted on the slopes and the fish-scale pits dug temporarily. The rainfall simulator was a troughtype artificial simulator. When the nozzle is 3 m above the ground,the raindrops may reach the end point speed. Plots of the artificial slopes were 3 m×1 each in area and 35° in slope gradient. Before the start of the experiment,rainfall was calibrated in intensity until it reached 85% or higher in uniformity coefficient. During the rainfall events,runoff flow velocity was measured with the dye tracing method. During the first 3 minutes of rainfall,samples of runoff and sediment were gathered every minute,and after that once every 3 minutes. Sediment samples were oven-dried for weighing. 【Result】（1）Runoff leveled off in rate in 6 minutes after the initiation of runoff on all the three types of slopes,regardless of type of control measure. The erosion rate on the slope of gangue tended to fluctuate,while declining and the trend was more obvious than those on the protected slopes.（2）Planting grass reduced runoff by 42.91%~51.21%,26.28%~55.20% and 10.33% and sediment by 97.54%~97.95%,41.87%~42.26% and7.80%,respectively,on earthy slopes,rocky slopes and slopes of gangue,while digging fish-scale pits did by 51.89%~72.72%,22.37%~42.92% and 21.32% and by 98.41%~99.30%,94.90%~91.84% and 39.50%,respectively.（3）On earthy slopes,digging fishscale pits was 8.98%~21.51% and 0.46%~1.76%,respectively,higher in runoff and sediment reduction rate than planting grass,while on rocky slopesand slopes of gangue,planting grass was 3.91%~12.28% and 0.28%~3.06% higher and 10.99% and 31.70% higher,respectively.（4）On all the three types of slopes without protection measures taken,linear relationships（R^2 = 0.775,p〈0.01;R^2 = 0.649,p〈0.01;R^2 =0.450,p〈0.05）were found between erosion rate and runoff rate,but they were weakened or fading out altered when the protection measures were taken. 【Conclusion】All findings in this study may serve as scientific basis in guiding ecological restoration of slopes of gangue in the mining area.