摘要
天然聚合衍生物(NPD)是一种新型的高分子聚合物,是坡面土壤侵蚀化学调控措施所采用的一种新型材料,通过室内人工模拟降雨试验,以裸坡为对照,研究了不同NPD施加措施(撒施和喷施)及不同施加量(1.0,3.0,5.0g/m2)条件下径流流速特征以及对侵蚀产沙的影响。结果表明:(1)施加NPD的坡面径流流速随降雨历时的变化与裸坡一致,均呈先增大后逐渐趋于稳定的趋势,且流速随降雨历时的变化过程可用对数方程描述。撒施在1.0mm/min雨强下,延迟降雨初始产流时间8~19min,而喷施在3个雨强下,初始产流的时间整体上较裸坡提前1~2min;(2)与裸坡相比,施加NPD具有显著减小流速的效应,且雨强越大,减小流速的效应越差;施加不同剂量NPD减缓坡面径流流速的效益范围13.2%~54.3%。其中撒施3g/m2剂量和喷施5g/m2剂量对坡面径流流速的减小效应相对较好;(3)与裸坡相比,施加NPD具有显著的减沙效应,且减沙效应范围为30.6%~71.2%。无论是撒施还是喷施,整体表现为5g/m2计量的减沙效应最好。(4)裸土坡面的侵蚀模数对平均流速的响应关系与撒施和喷施NPD坡面的侵蚀模数对平均流速的响应关系皆可用对数方程表示,且撒施和喷施对流速的减小作用均大于减沙作用。
The natural polymer derivative(NPD)is a novel type of macromolecular polymer which is also a new material for the prevention of water and soil loss.This study adopted chemical regulation technique,which was a non-traditional method,to conserve water and soil.In order to explore the effects of NPD on the flow velocity and sediment yield in the soil erosion process on loess hillslopes,two applicable methods(dry spreading and spraying)and three applicable dosages(1,3 and 5 g/m2)of NPD were conducted at the rainfall intensities of 1.0 mm/min,1.5 mm/min,and 2.0 mm/min on the slopes with gradient of 15°,bare slope was set as control.The results showed that:(1)when NPD was applied in the soil surface,the flow velocity increased moderately in the first few minutes,and then gradually approached a steady state in the late stage of the rainfall events,of which trend was somewhat similar to that in the bare slope surface;the relationship between instantaneous flow velocities and time during a rainfall event could be described by logarithmic equation;compared with the bare slope,dry spreading and spraying significantly reduced the flow velocity;undersmall rainfall intensity,dry spreading delayed initial runoff time from 8 to 19 min,but initial runoff times of spraying were 1~2 min earlier than that on bare slope under three rainfall intensities;(2)compared with the bare slope,the application of NPD had the significant effect of reducing the flow velocity,and the greater the rainfall intensity was,the poorer the effect of reduction was;application different doses of NPD to reduce flow velocity ranged from 13.2%to 54.3%compared with the bare slope;among them,dry spreading dose of 3 g/m2 and spraying dose of 5 g/m2 were relatively good for reduction of the flow velocity;(3)the application of NPD had significant effect on sediment reduction,and the ranges of sediment reduction rates varied from 30.6%to 71.2%compared with the bare slope;Application of dose of 5 g/m2 had best effect on sediment reduction under dry spraying or spraying;(4)the response relationship of erosion modulus of bare slope to average flow velocity or the response relationship of erosion modulus of dry spreading and spraying NPD to average flow velocity all can be expressed by logarithmic equations;the effect of spreading and spraying on reducing the velocity of flow was more significant than that of sediment reduction.
引文
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