聚丙烯酰胺对花岗岩砂土分离与产沙过程的影响

Effects of Polyacrylamide on Detachment and Sediment Production Process of Granite-derived Sandy Soil

[目的]探究聚丙烯酰胺(PAM)施用对花岗岩母质发育砂土分离与产沙过程的影响,明确PAM改良砂土抗蚀性的浓度阈值,为崩岗侵蚀防治提供依据。[方法]选取崩岗侵蚀区花岗岩母质发育的砂土,设置5个PAM施入水平(0‰,1‰,3‰,5‰,7‰),通过径流冲刷模拟试验,研究不同水力条件下砂土产沙速率、分离速率及细沟可蚀性对PAM施用浓度的响应规律。[结果]①PAM显著降低了砂土的产沙速率、分离速率和细沟可蚀性,且显著提高了临界剪切力(p<0.01)。PAM的减沙效应随冲刷时间的增加呈降低后稳定的趋势,而随其施用浓度的增加逐渐增大。当PAM施用浓度在5‰以内时平均减沙效果最明显。②土壤分离速率与PAM施用浓度呈极显著的负相关关系(p<0.001),但随着PAM施用浓度的增加,分离速率的降低速率逐渐减缓,且PAM(F=37.39,p<0.001)对土壤分离与产沙过程的作用大于水流剪切力(F=15.38,p<0.001)。③PAM处理组与CK的细沟可蚀性之比与PAM浓度呈二次函数关系(R2=0.996,p<0.001),且5‰的PAM对细沟可蚀性的降低效率最显著。[结论]施用PAM有效降低了花岗岩砂土的产沙速率、分离速率与细沟可蚀性,提高了其临界剪切力,改良效果在PAM施用浓度低于5‰时呈不断增加的趋势,而PAM施用浓度大于5‰时改良效果没有明显变化。因此,建议5‰为PAM改良花岗岩砂土抗蚀性的浓度阈值。

[Objective]The effects of Polyacrylamide(PAM)applicated in separation and sediment yield process of sandy soil developed from granite parent material were determined,and the concentration threshold of PAM to increase erosion resistance of sandy soil was clarified to provide a basis for the control of Benggang erosion.[Method]Sandy soil developed from granite parent materials in Benggang erosion areas was selected.Five levels of PAM application concentrations(0%,1%,3%,5%,7%)were set.Through runoff scouring simulation experiments,the response patterns of sediment yield rate,detachment rate,and rill erodibility of sandy soils to PAM concentration under different hydraulic conditions were studied.[Results]①PAM significantly reduced sediment yield,detachment rate,and rill erodibility,but dramatically increased critical shear strength(p<0.01).Additionally,the sediment yield reduction effect of PAM showed a decreasing and stabilizing trend with increasing scouring time,but gradually increased with increasing application concentration,with the most pronounced average sediment reduction effect observed when PAM concentration was within 5%.②There was a highly significant negative correlation between soil detachment rate and PAM application concentration(p<0.001).However,as PAM application concentration increased,the rate of decrease in soil detachment rate gradually slowed down,and the effect of PAM(F=37.39,p<0.001)on soil detachment and sediment yield processes was greater than the shear strength of runoff(F=15.38,p<0.001).③The ratio of rill erodibility between the PAM-treated groups and the control showed a quadratic function relationship with PAM concentration(R2=0.996,p<0.001),and the efficiency of reducing rill erodibility was most significant at 5%PAM.[Conclusion]The application of PAM effectively reduced the sediment yield rate,detachment rate,and rill erodibility of granite-derived sandy soil and increased its critical shear force.The improvement effect of PAM application showed a continuous increasing trend when the PAM application concentration was below 5%.However,when the PAM application concentration exceeded 5%,the improvement effect showed only a slight change.Therefore,5%should be considered as the concentration threshold for PAM to improve the erosion resistance of granite-derived sandy soil.