两种工程堆积体坡面细沟形态与产沙关系对比研究

A Comparative Study on Relationship between Rill Morphology and Sediment Yield on Slopes of Two Types of Engineering Mounds

为探究不同土壤类型工程堆积体坡面细沟形态与水动力学参数及侵蚀产沙间的关系,选取沟宽、沟深、宽深比等作为细沟形态参数,在放水流量8、12、16、20 L·min^(-1)和坡度32°条件下,对红土和塿土工程堆积体进行冲刷试验。结果表明:(1)两种堆积体坡面细沟沟宽、沟深在前24 min均发育迅速;随放水流量增大,沟宽和沟深均呈增大趋势,红土沟宽均值(较8 L·min^(–1))分别增加0.8%、19.3%、27.2%,沟深均值分别增加24.5%,126.2%,95.1%,而塿土则为3.7%、62.4%、108.2%和18.2%、87.9%、95.5%;红土沟宽、沟深与冲刷历时均呈极显著线性函数关系(R2>0.858,P<0.01),而塿土则为极显著对数函数关系(R2>0.689,P<0.01);(2)两种堆积体坡面细沟宽深比呈先波动(0~24 min)后(25~45 min)平稳的变化趋势;放水流量增至16 L·min^(-1),两种堆积体宽深比均值减幅最大(较8 L·min^(-1)),红土最大减少了1.15,塿土最大减少了0.20;(3)两种堆积体坡面细沟水流剪切力、水流功率与沟宽、沟深均呈现幂函数关系(R2>0.602,P<0.01);径流剪切力更适合描述红土沟深的发育状况,而径流功率更能体现塿土沟宽的发育过程;(4)两种堆积体坡面累计产沙量与沟宽和沟深均呈极显著线性函数关系(R2>0.897,P<0.01);沟宽、沟深对红土坡面累计产沙量的贡献率分别为84.9%、15.1%,对塿土则为22.5%和77.5%;该研究可为不同土壤类型工程堆积体坡面水土保持措施合理配置提供理论依据。

【Objective】Production and construction activities,like digging,excavating,dumping and piling-up of earth,form a large number of engineering mounds,which are ordinarily complex in underlying and surface structure and poor in erosion resistance.The mounds are mainly in the form of flat tops and slopes,whereon,rill erosion is easily occurring on slope surface with scouring flow running down from the top of the mound.In the process of rill erosion,rill morphology is closely related to hydrodynamic characteristics,and the relationship tends to be affected by soil texture.So it is essential to explore the relationships of slope rill morphology with hydrodynamic parameters,sediment yield and soil texture of the engineering mound.【Method】To that end,a field scouring-erosion experiment was carried out on an engineering mound of red soil and another of lou soil.Changes in rill morphology parameters,including rill width,rill depth and width-depth ratio,were monitored on slopes 32°in gradient,with scouring water flowing down at 8,12,16 and 20 L·min^(–1)(designated as TreatmentⅠ,Ⅱ,ⅢandⅣ),separately.【Result】Results show:(1)In the first 24 min,rill width and rill depth on the slope of the two kinds of engineering mounds developed rapidly.With increasing volume of the scouring water(8-20 L·min^(-1)),both exhibited a rising trend;compared with TreatmentⅠ,TreatmentⅡ,ⅢandⅣwas 0.8%,19.3%and 27.2%higher in mean rill width,and 24.5%,126.2%and 95.1%higher in mean rill depth,respectively,on the mound of red soil,and 3.7%,62.4%and 108.2%higher and 18.2%,87.9%and 95.5%higher,respectively,on the mound of lou soil.The relationships of rill width and depth with duration of scouring was statistically significant on the mound of red soil(R2>0.858,P<0.01),and of lou soil(R2>0.689,P<0.01),too;(2)Rill width-depth ratios on the two types of mounds both fluctuated during the initial period(0-24min)and then levelled off during the late period(24~45 min);compared with Treatment I,Treatment III was the lowest in mean width/depth ratio on either mound,being 115%lower on the mound of red soil and 20%lower on the mound of lou soil;(3)The relationships of runoff shear force and power of rill flow on slope surface with width and depth of rill could be described with a power function(R2>0.602,P<0.01);runoff shear force was a parameter more suitable for describing development of rill depth on the mound of red soil,and runoff power was for describing development of rill width on the mound of lou soil;and(4)Extremely significant linear function relationships were observed of cumulative sediment yield of the slope with rill width and rill depth(R2>0.897,P<0.01);rill width contributed 84.9%and rill depth did 15.1%to the cumulative sediment yield on the mound of red slope,and 22.5%and 77.5%,respectively,on the mound of lou soil.【Conclusion】This study may provide a theoretical reference for research on rill erosion mechanism on engineering mounds different in texture.