摘要
研究了5种模拟糙度和6种不同冲刷距离组合下3种粒径的红壤团聚体在集中水流内的剥蚀破坏规律,分析了糙度、运移距离以及相关水力学参数对团聚体剥蚀破坏的影响。结果表明,在相同运移距离条件下,随粒径和糙度的增加团聚体剥蚀破坏程度呈增加趋势,与粒径相比,糙度对剥蚀破坏程度的影响更大。相同模拟糙度下,随着运移距离的增加,剥蚀率均呈抛物线形先增大后减小的趋势;各运移距离下,7～5 mm粒径团聚体的剥蚀率随糙度的增加而增加;5～3 mm和3～1 mm粒径团聚体在各运移距离内随糙度的增加变化规律不一致。在不同糙度情况下,以运移距离等于36 m为例,团聚体与原始团聚体质量比（Wr/Wi）随径流水深、阻力系数、水流剪切力的增加均呈幂函数减小之后趋于平缓的趋势。该结果为研究红壤团聚体破碎理论机制提供了参考,对于完善土壤侵蚀过程模型,具有重要的理论意义。
【Objective】Soil aggregate is the basic unit of soil structure. Soil aggregates in runoff cause severe abrasion of soil surface,thus significantly affecting water infiltration rate of the soil surface,sediment transport and deposition,and development of soil erosion. With the aggregates breaking into numerous small particles,soil erosion starts. Researches have been reported illustrating that changes in roughness of the surface of a slope directly affect hydraulic characteristics of overland runoffs on the slope,like friction factor,flow depth and so on,which are the best hydraulic parameters to characterize aggregate erosion in the process of aggregate transport with runoff on the slope. Therefore,roughness of the surface of a slope may also affect disintegration of soil aggregates in runoff to a varying extent relative to degree of roughness. 【Method】In order to study erosive effect of soil aggregates in runoff on slopes different in surface roughness,an experiment was conducted in the artificial rainfall simulation lab of the Huazhong Agricultural University. The soil used in the experiment was Ultisols,collected from Xianning of Huibei Province,China. The soil sample was air-dried and oven-dried at 40℃ for 24 h to ensure that the soil sample was constant in moisture content. Before the experiment,portions of soil aggregates 20 g each were weighed out,0.0001 g in diversion,and were put separately in flasks containing ethanol（95%）for 10 min to expel air from the aggregates so as to eliminate the risk of breaking up the aggregates in the process of fast-wetting. Stainless steel flumes,adjustable in slope gradient,were set up. The pretreated soil samples were spread out in the flumes and prepared into 5 degrees of roughness（d=0,0.25~1,1~3,3~5 and 5~7 mm）separately. The flumes were adjusted to 10°in gradient and the water flow controlled at 0.4 L s-1.The experiment was designed to explore abrasion effects of soil aggregates in runoff as affected by particle size of the aggregates（7~5,5~3 and 3~1 mm）,roughness of the surface（d=0,0.25~1,1~3,3~5 and 5~7 mm）and transport distance（9,18,36,54,72 and 108 m）and effects of particle size,surface roughness,transport distance and some related hydraulic parameters（flow depth,friction factor,flow shear stress）on aggregate abrasion. 【Result】Results show that（1）aggregate abrasion aggravated with rising particle size of the aggregates,and with rising surface roughness,too,when transport distance remained the same. Yet,the effect of the latter was more obvious than that of the former. The effects of roughness and interaction of roughness and particle size all reached the significance level p〈0.05,regardless of transport distance,however,the effect of particle size was not significant when the transport distance reached 54 m or 72 m.（2）On slopes the same in roughness,abrasion rate followed a paracurve,rising and then falling with increasing transport distance. Regardless of transport distance,the abrasion rate of the aggregates,7~5 mm in particle size,increased with increasing roughness;but that of the aggregates,5~3 mm or 3~1 mm in particle size,varied irregularily with increasing roughness.（3）When the transport distance was fixed to be 36 m,Wr /Wi of aggregates declined as a power function of increasing depth of the runoff,regardless of roughness,which may be attributed to the joint effect of roughness and runoff depth,and the effect of roughness was more obvious in the case of the flow rate and slope gradient set in the experiment. Aggregate abrasion rate decreased as a power function of increasing friction factor and/or flow shear stress,declining first and then leveling off. However,in the case of varying roughness,the effect of runoff depth on abrasion rate of aggregates as affected by slope gradient and flow rate needs to be studied further. 【Conclusion】All the findings in this experiment may serve as reference for researchers in studying mechanisms of red soil aggregates breaking down in runoff and have some great theoretical significance to the development of proper soil erosion models.
出处
《土壤学报》
CAS
CSCD
北大核心
2016年第4期860-868,共9页
Acta Pedologica Sinica
基金
国家自然科学基金项目(41401303
41471231)资助~~
关键词
团聚体
集中水流
糙度
运移距离
水力学参数
Aggregate
Concentrated flow
Roughness
Transport distance
Hydraulic parameter
