Supported by the National Natural Science Foundation of China ( No. 41671276)
为明确鱼鳞坑坡面抗侵蚀演化过程及其水流水力学特性，采用间歇性人工模拟降雨实验，对鱼鳞坑坡面水流水力学特性以及阻力规律进行了系统分析。结果表明：（1）鱼鳞坑坡面侵蚀演化过程表现为：雨滴溅蚀—片蚀—股流冲刷—跌坑—细沟侵蚀—下切侵蚀—溯源侵蚀—崩塌。（2）随着降雨历时的增加，由于鱼鳞坑的层层拦截与蓄满，其下方的坡面径流流速、水深均呈波动式增长趋势，坑内出现旋涡，坡面径流呈现断续股流。降雨累积历时为58 min左右，总降雨量达到87 mm时，鱼鳞坑侵蚀量急剧增加，拦蓄径流作用失效。（3）五场降雨过程中，上坡和中坡水流流态为层流，下坡由于鱼鳞坑蓄满后径流出现波动，水流流态由层流变为紊流且时而为缓流时而为急流。（4）鱼鳞坑坡面水流阻力来源于降雨阻力、颗粒阻力、形态阻力叠加，在整个降雨过程中阻力总和呈下降趋势；其中，受地形高低起伏、地表糙度的影响，形态阻力一直居于主导地位。
【Objective】Fish-scale pits measure is a widespread and typical soil and water conservation engineering measure in Loess Plateau that can be used to impound runoff and reduce the soil erosion mass and create a good water condition for vegetation growth. In order to clarify erosion evolution processes and flow hydraulic characteristics of fish-scale pies measure under the condition of continuous rainfall. 【Method】In this paper, we analysed the erosion evolution with 3D laser scanner and realized graphical and digital process of erosion evolution on fish-scale pies slope by laboratory five rainfalls simulation. 【Result】The results showed that: (1)Dynamic process of fish-scale pits erosion could be presented as splash erosion－sheet erosion－drop pit－rill erosion－longitudinal erosion－headward erosion－collapse. By the end of the 5th rainfall, the largest rill length、width and depth respectively increased to 80 cm、22 cm and 7.8 cm. During the first two rainfalls, fish-scale pits played a significant role in water storage and silt detention, sheet erosion and rill erosion occurred at some parts of slope; Later, due to excessive water of pits and high moisture content of side slope, leading to collapse phenomenon in pits and longitudinal erosion, rill headward erosion at down-slope, also increased erosion. (2) As the rainfall duration increases, the down-slope velocity and runoff depth were increased with fluctuation because the rainfall could be hold up in pits. What’s more, vortex accurred in pits and streams scour accurred in slope surface.The order of the average flow velocity and the average water depth is: the up-slope>mid-slope>down-slope. The velocity and depth in rill were significantly larger the slope. The Reynolds number of up-slope and mid-slope was less than 500, and for down-slope, it was over 500 at the end of 5th rainfall. When rainfall accumulated duration reached 58 min and rainfall increased to 87 mm, erosion increased dramatically. Fish-scale pits unable to played a positive effect. (3) During five rainfalls, the upslope and mid-slope flow regime was laminar flow. With the down-slope pits being filled, slope runoff fluctuated greatly, down-slope flow became turbulent flow from laminar flow and changed between subcritical flow and supercritical flow. (4) Resistance mainly comes from rain, grain and form resistance, and form resistance that orginated from the rugged slope was the dominant resistance. Due to the callapse、scour and fluctuant change of terrain, resistance decreased with rainfall accumulation duration accompanied by minor fluctuations. The order of resistance was form resistance> grain resistance> rain resistance.【Conclusion】The study was of momentous significance to clarify the fish-scale pit slope erosion and its mechanism, also provides theory basis and decision support for loess plateau area to layout fish-scale pits reasonably. Only if we layout fish-scale pits reasonably in Loess Plateau area can we improve and keep soil moisture greatly.
郭慧莉,孙立全,吴淑芳,李宜坪,张永东.黄土高原地区鱼鳞坑坡面侵蚀演化过程及水力学特征[J].土壤学报,2017,54(5):1125-1135. DOI:10.11766/trxb201702210617 GUO Huili, SUN Liquan, WU Shufang, LI Yiping, ZHANG Yongdong. Erosion evolution processes and hydraulic characteristics analysis of fish-scale pit slop on Loess Plateau Region[J]. Acta Pedologica Sinica,2017,54(5):1125-1135.复制