不同初始含水率黄土雨滴溅蚀试验

Raindrop Splash Erosion Test of Loess with Different Initial Moisture Content

降雨特性、土质类型及其改良措施是影响土壤侵蚀的重要因素,为了给黄土高原地区土壤侵蚀防治及相关研究提供参考,以延安地区某边坡上更新统原状黄土为研究对象,制备原状、干燥、增湿3种圆柱体试样(初始含水率分别为14.5%、4.5%、33.6%),试验方案为2个雨滴直径(3.0、5.0 mm)、3个雨滴频率(10、50、100滴/min)、雨滴落差1000 mm、降雨历时60 min,利用自行设计的单雨滴溅蚀试验平台进行不同初始含水率黄土的雨滴溅蚀试验,结果表明:1)随着降雨历时延长,雨水从雨滴降落点不断向四周渗透扩散,在雨滴连续击溅作用下试样表面形成由小到大、由浅变深近似圆形的溅蚀坑;溅蚀坑深度随降雨历时延长而增大、随降雨强度提高而增大,不同初始含水率黄土试样溅蚀坑深度随降雨历时的变化趋势基本一致,大致可分为快速增长、持续强化、稳定渐变3个阶段。2)相同初始含水率条件下,试样溅蚀破坏直径和溅蚀扩散直径随降雨强度提高而明显增大;相同降雨强度条件下,干燥试样雨水入渗量和入渗范围较大,增湿试样溅蚀坑内的薄层积水使雨滴溅蚀破坏减弱;小雨情况下初始含水率较高的土体易被溅蚀,而强降雨情况下初始含水率较低的干土易被溅蚀。3)溅蚀扩散直径为溅蚀破坏直径的2.1~3.3倍,溅蚀破坏直径、溅蚀扩散直径和溅蚀量(体积)受土体初始含水率影响显著。

Rainfall characteristics,soil type and its improvement measures are the important factors affecting soil erosion.In order to provide references for the prevention and control of soil erosion in the loess plateau and its related studies,the pleistocene undisturbed loess on a slope in Yan’an was taken as the research object,the three cylinder specimens of original state,drying and humidification(initial moisture content is 14.5%,4.5%and 33.6%respectively)were prepared.The test scheme included 2 raindrop diameters(3.0 and 5.0 mm),3 rain-drop frequencies(10,50 and 100 drops/min),the drop of raindrops is 1000 mm and rainfall duration of 60 min.The self-designed single raindrop splash erosion test platform was used to conduct raindrop splash erosion test on loess with different initial moisture contents.The re-sults show that a)with the extension of rainfall duration,the rain from the drop point to the surrounding infiltration diffusion,under the con-tinuous impact of raindrops,the surface of the sample formed from small to large,from shallow to deep approximately circular splash pit.The depth of splash pit is increased with the duration of rainfall and increased with the intensity of rainfall.The variation trend of splash pit depth with the duration of rainfall is basically the same for loess samples with different initial moisture contents,which can be roughly divided into three stages of rapid growth,continuous strengthening and stable gradual change.b)Under the same initial moisture content,the splash ero-sion destruction diameter and splash erosion diffusion diameter of the samples increase obviously with the increase of rainfall intensity;Under the same rainfall intensity,the rainwater infiltration volume and infiltration range of dry samples are larger,and the thin layer of accumulated water in the splash pit of humidified sample weakens the raindrop splash damage.In the case of light rain,the soil with higher initial moisture content is prone to splash erosion,while in the case of a heavy rainfall,the dry soil with lower initial moisture content is prone to splash ero-sion.c)The splash erosion diffusion diameter is 2.1-3.3 times of the splash erosion destruction diameter,and the splash erosion destruction diameter,splash erosion diffusion diameter and splash erosion volume is significantly affected by the initial moisture content.