模拟降雨条件下塿土的溅蚀特征试验研究

溅蚀在破坏土壤表层结构的同时为后续侵蚀提供丰富材料,以黄土高原典型土壤塿土为试验用土,通过模拟降雨试验,根据溅蚀速率、溅蚀前后土壤颗粒组成及表面强度变化指标,系统研究塿土的溅蚀特征。结果表明,溅蚀速率随降雨历时呈现幂函数变化,分为迅速降低、缓慢降低、趋于稳定3个阶段。土盘表面松散颗粒及利于溅蚀的粒级范围内颗粒的消耗、团聚体破碎及超渗产生的水层消耗雨滴能量、结皮的形成和发育分别是3个阶段的主要影响因素。在90mm/h的雨强下,塿土颗粒富集与耗损的临界粒径是0.05mm,雨滴打击分离粒级0.05mm颗粒,富集迁移粒级0.05mm颗粒。当含水率相等时,降雨历时越长贯入深度越浅。塿土表面强度随降雨历时增加,0~30min是塿土结皮形成的关键时期。塿土溅蚀过程是表土颗粒组成不断变化和表面强度逐渐完善的过程。

Rain-simulated Experiment Study on the Splash Erosion Characteristics of Lou Soil

Splash broke soil surface structure and provided abundant material for subsequent erosion. Rainfall simulation experiments on Lou soil were performed to study its splash erosion characteristics. Using the rate of splash erosion, the soil particle composition before and after rain and the surface intensity to describe the splash erosion characteristics. Results indicated that the splash erosion process could bedivided into three stages according to splash erosion rate. First, the splash erosion rate decreased rapidly, splashed out particles were mainly the loose particles on the surface. Second, splash erosion rate decreased slowly, and the raindrop kinetic energy was mainly used to destroy the soil structure. Finally, the splash erosion rate became constant, the formation of compact layer composed by fine particles formed in aggregate made the splash erosion rate tend to be stable. Under the rainfall intensity of 90 mm/h, the threshold particle size of enrichment and consumption was 0.05 mm. If the particle size was more than 0.05 mm, the function of raindrop was separation. If the particle size was less than 0.05 mm, the function of raindrop was transport. When the moisture content was equal, the longer the rainfall duration the shallower the penetration depth of soil. The surface intensity of Lou soil was continuously increasing. With the rainfall duration, and 0 to 30 min was the critical period of crust formation. Splash erosion process of Lou soil was a process that surface soil particle composition changed constantly and surface strength improved gradually.