不同胶结特性土壤坡面泥沙输移特征对侵蚀形态的响应

The movement forms, selective characteristics and transport capacity of sediment particles in the slope erosion not only depend on the rainfall energy and overland flow hydraulic properties, but also affected by the soil erosion evolution process and the intrinsic properties of soil. Presently, the influence mechanism of soil aggregate cement properties on sediment transport characteristics within different erosion pattern still not quite clear. Two kinds of parent material development of different weathering degree soil from the subtropical and tropical were selected. Based on the analysis of properties, indoor simulation and field plot experiments, specific objectives of this project were: to determine the quantitative effect of raindrop kinetic energy and hydraulic properties of rill flow on the sediment transport process from different cementation properties of soil; to explore the law and impact mechanism of hydrodynamic erosion factors and soil aggregate cement properties to sediment transport in the various pattern of slope erosion; to clarify the response mechanism of sediment transport process to the evolution of slope erosion. The development of the project will be helpful to deepen the understanding of the mechanism of the soil erosion process, and provide a theoretical basis for establishing an erosion model based on physical causes.

坡面侵蚀泥沙输移过程中颗粒的运动形式、分选规律以及输移能力不仅取决于降雨的能量和坡面流水动力学特性，还受土壤侵蚀形态演变过程和土壤内在性质的影响。目前土壤团粒胶结特性对不同侵蚀形态泥沙输移特征影响机理仍不十分清楚。本项目选取我国亚热带、热带两种母质发育的不同风化程度土壤为试验材料，通过性质分析、室内模拟和野外原位小区试验，明确雨滴动能和坡面细沟水流水动力学特性对不同胶结特性土壤坡面泥沙输移过程定量影响，探求水蚀动力因子与土壤团粒胶结特性对坡面各侵蚀形态中泥沙输移规律与影响机制，阐明泥沙输移过程对侵蚀形态演变的响应机理。项目的开展有助于深化对坡面土壤侵蚀过程机理的认识，同时为建立基于物理成因的侵蚀模型奠定理论基础。

土壤团粒的胶结特性对不同侵蚀形态泥沙输移特征影响机理仍缺乏深入系统的研究。本项目选取了不同胶结特性的土壤为研究对象，系统探究了降雨雨滴动能和坡面径流水动力学特性对不同胶结特性土壤坡面泥沙输移过程和特征的定量影响。结果表明，六种土壤胶结特性的不同导致了其孔隙结构在数量和形态上存在明显差异，其中有机碳和游离氧化铝对团聚体内部孔隙的发育发挥了积极作用，游离氧化铁抑制了小孔隙的发展，这些差异间接反映到团聚体稳定性上，表现为红壤的高团聚体稳定性和黄褐土的低团聚体稳定性。考虑其对坡面侵蚀过程造成的影响，发现六种胶结特性土壤的泥沙浓度和产沙率与团聚体稳定性的变化规律一致。综合孔隙特征因子构建PLSR模型可以揭示团聚体孔隙结构对团聚体稳定性和坡面侵蚀过程的相对重要性。不同质地重塑土壤中黏粒含量的变化对径流泥沙输移能力的积极影响随着径流侵蚀力的增加而增加，同时响应了侵蚀细沟的断面形态。引入土壤粘聚力将之与单位水流功率相结合作为复合预测因子，可以构建适宜不同土壤侵蚀速率和泥沙输移能力的预测模型。弱胶结粗质土壤的径流率和土壤侵蚀速率随降雨动能的增加呈线性增加，当考虑土壤黏粒含量时，幂函数关系可用于描述土壤侵蚀速率与降雨动能（或水流功率）之间的定量关系。泥沙中细颗粒富集，而粗粒的竭耗，导致了坡面表面出现影响侵蚀过程“粗质化”的覆盖层。项目的开展有助于深化对坡面土壤侵蚀过程机理的认识，同时为建立基于物理成因的侵蚀模型奠定理论基础。