工程堆积体陡坡坡面径流侵蚀输沙动力过程试验研究

Scientifically understanding to the hydrodynamic mechanisms of soil erosion by overland flow on steep slope of engineered landforms has been a key issue which needs to be urgently solved in the context of production and construction. In the research project, the classification scheme for engineered landforms will be summarized and generalized, and standardized parameter as well as universal simulation models will be determined and constructed for simulation of underlying surface of typical engineered landforms. Therefore, variations in erodibility of different eroding surface materials (of varying soil-rock ratios) and hydrodynamic processes of soil erosion and sediment transport will be studied on simulated underlying surface of typical engineered landforms in steep slope via combined methods of laboratory- and field-scale simulated rainfall and runoff scouring experiments, based on Soil erosion fundamentals, Hydrology, Sediment movement dynamics, Hydrogeology, Theory of statistics. The study aims to develop simple calculation methods for quick quantification of erodibility eroding surface materials on engineered landforms, and reveal the dynamics mechanism of soil erosion and sediment transport by overland flow on engineered landforms in steep slope. The study will provide scientific basis and theoretical guidance for the perfection of soil and water conservation science, the improvement of optimized disposition for anti-erosion strategies, as well as the comprehensive promotion of soil erosion risk assessment and sediment control in production and construction areas.

科学认识生产建设项目工程堆积体陡坡坡面水蚀规律及其水动力学机理，是生产建设背景下进一步有效遏制工程堆积体水土流失所亟待解决的关键问题之一。本项目以六大研究区典型堆积体下垫面为研究对象，运用土壤侵蚀学、水文学、泥沙运动力学、统计学等学科理论，在概化总结堆积体分类体系、确定模拟下垫面仿真模型的标准化参数、构建具有普适性的堆积体仿真模型基础上，采用室内（外）模拟降雨和径流冲刷的方法系统研究典型工程堆积体仿真模拟下垫面的水蚀动力过程，分析不同土质（不同土石比）土壤可蚀性变化规律并建立工程堆积体土壤可蚀性快速简便的计算方法、阐明工程堆积体陡坡坡面径流输沙过程对不同水动力条件的响应机制、揭示堆积体边坡侵蚀过程的动力学机理，为完善水土保持学科和促进生产建设项目水土保持措施优化配置、全方位推动我国生产建设项目水土流失治理提供科学依据和理论指导。

针对目前工程堆积体土壤侵蚀机理及水保措施配置问题，本项目开展了堆积体陡坡坡面径流侵蚀输沙动力过程研究，通过室内（外）模拟试验获得如下结果：.利用六大区调查数据分析堆积体下垫面基本特征为：坡度、坡长均不符合正态分布及对数正态分布，边坡坡度平均33.5°，坡长平均4.99 m。.利用径流模拟试验分析坡面细沟流土壤剥蚀率与水动力学和床面形态之间关系得出，土壤剥蚀率与流量、坡度均呈幂函数关系，且坡度对土壤剥蚀率的影响更大。无量纲土壤剥蚀率与无量纲流速、切应力、单位水流功率均呈幂函数关系；无量纲土壤剥蚀率与无量纲流速、单位水流功率之间存在分区现象，与无量纲切应力之间不存在分区。土壤剥蚀率随跌坑发育系数和L/H的增加分别呈幂函数增加和减小趋势，说明床面形态越复杂、跌坑发育越成熟，土壤侵蚀越剧烈。.利用降雨、径流及降雨+径流双动力模拟试验分析动力条件对坡面土壤侵蚀影响得出，产沙率呈减小-稳定（40、50、70 mm/h）、减小-稳定-波动（100、120 mm/h）、波动减小（10-25 L/min）和剧烈波动（降雨+径流）4种变化趋势。40 和 50 mm/h雨强下坡面侵蚀主要为零星分布的小坑，70、100 和 120 mm/h雨强下主要为侵蚀沟和不连续的跌坎，且分布在坡面中下部。不同汇流强度条件下坡面侵蚀形态无明显差异，均以侵蚀沟为主。双动力条件下，坡面侵蚀形态均为冲沟，且对泥沙量的贡献大于径流量。.利用模拟试验分析间歇性冲刷对堆积坡面土壤侵蚀影响得出，间歇性汇流下细沟侵蚀过程主要经历4个阶段，即片蚀-细沟雏形-细沟沟网-小切沟。间歇性汇流下细沟平均宽度和平均深度均随汇流强度和冲刷场次的增加而增加，细沟平均深度增加的幅度大于平均宽度；细沟宽深比随汇流强度和冲刷场次的增加而减小。细沟密度随汇流强度的增加而增加，随冲刷场次的增加先增加后减小，10 L/min是细沟沟网发育的临界汇流强度（细沟累计长度和细沟密度最大）。沟网以平行格局为主而非树枝状。细沟横断面总体上呈“V 形”，符合典型细沟剖面特征。