【作者】 王瑄；

【导师】 李占斌；

【作者基本信息】 西安理工大学 ， 水利工程， 2008， 博士

【摘要】 坡面侵蚀是水力侵蚀的重要组成部分，其发生发展过程是土壤侵蚀动力机制研究的核心内容，也是水土流失防治和土壤侵蚀物理模型建立的关键所在。本研究针对坡面径流分散、剥离、输移和沉积过程的关键环节，采用变坡土槽放水冲刷试验方法，结合稀土元素（REE）复合示踪技术和坡面流速、径流宽、水沙等的观测，运用灰色关联和回归分析等方法，系统地分析了坡面侵蚀动力与侵蚀产沙的时空变化规律，阐明了坡面侵蚀产沙与水蚀动力因子之间的动态响应过程，揭示了土壤剥蚀率与沿程水蚀动力参数及含沙量之间的动态响应关系，建立了坡面土壤剥蚀率的计算模型。主要取得了如下结论：（1）阐明了径流冲刷条件下主要水蚀动力参数和坡面侵蚀产沙特征的时空变化规律。在放水冲刷试验条件下，坡面水流流态特征和动力特征表现为：坡面径流沿程雷诺数、水流剪切力和水流功率逐渐减少；沿程佛汝德数和流速逐渐增加；径流剪切力和径流功率随时间增加有增大的趋势；其侵蚀产沙特征表现为坡面上部土壤侵蚀最为剧烈，是坡面侵蚀产沙的主要来源。从坡上到坡下，各坡段产沙量占总产沙量的百分比急剧减少；产沙量沿土层深度方向越来越小；不同坡度和流量条件下产沙量在开始的1-2min内便达到最大值，随着时间的推移逐渐减少。（2）建立了试验条件下坡面径流产沙的计算模型根据两坡段径流冲刷试验和REE示踪的结果，运用灰色关联和多元回归分析方法，分析了各坡段产沙量和水蚀因子之间的关系，结果表明：就单个因子对产沙量的影响而言，水流功率对产沙量影响最大；对多个因子组合对产沙量的影响时发现，流量和坡度组合对产沙量影响最大，据此建立了坡面径流侵蚀产沙量与坡度和放水流量的幂函数关系模型（W₁=aS^bQ^c，a，b，c为系数），这为分坡段侵蚀产沙计算提供工具。（3）建立了坡面不同空间部位径流含沙量与主要水动力参数的相关关系根据两坡段径流冲刷试验和REE示踪的结果，对不同坡段径流含沙量时空变化规律的分析结果表明：各坡段的径流含沙量随时间的增加呈下降的趋势，沿程径流含沙量逐渐增加。通过对不同坡段径流含沙量与佛汝德数和相对重力作用（aω_s/V）的分析，建立了各坡段坡面径流含沙量与佛汝德数和相对重力作用的幂函数关系式（S_w=K（aω_s/V）^a（V²/gR）^b,K，a，b为系数）。（4）揭示了土壤剥蚀率随水流含沙量变化的特征根据两坡段径流冲刷试验和REE示踪的结果可以看出，同一坡度和流量条件下，各坡段土壤剥蚀率随水流含沙量线性增加，不同坡度和流量条件下，各坡段土壤剥蚀率与水流含沙量呈幂函数关系（D_r=αS_w^β，α、β为系数）。（5）揭示了土壤剥蚀率随水蚀动力和水流输沙能力非线性变化的特征根据两坡段径流冲刷试验和REE示踪的结果，通过对不同坡度、不同流量的土壤剥蚀率D_r与有效剪切力（τ-τ_c）和输沙率和挟沙力比值（qS_w/T_c）之间关系的分析，发现当坡度为小手21°时，土壤剥蚀率Dr与有效剪切力和输沙率和挟沙力比值之间线性相关显著；而当坡度大于21°时，土壤剥蚀率与有效剪切力和输沙率和挟沙力比值之间存在幂函数关系(D_r=0.011（τ-τ_c）⁰.161|1-qS_w/T_c|^-11.02，R²=0．752)，从以上分析可知，在试验坡度范围内，坡度为21°是侵蚀产沙的临界坡度。（6）建立了计算土壤剥蚀率的经验模型根据一个坡段径流冲刷试验结果表明，土壤剥蚀率受水流剪切力、水流功率、单位水流功率和单宽能耗因素的影响，运用灰色关联方法对土壤剥蚀率与水蚀因子关系进行了分析，分析结果表明：在坡度相同的条件下，土壤剥蚀率随单宽能耗线性增加（D_r=6．95（△E_耗-1．45），R²=0．91）；在流量相同的条件下，水流剪切力与土壤剥蚀率存在幂函数关系(D_r=2．05τ^1.7，R²=0．908)；在不同坡度和流量条件下，土壤剥蚀率与坡度和流量之间呈幂函数关系(D_r=1．264S^0.722Q^1.083，R²=0．695)。通过对土壤剥蚀率与水蚀因子之间关系的逐步回归分析，建立了基于水流功率和坡度的土壤剥蚀率计算方程（D_r=11．22+34．01ω-2．18S，R²=0．977）。更多还原

【Abstract】 Soil erosion on the slope is one of the important contents in water erosion. Its process and development is the core of soil erosion dynamic mechanics, and also is the key for the prevention of soil and water loss and development of physical model for soil erosion prediction. In this paper, runoff scouring on slope-changing flume was adopted to study dispatch, detachment, transportation and sedimentation process on the slope by runoff. Combined with Rare Erath Element （REE） tracing method, grey correlation analysis and statitical method, spatial and tempoal changing patterns of slope erosion dynamic and sedeiment yield process was analyzed, corresponding relation between erosion dynamic parameters and sedeiment yield was stated, followed that relation between soil detachment rate and erosion dynamic parameters and sediment content was revealed, and at last soil detachment rate model was setup. Based on those research, following conclusions can be reached:（1） Expounding the spatial and tempoal changing patterns of slope erosion dynamic and sedeiment yield processUnder the experimental condition, main runoff dynamic paramets changing regularly. Reynold number, runoff shear stress and runoff power decreased along the slope, while Fr and flow velocity increased; runoff power and runoff shear stress increased with time. To sediment yield, soil erosion was most intensive on upper parts, and also was the main source of sediment. From the upper to the bottom, percentage of sediment yield on each section decreased, together with the sediment yield along the depth direction. Analysis of sediment yield under different slope gradient and flow discharge indicated that sediment yield reached its peak value in 1-2 minutes, and decreased gradually with time. （2）Establishing the runoff and sediment yield model on slope under experimental conditionAccording to the runoff scouring data and analysis of REE, combined with grey correlation and multivariate statistical analysis, the relation between sediment yield and hydro-dynamic parameters was analyszed. The results indicated that among all the factors, runoff power contributed most to sediment yield; while amog the combinations of factors, combination of runoff discharge and slope contributd the most to the sediment yield. Based onthis, relation between sediment yield and slope and runoff discharge was set up as W₁ = aS^bQ^c,which provided method for the calculation of sediment yield on each section.（3） Establishing the relation between sediment concentration of different section and main hydrodynamic parameters.According to the runoff scouring experiment and REE tracing data, temporal and spatial patterns of sediment concentrattion on different slope section were analyzed. Result indicated that sediment concentrattion on different slope section decreased with time, which increased along the slope. Based on the analysis of sediment concentrattion on different slope section,froude mumber （V²/gR） and relative gravitational effect （aω_s/V）, power function was set up amongthese factors as S_w = K（aω_s/V）^a（V²/gR）^b.（4） Revealing the changing patterns of soil detachment rate with sediment concentration According to the runoff scouring experiment and REE tracing data, it can be concludedthat under the same slope and runoff discharge, soil detachment rate changed with sediment concentration linearly, while under diferent slope and runoff discharge, power functions,listed as D_r =αS_w^β, was existed between soil detachment rate and sediment concentration.（5） Revealing the non-linear characters of soil detachment with sediment transportationBased on the runoff scouring experiment and REE tracing data, relation among soildetachment rate, effective shear stress （τ-τ_c ）, and the ratio between sediment transportation rate and sediment-carrying capability was analyzed. And the results indicated that linear relation was existed among soil detachment rate, effective shear stress, and the ratio between sediment transportation rate and sediment-carrying capability when slope was less than 21°, while slope was more than 21°, power function was existed among these factors, which waslisted as D_r = 0.011 （τ-τ_c）^0.161|1-qS_w/T_c|^-11.02.It was also can be concluded that critical slope forsediment yield was 21°in this experiment.（6） Establishing the statitical model for soil detachment rate calculationResults of runoff scouring experiment indicated that soil detachment rate was influencedby shear stress, runoff power, unit runoff power and unit runoff energy consumption. Analysisby gray correlation and stepwise regression indicated that linear relation asD_r =6.95（△E_耗-1.45） was existed between soil detachment rate and unit runoff energyconsumption under the same slope condition; power relation as D_r =2.05τ^1.7 was existed between runoff shear stress and soil detachment rate under the same runoff discharge; and power relation as D_r =1.264S^0.722Q^1.083 was existed between runoff shear stress, slope andsoil detachment rate under different slope and runoff discharge.Based on stepwise regression analysis the relation between soil detachment rate and hydrodynamic parameters, equation for soil detachment calculation was determined asD_r = 11.22 + 34.01ω- 2.18S.更多还原