【作者】 吴冰；

【导师】 邵明安； 朱元骏；

【作者基本信息】 西北农林科技大学 ， 环境科学， 2012， 硕士

【摘要】 量化土壤中砾石对坡面径流和入渗的影响有助于深入理解坡面水土过程、促进水土资源的保护和利用。本文在室内模拟降雨条件下研究了不同砾石含量、坡度及降雨强度下的坡面产流、径流泥沙及入渗过程，得出以下结论：（1）模拟高强度降雨条件下（120mm/h），坡面流流速和弗汝德数随着坡度增加而增大，坡面水深和阻力系数呈减小的趋势。与均质土壤相比，含砾石土壤的雷诺数及阻力系数增大。坡度为5°时，随着砾石质量分数的增加，坡面流由缓流转变为急流；坡度为10°和15°时，5中砾石质量分数的土壤的坡面流均为急流。坡面产流前入渗量随着砾石质量分数的增加呈减小的趋势，入渗减少量与砾石体积含量呈显著线性正相关。（2）在模拟降雨条件下对5种土壤（砾石质量分数分别为0、10%、20%、30%、40%）的坡面流速及产流产沙过程进行研究，以期深入了解含砾石土壤的水土流失过程。研究结果表明，含砾石土壤的坡面流速和径流量大于不含砾石的土壤；在降雨初期0～10min内，含砾石土壤的产沙量随时间呈显著增加趋势，峰值出现在10min左右，随后产沙量逐渐降低；降雨后期30～60min内，含砾石土壤的产沙量又呈增加趋势，尤其是砾石含量为30%和40%的土壤产沙量显著增加，且随时间有一定波动。试验中，5种土壤的总产沙量与砾石含量正相关，径流含沙率与产沙量则呈显著线性正相关。（3）通过室内模拟降雨试验，分析了3个坡度下含砾石土壤中的径流和产沙过程，研究结果表明：不同砾石含量的土壤在不同坡度下的产流在0-20min内有明显增加的趋势，之后径流趋于平稳。随着砾石含量的增加，坡度对径流的影响减弱。坡面产沙高峰期出现在0-20min内，且高峰期产沙量占总产沙量比例相对较大；当坡度为15°时，砾石含量（质量含量百分比）为20%、30%和40%的土壤在30min后产沙量又增加，与其他坡度相比，土壤总产沙量也明显增加。实验中坡度是决定土壤产沙量的主要因素。（4）通过室内模拟降雨研究降雨强度对含砾石土壤产沙及入渗的影响。结果明：整个降雨过程中,60mm/h的降雨强度下，产沙率变化相对平稳，在90mm/h和120mm/h的降雨强度下，土壤产沙率的变化均因为有细沟而产生波动，120mm/h的降雨强度下，细沟出现的时间较90mm/h的降雨强度提前了5～20min；降雨强度的增加导致土壤总产沙量也显著增加，当降雨强度从90mm/h增加到120mm/h时，总产沙量的增加量是降雨强度从60mm/h增加到90mm/h时总产沙量增加量的0.83～2.82倍；随着降雨强度的增加，土壤的入渗率有减少的趋势。Kostiakov模型和Horton模型均可以很好模拟3种降雨强度下含砾石土壤的入渗过程，而在60mm/h的降雨强度下，Horton模型优于Kostiakov模型，在90mm/h和120mm/h的降雨强度下，Kostiakov模型优于Horton模型。（5）在65mm/h降雨强度和5种坡度（5°、10°、15°、20°、25°）下，土壤的产流时间随着砾石覆盖度的增加呈增加的趋势，也就是说砾石覆盖度越大越能延缓坡面产流，产流时间与砾石覆盖度呈线性正相关关系。砾石覆盖度对土壤的产流产沙有一定的影响，尤其对泥沙量的影响较为显著，在坡度一定的情况下，随着砾石覆盖度的增加，土壤的泥沙量呈增加的趋势，值得注意的是，当砾石覆盖度从20%增加到50%，泥沙量显著增加，与覆盖度为0的土壤相比增加了10到20倍；在坡度为5°、10°、15°时，土壤的径流量随着砾石覆盖度的增加呈增加的趋势，而在坡度为20°、25°时，土壤的径流量随砾石覆盖度的增加呈先减少后增加的趋势，说明坡度对土壤径流量有重要的影响。更多还原

【Abstract】 Gravel is different from soil particles in density, size, and water permeability, surface andchemical structure, this will affect and change the structure and the physical properties for soiland the exsitace of rock fragments in soil lead to differences of the movement of watercompared to that in homogeneous soil, In this paper, study on runoff and infiltration in theslope as affected by gravels, the main conclusions were drawn as follows:(1) In this study, simulated rainfall experiments were carried out in order to investigate soilhydraulic parameters and infiltration for soil with five gravel contents (massive fractions as0,10%,20%,30%and40%) under three slope gradients (5°,10°and15°) and rainfall intensity of120mm/h. The results showed that Fronde number and overland flow velocity for theexperimental soils increased and runoff depths and Darcy-weisbach friction coefficientsdecreased with increasing slope gradient. The Reynolds number and the Darcy-weisbachfriction coefficients for the soils containing gravels were larger than that of the soil withoutgravels. The runoff type of the soils belonged to laminar flow and then the runoffs changed fromslow-flow into torrent flow with the increase of gravel content on the slope of5°. The overlandflows of the soils on the slopes of10°and15°were torrent flows. The infiltration amount priorto runoff generation decreased with the increase of gravel content. Reduction of infiltration wassignificantly linearly related to gravel content. the infiltration after runoff containing gravel of10%is larger than that of the soil containing gravels of0,20%,30%and40%. Both of Kostiakovinfiltration model and Philip equation could describe the rainfall infiltration process well．(2) In this study, the flow velocity and the processes of runoff and sediment generationsalong the slopes for five soils (gravel mass contents were0,10%,20%,30%, and40%,respectively) were investigated under rainfall simulation experiments in order to improve theunderstanding of soil and water loss process in the soil containing gravels. The resultsindicated that the flow velocity for soil containing gravels was larger than the soil withoutgravels. During the initial0-10min of the rainfall, sediment yields in the soils with gravelsincreased sharply with time and the peak period of sediment generations appeared around10min. Then, sediment yields decreased gradually. At the later stage of the rainfall (30-60min), the sediment yields for the soils with gravels increased again especially for the soils with30%and40%gravel contents their sediment yields enhanced significantly and fluctuated with time.In the experiments, the total sediments yield was positively linked to the gravel content in thesoil and the sediment concentration was positively linearly related to the sediment yield.(3) Investigation on the process of runoff and sediment in stony soil can help tounderstand soil and water process in this kind soil and also provide significant soil parametersfor soil erosion process-modeling. In this study, the processes of runoff and sediment in soilcontaining gravels under three slope gradients were analyzed by simulated rainfallexperiments. The results indicated that the runoffs in stony soil increased obviously during0-20min and then became steady. The effect of gradient on runoff was weakened with theincreasing of gravels in the soils. The peak period of sediment generation appeared between0-20min. The sediment yields generated during this stage accounted for a considerableproportion to the total. When the gradient reached15°, the sediment yields of soils with thegravel contents of20%,30%and40%increased again after30min. And total soil sedimentyields under this gradient increased greatly compared with others. In the experiments, thegradient of the slope dominated the sediment yield.(4) The sediment yield and infiltration are affected by rainfall intensity based onsimulated rainfalls. The results showed that the sediment delivery rate changed smoothlyunder rainfall intensity of60mm/h and the sediment delivery rate fluctuated due to rill duringrainfall, the appearance of rill need more time of5～20minutes under rainfall intensity of90mm/h than that under rainfall intensity of120mm/h, the total sediment yield was increasedobviously with the addition of rainfall intensity, the increased quantity of total sediment yieldfrom60mm/h of the rainfall intensity to90mm/h was0.83～2.82times more than that from90mm/h of the rainfall intensity to120mm/h; with the increasing of the rainfall intensity, theinfiltration rate was decreasing, The rainfall infiltration process in soil containing gravelsunder three rainfall intensities could be well simulated by the experiential infiltration modelof Kostiakov and Horton. Horton model showed better fitting effect of water Infiltrationprocess under rainfall intensity of60mm/h, Kostiakov model showed the fine fitting effectunder the rainfall intensity of90mm/h and120mm/h.(5) The runoff generation time increases with the increase of gravel coverage degreesunder rainfall intensity of65mm/h and the five different slopes, The runoff generation timewas linearly related to gravel coverage degrees; the runoff and sediment yield are affected bygravel coverage degree, the influence of sediment yield is significant, compared to the soilwith the gravel coverage degree of0, the sediment yield significantly increase when thegravel coverage degree increase from20%to50%, the runoff increase with the increase of gravel coverage degree under the slopes of5°、10°and15°, the runoff is less after trend ofincrease under the slopes of20°and25°, the slope has the important influence for the runoff.更多还原