董志塬沟头溯源侵蚀过程及水力学特征野外试验研究

发布时间：2018-06-05 00:05

本文选题：董志塬 + 沟头　；参考：《西北农林科技大学》2017年硕士论文

【摘要】：董志塬塬面广阔平坦,具有极其宝贵的土地资源及农业生产条件。然而长期严重的沟头溯源侵蚀,使塬面面积不断蚕食萎缩,甚至面临损失殆尽的威胁,已成为当地生态建设与经济社会可持续发展的严重隐患。开展董志塬沟头溯源侵蚀过程及水力学特征研究可以深入揭示溯源侵蚀过程机理,深刻认识塬面侵蚀萎缩演变及塬区强烈侵蚀产沙规律,促进沟蚀过程研究进一步发展,为沟蚀过程模型研究奠定重要基础,并为控制董志塬等黄土塬区沟头溯源侵蚀,阻滞塬面侵蚀萎缩及塬区侵蚀产沙,实现董志塬等黄土塬区土地资源有效管理及水土流失科学治理提供重要科学依据。本论文在概化修建的黄土塬塬面模型及沟头模型小区(投影面积皆为5.0×1.5 m~2)上,采用野外定雨强模拟降雨+放水冲刷试验方法,对2个塬面坡度(3°和6°),2个沟坡高度(0 m和1.5 m,沟坡坡度90°),1个固定雨强(2.0 mm/min),4个放水流量(100L/min、200 L/min、300 L/min、400 L/min),各流量连续4场次放水试验条件下的董志塬沟头溯源侵蚀过程及水力学特征进行了研究,分析研究了董志塬土壤物理性质、沟头溯源侵蚀过程、沟头溯源侵蚀水流水力学特征及沟头溯源侵蚀过程动力学机理。主要研究结果如下:(1)不同深度(0~150 cm)土壤容重介于1.23~1.30 g/cm~3之间,平均值为1.26 g/cm3,随土壤深度增加,土壤容重加大;不同深度土壤含水量为10.54%~13.18%,平均值为11.77%,随土壤深度增加,土壤含水量呈先增加后减小的变化;土壤粘聚力和内摩擦角分别为14.92 kPa和13.22°,二者均随土壤含水量增加而减小,土壤含水量达到10%、15%和20%时,粘聚力较含水量为6.31%时(16.39 kPa)分别减小3.05%、6.83%和26.11%,内摩擦角较含水量为6.31%时(15°)分别减小3.58%、13.48%和40.06%;以土壤剖面0~10 cm为基准(0.29 g/min),10~20 cm、20~50 cm、50~90 cm和90~150 cm土层的土壤崩解速率分别增大253.42%、222.28%、380.40%和481.81%,土层越深,土壤崩解速率越快。(2)在放水流量为100~400 L/min,沟坡高度0 m时,塬面坡度3°小区的平均径流率分别为103.71 L/min、270.24 L/min、386.64 L/min、528.46 L/min,平均径流率与放水流量间呈极显著线性相关,6°小区的平均径流率分别为133.10 L/min、154.77 L/min、273.24 L/min和273.11 L/min,平均径流率与放水流量间呈指数相关。沟坡高度为1.5 m时,3°小区平均径流率分别为164.84 L/min、198.27 L/min、211.31 L/min、200.98 L/min,平均径流率与放水流量间呈幂函数相关,6°小区的平均径流率分别为60.12 L/min、122.23L/min、153.07 L/min和240.52 L/min,平均径流率与放水流量间呈极显著线性相关。塬面坡度为3°及6°时,沟坡高度1.5m的平均径流率是0m的158.94%、73.37%、54.65%、38.03%及45.17%、78.98%、56.02%、88.07%;沟坡高度为0m时,塬面坡度3°和6°小区在4个放水流量下的平均产流径流量分别为6222.65l、16214.4l、23198.11l、31707.77l和7986.01l、9286.34l、16394.63l、13182.1l,沟坡高度为1.5m时,对应值分别为9890.58l,11896.38l,12678.8l、12058.73l和3541.14l、7333.53l、9184.10l、13392.54l,沟坡高度为0m时,塬面坡度3°和6°下的平均径流量与放水流量间分别呈线性和幂函数相关,沟坡高度为1.5m时,分别呈幂函数和线性相关,塬面坡度为3°及6°时,沟坡高度1.5m的平均径流量是0m的158.94%、73.37%、54.65%、38.03%和45.17%、78.98%、56.02%和88.07%。(3)沟坡高度为0m和1.5m时,随放水流量增大,塬面坡度3°小区在放水流量100l/min、200l/min、300l/min、400l/min下的平均产沙量分别为99.98kg、368.95kg、586.70kg、806.06kg和353.65kg、463.88kg、654.52kg、849.94kg,产沙量与放水流量间均呈极显著线性相关,产沙量随沟坡高度增加而增加,4个放水流量下,沟坡高度1.5m的产沙量是0m的3.54、1.26、1.12和1.05倍,随沟坡高度增加,沟壁形成抛物线型性侵蚀,产沙量也随之增大;相同条件下,平均含沙量分别为16.88g/l、26.97g/l、29.01g/l、31.60g/l和46.99g/l、65.55g/l、46.12g/l、30.37g/l,沟坡高度为0m时含沙量与放水流量间呈显著的对数函数关系,1.5m时呈抛物线相关,随放水流量增加,沟坡高度对含沙量的影响减缓,4个放水流量下,沟坡高度1.5m的含沙量是0m的2.78、2.43、1.59和0.96倍;试验条件下侵蚀产沙的粘粒、粉粒和砂粒含量平均值为23.02%、68.36%和8.62%,砂粒含量均随放水流量增加而减小,塬面坡度-沟坡高度为3°-0m下粘粒含量随放水流量增加先增后减,粉粒含量先减后增,3°-1.5m下粘粒含量随放水流量增加先减后增,粉粒含量先增后减。(4)放水流量100l/min、200l/min、300l/min、400l/min下,沟坡高度为1.5m,塬面坡度3°和6°小区的平均流速分别为0.75m/s、0.85m/s、0.95m/s、0.99m/s和0.85m/s、1.15m/s、1.06m/s、1.05m/s,塬面坡度为3°时,平均流速与放水流量间呈显著线性相关,而塬面坡度为6°,放水流量在100、200l/min时,平均流速随放水流量的增大而加大,随放水流量继续增加,坡面流速略有下降,但仍大于放水流量为100l/min时的流速。试验条件下雷诺数均大于500,属于紊流流态,弗汝德数均大于1,水流为急流。沟坡高度为1.5m时,塬面坡度3°和6°小区的平均径流剪切力分别为1.71n/m~2、1.92n/m~2、2.75n/m~2和1.95n/m~2、2.71n/m~2、2.76n/m~2、1.37n/m~2,2种坡度下,剪切力与放水流量间分别呈线性函数和对数函数相关;沟坡高度为1.5m时,塬面坡度3°和6°小区的平均径流功率分别为1.27w/m~2、1.63w/m~2、2.61w/m~2、2.84w/m~2和1.05w/m~2、1.19w/m~2、1.56w/m~2、1.56w/m~2,塬面坡度3°小区径流功率与放水流量间呈极显著线性相关,6°小区在放水流量为100~300l/min时,径流功率与放水流量间呈对数函数相关,但放水流量400l/min时,径流功率有所下降;沟坡高度为1.5m时,塬面坡度3°和6°小区的单位径流功率分别为0.039 m/s、0.045 m/s、0.050 m/s、0.052 m/s和0.039 m/s、0.047 m/s、0.052 m/s、0.055 m/s,单位径流功率与放水流量间均呈对数函数相关;次侵蚀产沙量与径流功率间的关系在2种沟坡高度下均为最好,流速和单位径流功率次之,径流剪切力最差,径流功率是与试验条件下沟头溯源侵蚀产沙关系最好的水动力学参数和动力根源。
[Abstract]:Dongzhi tableland has a vast flat surface, and has extremely valuable land resources and agricultural production conditions. However, long and serious gully head retrogressive erosion has made the tableland area continuously shrunk, even faced with the threat of loss, which has become a serious hidden danger to the local ecological construction and the sustainable development of the economy and society. The study of process and hydraulic characteristics can deeply reveal the mechanism of the process of traceability erosion, deeply understand the evolution of the erosion and evolution of the tableland erosion and the law of strong erosion and sediment yield in the tableland, promote the further development of the furrow erosion process, and lay an important foundation for the study of the ditch erosion process model, and control the source erosion of the gully head in the Loess Tableland and other loess tableland areas of Dong Zhi Tableland and block the surface invasion of the tableland. An important scientific basis for effective management of land resources and the scientific management of soil erosion in the loess tableland area of Dongzhi tableland is provided by erosion and erosion and erosion and sediment yield. In this paper, the model of the Loess Tableland of the tableland of the Loess Tableland and the area of the gully head model are 5 * 1.5 m~2 of the projection area, and the field rainfall intensity simulated rainfall + water discharge scour test is used. In the method, 2 slope gradients (3 and 6 degrees), 2 gully slope height (0 m and 1.5 m, groove slope degree 90), 1 fixed rain intensity (2 mm/min), 4 discharge flow (100L/min, 200 L/min, 300 L/min, 400 L/min), the erosion process and hydraulics characteristics of the Dong Zhi gully head under the condition of continuous discharge experiments were studied. The physical properties of the soil in the tableland, the erosion process of gully head traceability, the hydrodynamic characteristics of the water flow and the dynamic mechanism of the erosion process in the gully head are the main results as follows: (1) the soil bulk density at different depths (0~150 cm) is between 1.23~1.30 g/cm~3, the average value is 1.26 g/cm3, and the soil bulk density increases with the depth of soil, and the soil bulk density increases; the soil bulk density increases with the depth of the soil; The soil moisture content is 10.54%~13.18%, the average value is 11.77%, with the increase of soil depth, the soil moisture content increases first and then decreases, the cohesive force and the internal friction angle of soil are 14.92 kPa and 13.22 degrees respectively. The two people all decrease with the increase of soil water content, and the soil water content reaches 10%, 15% and 20%, the cohesive force is 6.31% when the water content is 16.39 K Pa) decreased by 3.05%, 6.83% and 26.11% respectively, and the internal friction angle was 3.58%, 13.48% and 40.06% when the water content was 6.31% (15 degrees), respectively, with the soil profile 0~10 cm (0.29 g/min), 10~20 cm, 20~50 cm, 50~90 cm and 90~150 cm soil increased 253.42%, 222.28%, 380.40% and 481.81%, the deeper the soil layer, the soil disintegration rate. The quicker. (2) when the discharge flow rate is 100~400 L/min and the slope height is 0 m, the average diameter flow rate of the 3 degree plot is 103.71 L/min, 270.24 L/min, 386.64 L/min, 528.46 L/min, respectively. The average diameter flow rate is significantly linear with the discharge flow rate, and the average diameter of the 6 degree plot is 133.10 L/min, 154.77 L/min, 273.24 L/min and 273, respectively. .11 L/min, the average diameter flow rate is exponentially related to the discharge flow rate. When the height of the ditch is 1.5 m, the average diameter of 3 degrees is 164.84 L/min, 198.27 L/min, 211.31 L/min, 200.98 L/min. The average diameter flow rate is related to the power function of the discharge flow, and the average diameter of the 6 degree plot is 60.12 L/min, 122.23L/min, 153.07 L/min and 240., respectively. 52 L/min, the average runoff rate has a very significant linear correlation with the discharge flow rate. When the plateau slope is 3 and 6 degrees, the average diameter of 1.5m is 158.94%, 73.37%, 54.65%, 38.03% and 45.17%, 78.98%, 56.02%, 88.07%, when the slope height is 0m, and the average runoff runoff of the slope 3 degree and 6 degree area under the flood discharge are respectively at 0m. When 6222.65l, 16214.4l, 23198.11l, 31707.77l and 7986.01l, 9286.34l, 16394.63l, 13182.1l, the height of the ditch slope is 1.5m, the corresponding values are 9890.58l and 12678.8l. Function correlation, when the slope height is 1.5m, it is power function and linear correlation. When the slope of the plateau is 3 and 6 degrees, the average runoff of 1.5m is 158.94%, 73.37%, 54.65%, 38.03% and 45.17%, 78.98%, 56.02% and 88.07%. (3) is 0m and 1.5m, which increases with the discharge flow, and the slope of the tableland is 3 degrees in the discharge flow 100l/min, The average sediment yield under 200l/min, 300l/min and 400l/min is 99.98kg, 368.95kg, 586.70kg, 806.06kg and 353.65kg, 463.88kg, 654.52kg, 849.94kg. The sediment yield is significantly linearly correlated with the discharge flow, and the sediment yield increases with the increase of the slope height. Under the 4 discharge flow, the sediment yield of the ditch height 1.5m is 1. In the same condition, the average sediment content is 16.88g/l, 26.97g/l, 29.01g/l, 31.60g/l and 46.99g/l, 65.55g/l, 46.12g/l, 30.37g/l, and there is a significant logarithmic function relationship between the sediment content and the discharge flow when the height of the ditch is 0m, and the 1.5m is parabola when 1.5m is in the same condition. Correlation, with the increase of discharge flow, the effect of slope height on sediment content is slowed down. Under 4 discharge flows, the sediment concentration of 1.5m in the slope height is 2.78,2.43,1.59 and 0.96 times of that of 0m. The average value of the clay grain and sand grain content under the test conditions is 23.02%, 68.36% and 8.62%, and the sand grain content decreases with the increase of the discharge flow rate and the plateau slope. The content of clay particles increased first and then decreased with the increase of the discharge flow rate under the degree of 3 degree -0m. The content of the particles decreased first and then increased with the increase of the discharge flow rate. The content of the particles increased first and then decreased. (4) the discharge flow rate was 100l/min, 200l/min, 300l/min and 400l/min, the slope height was 1.5m, the average velocity of the slope of the tableland and the average velocity of 3 and 6 degrees was 3. When 0.75m/s, 0.85m/s, 0.95m/s, 0.99m/s and 0.85m/s, 1.15m/s, 1.06m/s, 1.05m/s, the slope of the tableland is 3 degrees, the average flow velocity is linearly correlated with the discharge flow, while the slope of the tableland is 6 degrees. When the discharge flow is at 100200l/min, the average flow velocity increases with the increase of the discharge flow, and the flow rate continues to increase and the slope velocity is slightly lower. The flow rate is still larger than the flow rate of 100l/min. The Reynolds number is more than 500 under the test condition, which belongs to the turbulent flow, the Froude number is more than 1, the flow is a jet stream. When the slope height is 1.5m, the average runoff shear force of the 3 and 6 degrees area of the tableland is 1.71n/m~2,1.92n /m~2,2.75n/m~2 and 1.95n/m~2,2.71n/m~2,2.76n/m~2,1.37n/m, respectively. Under the ~2,2 gradient, the shear force and the discharge flow are linear and logarithmic function respectively. When the slope height is 1.5m, the average runoff power of the 3 and 6 degree plots of the tableland is 1.27w/m~2,1.63w/m~2,2.61w/m~2,2.84w/m~2 and 1.05w/m~2,1.19w/m~2,1.56w/m~2,1.56w/m~2 respectively. The runoff power and the discharge flow rate of the plot slope of the tableland are 3 degrees. There is a very significant linear correlation between the flow power and the discharge flow rate of 100~300l/min in the 6 degree area. But the runoff power is logarithmic function, but when the discharge flow is 400l/min, the runoff power is reduced. When the slope height is 1.5m, the unit runoff power of the 3 and 6 degree plots of the tableland is 0.039 m/s, 0.045 m/s, 0.050 m/s, 0.052 m/s and 0., respectively. 039 m/s, 0.047 m/s, 0.052 m/s, 0.055 m/s, both unit runoff power and discharge flow are logarithmic function correlation, and the relationship between sediment yield and runoff power is the best at the height of 2 groove slope, the flow velocity and unit runoff power are the second, the runoff shear stress is the worst, and the runoff power is the relationship between the runoff yield and the sediment yield under the test condition. The best hydrodynamic parameters and power sources.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S157.1

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