【作者】 杨具瑞；

【导师】 方铎；

【作者基本信息】 四川大学 ， 水力学及河流动力学， 2003， 博士

【摘要】 本研究采用力学方法，在对土壤泥沙受力分析的基础上，结合实内试验和野外观测资料的分析，对三种主要土壤侵蚀类型的侵蚀产沙过程和产沙特性进行了一些研究探索，探讨了非线性科学的尖点突变理论和方法在小流域侵蚀产沙过程研究中的应用，全文主要包括以下四个部分内容： 1．坡面流侵蚀产沙 本部分从水动力学角度探讨了坡面流条件下坡面泥沙起动、输移的基本特性，对坡面土壤侵蚀研究中的主要问题如细沟侵蚀的临界坡度、临界坡长、稳定细沟宽度、坡面面蚀及细沟侵蚀等进行了探讨。 根据坡面流流动特性和坡面泥沙起动特性，在坡面泥沙起动研究中引入粘着力，并考虑泥沙颗粒暴露度的影响，通过坡面单颗粒泥沙受力分析，采用泥沙颗粒滚动模式建立了坡面流泥沙起动公式。借助梅叶-彼德泥沙输移方程的形式，根据坡面流输沙特性和本文推导的坡面流泥沙起动公式，将泥沙起动粒径取为泥沙最容易起动的粒径，得到坡面面蚀的泥沙输移公式。在形成稳定细沟的坡面泥沙侵蚀计算中，将泥沙起动粒径取为坡面泥沙的代表粒径，得到坡面细沟侵蚀的泥沙输移公式。以坡面坡长为L处的坡面水流流速与该处泥沙起动流速相等时的坡长为临界坡长，应用坡面流泥沙起动流速公式得到细沟侵蚀临界坡长的计算公式。对于形成稳定细沟的坡面，在坡长和坡度一定时，假设细沟内水流流速与细沟泥沙起动流速相等，得到细沟侵蚀中细沟稳定宽度的计算公式。通过细沟稳定宽度计算分析得到，细沟稳定宽度随着坡度增加而出现～临界坡度，使细沟稳定宽度为最大，这一临界坡四川大学博士学位论文小流域侵蚀产沙特性研究度即为坡面细沟侵蚀的临界坡度。对于中值粒径为o.O185mm的黄土坡面，临界坡度为3990。同时，在计算分析中发现，存在一最大粒径仓O198mm，当坡面泥沙颗粒粒径大于这一值时，坡面不发生细沟侵蚀，对应的最大临界坡度为50.40。对以上的计算公式，用试验资料和野外观测资料进行了验证，吻合情况较好。 2.风力侵蚀产沙 本部分从动力学角度探讨了平面风沙、坡面风沙的泥沙起动、输移的基本特性。将水流条件下河床泥沙起动的暴露度概念引入到风沙起动的研究中，定义风沙暴露度的概念，并对风沙暴露度的统计规律进行了分析。根据风沙暴露度的概念，采用滚动模式分别建立了坡坦地面风沙和坡面风沙颗粒起动的风速公式，得到了在风力、风向、坡面坡度和风沙位置一定的情况下风沙起动方向的计算公式。对坡面风沙在相同风向不同坡度条件下和相同坡度不同风向条件下风沙的起动风速进行了分析。借助河村风沙输移公式的形式，根据本文推导的风沙起动公式，建立了风沙输移计算公式。对以上公式用试验资料和野外观测资料进行了验证，吻合情况较好。 3.冻融风化侵蚀产沙 本部分研究以砒砂岩区西召沟小流域为例，通过典型支沟沟道各变量和冻融风化侵蚀量测量结果的分析，探讨了砒砂岩区冻融风化侵蚀特性，建立了冻融风化侵蚀量和崩塌侵蚀量的计算公式。 通过西召沟小流域冻融风化侵蚀实测资料，分析了冻融风化侵蚀与沟道各变量之间的关系。确定了该流域相同种类支沟上、中、下游的冻融风化坡面侵蚀模数、单位沟沿线沟角线长度和的侵蚀量值，不同种类支沟冻融风化坡面侵蚀模数及单位长度沟沿线沟角线长度和的侵蚀量的比例关系，及上、中、下游冻融风化侵蚀侵蚀量的比例关系。据此建立了小流域单位长度沟沿线沟角线冻融风化侵蚀量比例模型和冻融风化侵蚀模数比例模型。根据西召沟小流域上游20条沟谷的资料，利用两种模型对该流域的冻融风化侵蚀量进行了模拟计算，计算结果分别为23757.9t和29165，lt，相差18.5%。从实测的角度定量地确定了上、中、下游冻融风化侵蚀量占支沟总侵蚀量的百分比，上游占总侵蚀量的76.1%，中游占17.5%，下游占6.4%，从而得到砒砂岩区冻融风化侵蚀主要发生在沟头的重要结论。根据测量资料的分析，.通过7年四川大学博士学位论文摘要的沙棘种植栽培，支沟上、中、下游的坡面冻融风化侵蚀模数平均从11748t/k衬降为3535t/km2，降低69.9%。单位长度沟沿线沟角线和的冻融风化侵蚀量平均从0.0974 m3zm降为o.oo4m3zm，降低95.9%。采用Gzs技术对西召沟小流域风化沟道沟沿线长度进行测量，通过崩塌侵蚀机理的分析，得到崩塌侵蚀量的计算公式，计算得到的崩塌侵蚀量为8386.7t。 4.尖点突变理论在小流域侵蚀产沙过程研究中的应用 应用突变理论，通过对泥沙起动受力分析，将水流参数。作为泥沙起动突变模型的状态变量，沙粒雷诺数Re一。·’和无量纲参数md.，/d。作为泥沙起动突变模型的控制变量。通过坐标变换和拓扑变换，得到非均匀沙起动的尖点突变模式。从非均匀沙受力分析出发，将非均匀沙起动所受到的附加作用力分为两部分，一部分为泥沙粗细颗粒之间相互作用产生的附加作用力，假定该附加作用力与混合沙的平均抗剪力成正比;另一部分为床面糙度对近底水流结构影响的附加作用力，假定该附加作用力与均匀床沙条件下的底部流速平方成正?更多还原

【Abstract】 Based on the analysis of forces acting on the sediment, and the data of both laboratory and field observation, the processes and features of sediment yield for three main types of soil erosion have been studied and explored. The applications of the theory and method of the cusp-catastrophe of nonlinear science for studying the processes of soil erosion in small watersheds have been discussed. The full text includes four parts are as follows:I The processes of erosion and sediment yield from the overland flowIn this part, the incipient motion characteristic and transport character of sediment on hillslope sediment have been studied from the angle of hydrodynamics. Several main problems such as the critical slope gradient, critical slope length, the stable width of rills, the rill erosion on hillslope, interrill erosion of soil erosion and so on in the research of soil erosion on hillslope have also been analyzed and studied.According to the character of overland flow and the incipient motion of the fine particle of sediments, the visous force has been taken into account for the studying of binding incipient motion of sediment on hillslope, in addition, the effects of exposure degree of sediment particle has been taken into account. By using the method of analysis of forces acting on a single particle of sediment on the hillslope, an equation to calculate the threshold velocity of the sediment on thehillslope is established by using the rolling mode for sediment particle resting on hillslopes. The sediment transport equation for rill erosion on the rillslope is also built by using the incipient velocity equation of overland flow and Meyer-Peter equation form for sediment transport rate, as well as taking the easiest incipient motion diameter of the sediment as the incipient motion diameter. In the calculating of soil erosion on hillslope for stable rill, the dso is taken as the representation diameter of sediment, the equation of sediment transport for rill erosion on hillslope has been obtained. The equation of critical length of rill erosion is produced by the overland flow velocity and incipient velocity equation of slope land sediment. The condition of form rill stable width is the rill flow velocity equal to the threshold velocity of the rill sediment, and the rill stable width equation is produced by the incipient velocity equation of rill sediments. Computational results show that the rill stable width is a function of slope gradient, and it has a critical slope gradient when the rill width increase to maximal value. The critical slope gradient is same as the critical slope gradient of rill erosion. The critical slope gradient has a critical diameter. It is 39.9 degree when the sediment diameter is 0.0185mm. The biggest critical slope gradient is 50.4 degree, and the critical diameter is 0.0198mm. The equations are tested by experiment data, and it shows that the calculated results agree wells with the experiments data.II The soil erosion and sediment yield from wind foerceIn this part, the incipient motion characteristic and transport character of wind sediment have been studied in dynamic method. The exposure degree conception that was used in the water flow was applied for the blown sand initiation, and the exposure degree was analyzed by a statistical method. The threshold wind velocity equation of the non-uniform sediment on plant land and slope land were established, and it was tested by the wind tunnel experiment data. The threshold wind velocity of different slope angle in same wind direction and same slope angle in different wind direction have been analyzed. An equation calculated wind direction was built. The erosion rate equation also is built by using the incipient velocity equation andHecun equation form. The equations are tested by experiment data, and it shows that the calculated results agree wells with the experiments data.Ill The erosion and sediment yield process from freeze-thaw and weatheringBased on the metrical data of freeze-thaw and weathering erosion o更多还原