挟沙水流的冲刷率及河床惯性的研究  

A study on channel scour rate of sediment laden flow and river bed inertia

作　　者：王兆印 徐永年[2] 苏晓波[2] 

机构地区：[1]北京国际泥沙研究培训中心 [2]中国水利水电科学研究院

出　　处：《泥沙研究》1998年第2期1-9,共9页Journal of Sediment Research

基　　金：国家自然科学基金

摘　　要：在清水水流河床冲刷率的实验研究基础上，本文进一步研究了挟沙水流来沙率对冲刷率的影响。结果说明挟沙水流的冲刷率随来沙率与水流输沙力欠饱和度之比以负指数律降低。当来水挟沙率与水流饱和输沙率相等时，冲刷率降到０。河床惯性是河床在非恒定流中一种重要的动力学性质。利用河床惯性与冲刷率的关系测量了各种沙样的河床惯性值。发现河床惯性随床沙颗粒分选系数增大而增大，分选系数很大时趋近于极限值５０ｔ／ｍ２。利用河床惯性和河床变形方程得出了冲刷过程中水流输沙率沿程和随时间的变化规律，结果说明水流输沙率欠饱和度向下游以负指数律下降，这与冲刷率随实际水流挟沙率与欠饱和度之比以指数率下降的规律有相同意义。河床惯性愈大，实际水流输沙率增长得愈慢。河床惯性与干容重及摩阻流速之比构成的无因次数ＡＲ代表河床变形和水流实际挟沙量对水流挟沙力变化的响应程度。ＡＲ值愈大，河床演变对变化的水流愈适应。对天然河流最大河床冲刷率采用实验得出的冲刷率公式和河床惯性进行了计算，用实测结果验证了冲刷率公式。The rate of channel bed scour in sediment laden flows are experimentally studied. The results show that the scour rate is high if the flow carries no sediment and reduces following increase in sediment concentration and the unsaturation of the sediment carrying capacity of the flow. If the sediment load is equal to the flow capacity, the average scour rate of the flow is zero. River bed intertia is an important nature of alluvial river bed and is closely related to the bed scour rate in unsteady flows. The inertia of the channel bed composed of various bed materials are calculated by using the relationship between the intertia and the scour rate. The bigger the sorting coefficeint of the bed material, the higher the river bed intertia. The river bed inertia reaches its maximum value of 50 t/m 2 if the sorting coefficient is over 15. The concept of river bed intertia is used to solve the river deformation equation and concludes that the unsaturation of sediment carrying capacity reduces exponentially with time and downstream distance. The bigger the bed inertia, the slower the bed deformation and the lower the increase in transport rate. A dimensionless number composed of the bed inertia, the specific weight and the shear velocity indicate the conformity of the bed deformation and sediment transport rate with the unsteady flow. The scour rate formula is verified with measured river bed scour during flood. The maximum scoured depth is calculated with the scour rate formula.

关 键 词：河床变形 水流输沙 挟沙水流 床沙 摩阻流速 水流挟沙力 非恒定流 冲刷率 涉水 河床冲刷 

分 类 号：TV142[水利工程—水力学及河流动力学] U442.3[建筑科学—桥梁与隧道工程]