引黄灌区浑水管道输水临界不淤流速分析与计算

为了解决引黄灌区浑水管道输水灌溉工程中泥沙淤堵问题,合理确定临界不淤流速,用试验沙样和清水配制了6组不同含沙量的浑水水样,在4种规格管径的管道中进行了浑水管道输水临界不淤流速试验．分析了浑水含沙量、输水管径、泥沙密度和颗粒粒径对临界不淤流速的影响．结果表明:当管径和泥沙密度不变时,临界不淤流速随含沙量的增大而增大;当含沙量和泥沙密度不变时,临界不淤流速随管径的增大而增大;泥沙密度和粒径对临界不淤流速影响也很明显,特别是泥沙颗粒的上限粒径(d90或d95),一般最先沉降到管底的是粒径比较大的泥沙颗粒．同时,基于泥沙悬浮效率系数和悬浮泥沙能量耗损的角度,建立了临界不淤流速计算公式;利用试验数据,确定了泥沙悬浮效率系数计算方法;经试验并比较了临界不淤流速的实测值与计算值,两者之间的最大误差为2958％．

Analysis and determination of critical non-silting velocity of muddy water conveyance pipelines in Yellow River irrigation districts

Sediment problem is the key factor that restricts the development of pipeline water conve yance irrigation engineering in Yellow River irrigation districts. In order to solve this problem, it is necessary to reasonably determine a critical non silting velocity of water conveyance pipelines in Yellow River irrigation districts. In doing so, a series of experiments on muddy water transport in pipelines were carried out by using four kinds of size of pipe diameter and six groups of sediment concentrations which were mixtures of water and various sand contents. Then influences of sand density, particle size, sediment concentration and pipe diameter on the critical non silting velocity were analyzed. The results showed that as the pipe diameter and sand density remain unchanged, the critical non silting velocity is increased with increasing sediment concentration. If the sediment concentration and sand density are kept constant, then the critical velocity is increased with increasing pipe diameter. The influence of sand density and particle size on the critical non silting velocity is also very obvious, especially for the sand particles with a size close to the upper limit of sand particle size (d90 or d95), which often deposit in the bottom of a pipe initially. Further, an empirical formula for calculating the critical non silting velocity was established based on the sediment suspension efficiency coefficient and the suspended se diment energy dissipation principal. The sediment suspension efficiency coefficient has been determined by the experimental data. It was confirmed that the maximum error is 2.958% between the predicted critical velocity and experimental one.