Unified View of the Mechanics of Debris Flows and Sediment Laden Flows

本研究试图统一处理以下主题：流水泥沙混合物的本构关系，泥石流到双推移质水流的含沙量和流速分布，以及计算悬浮流参考浓度的“清水层”。在这项研究中，由Egashira等人提出的本构关系。包括泥沙粒径、颗粒间摩擦角和泥沙比重等物理参数。通过两年的实验和理论研究，研究了泥石流颗粒间摩擦角对泥石流的影响。研究结果表明：刚性床面上的泥石流，颗粒间摩擦角的增大导致水流阻力增大。另一方面，在泥石流的侵蚀床上，泥石流出现了相反的趋势。从实验和理论上研究了泥沙粒度对泥沙-水混合物流动的影响。实验采用了不同大小的沙子，在该地区从泥石流到包括清水较大的水流。将水槽试验得到的数据与数值模拟的流速、含沙量分布进行了比较。计算结果与水槽资料吻合较好。方法利用S的本构关系，并考虑雷诺应力的垂向分布，提出了一种预测悬移流参考浓度和参考水位的方法，该方法在泥沙粒径较小时，参考浓度较小。计算结果与前人的实验数据吻合较好。

This study has attempted a unified treatment of the following themes : the constitutive relationships of flowing water-sediment mixture, the profiles of sediment concentration and flow velocity from debris flows to flows with both bed-load, and "clear" water lagers to calculate the reference concentration of suspended flows. In this study, the constitutive relationships proposed by Egashira et al. include some physical parameters : the sediment size, the interparticle friction angle and specific weight of sediment etc.The effects of interparticle friction angle on debris flows have been investigated experimentally and theoretically for two years. The following results were obtained : in debris flows over rigid beds, an increase of interparticle friction angle causes flow resistance to increase. On the other hand, in debris flows over erodible beds, the inverse tendency appears.The influence of sediment size on flow of sediment-water mixture were investigated experimentally and theoretically. An experiment was employed with different sizes of sand, in the region from debris flows to the flows including a clear-water larger. The data obtained by flume tests were compared with the numerical simulated profiles of velocity, and sediment concentration. The calculated results agreed well with the flume data. The sediment transport rate became small when the sediment size was large, and became large when the sediment size was small for both large or small bed shear stress.Methods to predict the reference concentration and reference level of suspended flows were proposed using Egashira et al.'s constitutive relationships and taking the vertical distribution of the Reynolds' stress into account According to this method, the reference concentration was small when the sediment size was small. The calculated results were fitted with previous experimental data obtained by many researchers.