Bed form and bed load variation of each grain size due to discharge change in mountain rivers with sand gravel mixture

通过对山区河流河床的调查和室内试验，探讨了山区河流砂砾石床阶塘形态及各粒径输沙量。主要研究结果如下：1）山区河流中的输沙量通常随时间而波动，这是由于在纵向上离散形成的砾石浓度的形成和破坏，从而形成阶梯状或横向肢状床; 2）通过修正均匀沙床推移质方程中各粒径的牵引力和临界牵引力，提出了砂砾混合物中各粒径的平均河床变形方程; 3）山区河流中的台阶-池结构随着台阶的组合和分割而改变，但不会被洪水完全破坏。

Step-pool morphology and sediment discharge of each grain size in mountain rivers with sand-gravel bed are disussed by surveying a mountain river bed and carring out indoor experiments. The main results obtained in this study are as follows :1) Sediment discharge in mountain rivers usually fluctuates with time due to the formation and destruction of gravel concentration formed discretely in the longitudinal flow direction which results in stair-like or transverse limb bed.2) An equation for average bed lood for each grain size in a sand-gravel mixture is proposed by modifying the tractive force and critical tractive force on each grain size in a bed load equation for a uniform sand bed.3) The step-pool structure in mountain rivers is changed with the combination and division of the steps, but it is not completely destroyed by the floods.