STUDY ON MECHANISM OF FLOW AND DEPOSITION OF DEBRIS-MUD FLOW

(1)推移质运动的浓度和速度分布，将推移质运动视为两层流。对于下层浓度较高的情况，建立了流动及其垂直方向的力平衡方程。由这些方程得到了平均浓度和速度分布。下垫层深度用经验公式估算。在上层，根据流动方向的力平衡，推导出速度分布方程。通过积分各层的速度分布，给出了整个水流的速度分布。在此基础上，得到了流速系数和浓度的关系式。通过与水槽资料的对比，验证了这些公式的正确性。(2)输沙速率。利用上述方程，推导出输沙速率方程。该方程与陡峭河道泥石流方程吻合，与缓坡河道传统推移质推移质函数相似。提出了基于水流阻力方程和泥沙输沙率方程的洪水泥沙模拟方法。将这种新方法应用于云顶火山的水石河泥石流危险区的估算。在模拟中，利用神经网络的径流分析得到的过程线来计算上边界条件。模拟中还采用了新的输沙率方程。模拟结果与现场数据吻合较好。通过这种方法，可以估计给定降雨量的危险区域。

(1) Profiles of concentration and velocity of mass movement of bed load type.The mass movement of bed load type was treated as a two layr flow. To the under layr high concentration, equations of force balance were set in flow and its vertical direction. The averaged concentration and velocity distribution were derived from these equations. The depth of the under layr was estimated by using empirical equation. In the upper layr, equation of velocity distribution was derived from the force balance in flow direction. The velocity profile of whole flow was given by integrating velocity distribution of each layr. From these results, equations of velocity coefficient and concentration of flow were obtained. The validity of these equations were examined by comparing with flume data.(2) Sediment transport rate.By using equations mentioned above, equation for sediment transport rate was derived. This new equation coincides with that of debris flow on steep channel, and is similar with conventional bed load function on very mild slope channel. These facts suggest that the new equation is applicable in the wide range from bed load to debris flow.(3) Simulation of flooding and deposition.Simulation method by using equations of flow resistance and sediment transport rate was proposed. This new method was applied to the Mizunashi River in Unzen Volcano to estimate the hazard area due to debris flow. In the simulation, the upper boundary conditions were calculated from the hydrograph obtained by using runoff analysis of neural network. New equations of sediment transport rate was also used in the simulation. The simulated results show good agreement with the field data. By this method, estimation of hazard area for a given rainfall is possible.