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

(1)床质型质量运动浓度和速度分布图。将床质型质量运动视为两层流动。针对地下高浓度，分别在流动方向和垂直方向建立了力平衡方程。由这些方程推导出平均浓度和速度分布。利用经验方程对下垫层深度进行估计。在上层，根据气流方向上的力平衡推导出流速分布方程。通过对各层的速度分布进行积分，得到了整个流场的速度分布。根据这些结果，得到了流速系数和流动浓度方程。通过与水槽数据的比较，验证了这些方程的有效性。(2)输沙速率。利用上述方程，推导出输沙速率方程。该方程与陡坡河道的泥石流方程吻合，与极缓坡河道的常规河床荷载函数相似。这些事实表明，新方程适用于从河床到泥石流的广泛范围。(3)水淹沉积模拟。提出了利用水流阻力方程和输沙速率方程进行模拟的方法。将该方法应用于云仙火山水水河泥石流危险区的估算。在模拟中，利用神经网络径流分析得到的水流曲线计算出了上边界条件。模拟中还采用了新的输沙速率方程。模拟结果与现场数据吻合较好。通过这种方法，可以对给定降雨的危害区域进行估计。

(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.