Geomorphological processes due to intermittent sediment movements such as land slides and slope failures

提出了一种描述弱粘性细沙坡面河道化的数学模型。将分析扩展到包括任意形状的斜坡的情况。发现初始通道的间距约为表面片流的弗劳德临界深度的1000倍。文中还提出了一种沟道分岔的数学模型。分析表明，当流量减小时，沟道头变得不稳定，沟道发生分叉。结果与观测结果一致。对渗流侵蚀下河道的形成进行了实验研究。结果表明，控制参数为流量、坡度和渗流层厚度，间距随这些参数的增大而增大。基于多孔介质理论，对地下水位以上毛细带进行了三相液化分析。在假设孔隙流体相对于土骨架的相对加速度较小的情况下，推导了简化的控制方程。当饱和度大于70%左右时，该方法能较好地再现三轴试验结果。数值计算结果表明，当初始饱和度约为60%及以上时，毛细区发生液化。采用入渗分析法分析了考虑融雪的水力梯度。东北地区的概率和道路损坏情况以1公里分辨率的地图显示。这些地图显示了由于某些融雪条件导致的沉积物危害的时空风险分布。研究了全球变暖导致的异常天气条件对大坝水库过量泥沙灾害的影响。研究结果表明，泥沙危害概率模型能够较好地预测大坝库区宏观尺度的泥沙蓄积。

A mathematical model is proposed to describe the channelization on slopes composed of weakly cohesive fine sediment. The analysis is extended to include the case of slopes with arbitrary shapes. The spacing of incipient channels is found to be on the order of 1000 times the Froude critical depth of surface sheet flow. A mathematical model of channel bifurcation is also proposed. The analysis reveals that channel heads become unstable and channel bifurcation takes place when the discharge decreases. The results are found to be consistent with observations. The formation of channels due to seepage erosion is studied experimentally. It is found that governing parameters are discharge, slope and seepage layer thickness and that the spacing increases with those parameters.A liquefaction analysis for capillary zone above ground water level is developed based on porous media theory with three phases. Simplified governing equations are derived with the assumption that the relative acceleration of pore fluid with respect to soil skeleton is small. The proposed method can reproduce the tri-axial test results well when the degree of saturation is larger than about 70%. The numerical results show that liquefaction occurred in the capillary zone when the initial saturation degree is about 60% and over.Hydraulic gradient was analyzed by infiltration analysis with consideration of snowmelt. The probability and the road damage in the Tohoku region are shown in maps with 1 km resolutions. These maps show spatial-temporal risk distributions of sediment hazard due to some snowmelt conditions. We also focus on the influence of dam reservoirs to cause excessive sediment disasters due to anomalous weather conditions by global warming. Results of this study conform that the sediment hazard probability model performs well to predict macro scale sediment storage in dam reservoirs.