1降雨に対して2回の流量増加があるパイプ流の流出機構

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In the pipes developed in the pyroclastic deposits with andosol top layer, an increase in the discharge was obserbed twice during a rainfall event. In this paper, this phenomena is discussed considering the variations in hydraulic head among the slope layers and solute concentration. Especially, in the heavy storm, the first increase might be due to piston flow of the pre-event water in the unsaturated capillary zone at the lower slope, after that, the source of pistonflow changed into the deeper layer, the second increase should be flowage of event-water furnished from upper slope. The process of piston flow were presumed due to descent of the unsaturated capillary water by wetting front reaching and increase of the entrapped air pressure. Piston flow well responded to the rainfall intensity but was small in volume. The second increase occurred 7-35 hours after the peak intensity of rainfall, occasionally accompanying a gurgling sound. Then, the saturated zone in the upper slope expanded to the periphery of the pipe system. The gurgle was considered to be due to the air entrained within the unsaturated zone. After the gurgle, a spurt of muddy water with gravel from some pipes was recognized. Although, up to the present the pipeflow has been considered to be closely related to runoff and to be a trigger of the slope failure contemporaneous with heavy rain, this later spurt of the pipeflow suggests that it would be a contributor to the hydrogeomorphological phenomenon after the finale of rainfall, as well.
日本地形学連合の論文
2002-10-25

1降雨に対して2回の流量増加があるパイプ流の流出機構

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