UNDERGROUND FLOW THROUGH PIPES AND ITS INFLUENCE TO LANDSLIDES

点击翻译按钮获取中文摘要

A two-year observation of the discharge from underground pipes made the following things cclear.First, ten natural pipes were found in a small hollow. Three pipes of the seven pipes, which are located at the downstream end of the hollow, always discharge water. The others drain only during heavy rains. Most of the volume of the direct discharge is covered by the pipe water flow.Second, the pipe water flow can only be seen when the antecedent rain and rainfall intensity is enough.Third, the patterns of the pipe flow rate correstpond well to rainfall patterns.Forth, the discharge rates from the pipes have the upper limits. The limits may be controlled by the dimensions of the pipes.Fifth, two pipes were dug out. They last only 50 cm long and lead to a layr if gravel. This means that the flow that comes out of these pipes should in this case not be called pipe flow but rather gravel layr flow.Sixth, the outflow rates from pipes are will explained with a tank model.These facts could possibly explain the coincidence between the peak time of rainfalls and the time of the occurrence of debris flows and/or landslides that have not been able to be explained by theories developed assuming homogeneous soil layrs. Smooth outflow through pipes, however, does not explain the occrrence of debris flow. Pipe collapse can happened and yhis was observed once during the observation period, these collapses increase the hydraulic pressure and may trigger landslides.