Seepage through the core and the foundation of embankment dam is one of the most important monitoring factors in terms of safety control. Therefore, many zoned rockfill dams constructed recently in Japan are provided with improved seepage collection system and seepage observation holes. Improved seepage collection system measures the volume of seepage through the core and the foundation of rockfill dam by dividing it into several flows by seepage collecting walls installed just downstream side of the core. Seepage observation holes, installed from inspection galleries, monitor the pressure and the volume of seepage into the holes. Although the data obtained from these devices provide important information on permeability of the core and the foundation, quantitative analysis has not been conducted so far. In this study, a practical analysis method based on potential theory was proposed; it was found that the concept of permeability efficiency coefficient, which was derived from this analysis method, is useful for analyzing the data obtained from the seepage collection system and seepage observation holes. Since the permeability efficiency coefficient is determined by the permeability coefficient and the shape of the foundation, permeability of foundation can be monitored by calculating the permeability efficiency coefficient from the observation data. In addition, a case history where imperviousness of foundation was improved by grouting while monitoring the data obtained from the devices, is also shown in this paper. These results show that the proposed analysis method and measurement by the improved seepage collection system and seepage observation holes are reliable means for monitoring permeability of foundation.
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