Some problems are encountered when old small earth fill dams are reconstructed in Japan. For example, tons of muddy soil is deposited on the bottom of a pond, and it is difficult to remove muddy soil because of the high water content. Furthermore expensive soil for the impermeable core zone has to be prepared because of a lack of suitable soil materials at the dam sites. In this paper, we proposed the creation of the soil for using muddy soil deposited on the bottom of a pond; old dam body's material of fine-grain fraction lack, fly ash and quicklime, and it was found that improved soil was satisfied with standard value of strength and permeability. It was concluded that this method which using waste material could use as soil for impermeable core zone.
Small earth fill dam is artificial pond and the height is under 15m. Japan has 210,000 small earth-fill dams and many of them are located in Hyogo prefecture. The number exceeds 40,000. Many small earth fill dams were constructed over a long period of history, and have played essential role in agriculture as valuable water source, because steep and short Japanese rivers water is not a stable source of water for rice farming. However these old earth-fill dams have been faced with disasters by earthquakes and typhoons, because Japan is an earthquakeprone country. Therefore, prompt reconstructions on these aging dams are required. In the reconstruction, the soil materials for impermeable core zone are required. However expensive soil for the core zone has to be prepared because of a lack of suitable soil materials at the dam site. Additionally, these earth-fill dams that need repair have large deposit of muddy soil as shown in Fig. 1.
