Dynamic Properties of Shirasu

The southern Kyushu area is covered by thick volcanics ashes called Shirasu. Because Shirasu is cohesionless and the densify is relative small, it has induced many disasters at the time of heavy rains and earthquakes. Recently, the constructions of earth dams is being planned in this area using Shirasu. So, we need to clear the dynamic properties of Shirasu for this plan. The experiments on the liguefaction of saturated Shirasu and the measurements of rigidity of compacted Shirasu are carried out in our laboratory. In this paper, these results are described.