Abstract
In Kagoshima Prefecture the pyroclastic flow deposits are widely distributed. Shirasu is a non-welded part of pyroclastic flow deposits and classified into sandy soil. Furthermore Shirasu is divided into the primary and secondary ones. The primary Shirasu forms the Shirasu plateau and the secondary Shirasu forms the alluvial plains along the coastal line. It has been found that the mechanical properties of Shirasu ground are qualitatively different from common sandy ground, but the data are not enough quantitatively to estimate the mechanical properties for design. In this paper several in-situ tests are carried out to estimate the mechanical properties of primary Shirasu ground, the obtained data are compared with those of common sandy ground and secondary Shirasu ground and the results are discussed.
